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Behavioral Ecology Symposium '97: Lloyd


ON RESEARCH AND ENTOMOLOGICAL EDUCATION II: A
CONDITIONAL MATING STRATEGY AND RESOURCE-
SUSTAINED LEK(?) IN A CLASSROOM FIREFLY
(COLEOPTERA: LAMPYRIDAE; PHOTINUS)

JAMES E. LLOYD
Department of Entomology and Nematology, University of Florida, Gainesville 32611

ABSTRACT

The Jamaican firefly Photinus pallens (Fabricius) offers many opportunities and
advantages for students to study insect biology in the field, and do research in taxon-
omy and behavioral ecology; it is one of my four top choices for teaching. The binomen
may hide a complex of closely related species and an interesting taxonomic problem.
The P. pallens population I observed gathers in sedentary, flower-associated swarms
which apparently are sustained by the flowers. Males and females remained together
on the flowers for several hours before overt sexual activity began, and then pairs cou-
pled quickly and without combat or display. Males occasionally joined and left the
swarm, some flying and flashing over an adjacent field in a manner typical of North
American Photinus species.

Key Words: Lampyridae, Photinus, mating behavior, ecology

RESUME

La luciernaga jamaiquina Photinus pallens (Fabricius) brinda muchas oportunida-
des y ventajas a estudiantes para el studio de la biologia de los insects en el campo
y para la investigaci6n sobre taxonomia y tambien sobre ecologia del comportamiento;
es una de las cuatro opciones principles elegidas para mi ensefanza. Este nombre bi-
nomial puede que incluya un complejo de species cercanamente relacionadas, que es
un problema taxon6mico interesante. La poblaci6n de P. pallens que observe se reune
en grupos sedentarios asociados con flores los cuales son aparentemente mantenidos
por dichas flores. Machos y hembras permanecieron juntos sobre las flores por varias
horas antes de que evidence actividad sexual comenzara, y luego las parejas se apa-
rearon rdpidamente sin combat ni exhibici6n. Los machos ocasionalmente se junta-
ron y abandonaron al grupo, algunos volando y alumbrando sobre un campo contiguo
en una forma tipica de las species norteamericanas de Photinus.




As in days agone, I take certain truths to be self evident: 1) that the connection be-
tween academic research and teaching is that professors who do research maintain their
intellectual interest in scholarship and infect their students with a passion and love for
a lifetime pursuit of knowledge; 2) that students properly taught become living reposi-
tories of this civilizing Ideal of western culture; and 3) that a true academician under-
stands the expression "publish or perish" to mean that he publishes to give evidence that
he has not mentally perished, and thus failed in his unique and special responsibilities
to his students and civilization. It is in this context that I introduce fireflies that I have
met, and suggest research that students can conduct, through Letters similar to those I
use as substitutes for lectures in my firefly courses. The one offered here follows through
on an observation that I made in last year's symposium (Lloyd 1997), that insect taxon-

















Florida Entomologist 81(3) September, 1998


omists in particular have a wealth of anecdotes and observations, and even "thumbnail"
studies, that can be useful to students and phenomenon-oriented biologists-in keeping
with John Sivinski's original introduction to this symposium series. This sketch con-
cerns the quest for an explanation for the long-puzzling congregations of a Jamaican
firefly, and for an evolutionary connection between the mating behavior of this firefly
and that of its mostly prosaic North American congeners.
One of the puzzles that confronted early fireflyers was the significance of the huge
swarms of sedentary fireflies that were reported to occur in some exotic places in the
world such as southeast Asia and Jamaica. Once pioneer Frank McDermott had dis-
covered how the flash signal system operates in North American fireflies (McDermott
1917, see Lloyd 1990), sexual attraction in fireflies was understood to be a one-on-one
operation. (Recall that in general, the male firefly searches throughout his habitat/
site while flashing his species-specific signal, and when a female of his species sees,
from her perch below, the appropriate signal [flash pattern] she flashes an answer,
and the two maintain a pattern-answer dialogue until he reaches her.) Thus, while the
huge gatherings and displays of Pteroptyx fireflies long reported to occur along tidal
rivers and in mangrove swamps in southeast Asia made little sense, the swarming of
a Photinus firefly in Jamaica was probably even more inscrutable-should not a
Photinus species, no matter where it occurred, follow the same general signaling rou-
tine and mating protocol? What were the Jamaican Photinus doing? Specifically, if
their gatherings actually were mating swarms, how did such a signaling system work,
with such visual cacophony and all?; and, what was the evolutionary connection be-
tween such behavior and the general pattern observed in Photinus species in North
America?
After the 1985 FES meeting in Jamaica I had a chance to spend a week in the field
with this enigmatic firefly, and make observations on swarms along the Rio Grande
River, between the Blue Mountains and the John Crow Mountains (Fig. 1). There were
many gatherings in the trees and fallow fields along the river and the road that fol-
lowed it up toward the highlands. The following Letter outlines key observations, pro-
vides tentative answers for the two basic questions, and suggests a working model for
P. pallen's mating system. In the future Lesley Ballantyne and I will publish data on
morphological comparisons and luminescent emission patterns.
The Internet (electronic) publication of this paper has additional figures as Au-
thorLink attachments to illustrate the text; these are color slides of the study region
and site, and various firefly behaviors. These are cited in text here by their number as
ALR figures. For example, the figure citation in the proceeding paragraph should read
(Fig. 1; ALR 1998, fig. 1) because the first AuthorLink illustration is a view of the Rio
Grande River and the road paralleling it. Legends for AuthorLink figures are included
here in this printed version in the End Notes section. These copyrighted illustrations
may be used freely with this citation: J. Lloyd, Univ. of Florida.


LETTER 23
THE UNIQUE MATING BIOLOGY OF
A CONGREGATING FLOWER-LOVING FIREFLY

Dear Fireflyers, the Jamaican firefly Photinus pallens (Fabricius) is one of the
most interesting and curiously different species that you may ever see, and it is the
best reason for going to Jamaica that I can think of. What sets P. pallens apart is that
its sexual behavior is very different from anything yet found in any species, in Ja-
maica or any place elsewhere in the Americas. Recalling lessons on the comparative
method in biology, this means that this firefly can provide an interesting exploration

















Behavioral Ecology Symposium '97: Lloyd


into "adaptive" radiation, and may reveal subtle elements in the behavior of other
Photinus that we now observe, but don't really see.
P. pallens is certainly one of the "World Class Big Four" apropos of firefly research
opportunity, and I have several arguments in support of this nomination. 1) It has the
richest, most complex mating protocol yet seen in any Photinus species, for it appar-
ently involves a conditional sexual strategy, prolonged mate evaluation, conspicuous
mutual luminescent displays with "obvious" resource acquisition, and perhaps bipa-
rental investment in offspring; 2) this flower-loving firefly with its esoteric sexual
charm, commonly occurs in easily accessible, sedentary, and manipulatable swarms-
I saw populations numbering in the thousands in fallow fields on the blossoms of the
introduced Asian ginger-lily-and the fireflies show varying degrees of site fidelity,
which seemingly is related to the number and nutritional value of the arena-plant's
blossoms.
3) P. pallens is a large and robust firefly, and this makes field observation easier
and permits marking for individual recognition, and it also simplifies dissection for
analyses of individual mating and nutritional conditions that may be connected with
mating behavior; 4) P. pallens is widely distributed in time and space, can be found
throughout Jamaica and the year (Fig. 1), and it is easily identified by non-coleopter-
ists (Fig. 2); it is readily located in the field and described to residents if help is needed
in finding active populations; and 5) P. pallens has a taxonomic mystery about it, for
though I have referred to it in the singular, as "it", so-called P. pallens may actually be
an array of closely-related species, incipient species, and sister and cousin popula-
tions, diverging through mechanisms of sexual preference while in micro-geographic
and/or temporal isolation. On a trip to Jamaica in the 1960s I observed and recorded
"a P. pallens" with a completely different flash pattern and saw no huge gatherings of
them.
My first doctoral student, Ed Farnworth, reviewed what was known about P. pal-
lens when he made an extensive study of Jamaican fireflies (1973), and made a num-
ber of observations on its behavior, ecology, and distribution. He pointed out the
fragmentary nature of current knowledge, alluded to the complexity of the puzzle,
and suggested that what was needed were detailed observations on the behavior of lo-



Montego Bay Cmfor Catle

ae a "


eg (9* Q
Negril a7" )C


K - Kingston
S 0 mi ~\lillhank

Fig. 1. Known localities of Photinus pallens (s.l.) in Jamaica. Elevations range from
sea level to 5000 feet; there are records for every month except May. Records are pri-
marily from Farnworth (1973), but also Leng and Mutchler (1922), and personal ob-
servation. The circled dot at the eastern end of the island, in the valley of the Rio
Grande River between the Blue and John Crow Mountains, is where the observations
reported here were made, near the villages of Comfort Castle and Millbank.

















Florida Entomologist 81(3) September, 1998


cal populations. In August of 1985 the Florida Entomological Society held its annual
meeting in Montego Bay, and after the required formalities and speeches, two of us
took to the hills, "your present author" with the P. pallens puzzle firmly in mind. I
found a good population in a ginger lily field between Comfort Castle and Millbank,
on the Rio Grande River at an elevation of about 1000 feet-but this jumps ahead in
the story.
From the literature and my observations it is clear that P. pallens congregates on
many different plant platforms: almond, rodwood, jointers, water mahoe, thistle, and
others, and sometimes in such numbers that the apparition of a swarm can be seen
from some dark distance. I saw several in trees along the creek called the Rio Grande
River, and could see their light from distances nearly as great as the combined lengths
of two football fields. Commonly such gatherings occupied only a portion of a tree, a
single branch, or a discrete "patch" in the foliage, but sometimes the entire crown of
a tree was occupied with flashers.
Though they occurred on a wide variety of plants and foliage types, walking along
stems and on and around the edges of leaves, it was clearly the blossoms of the plants
that were of special importance, for on them males and females remained motionless
with their mandibles buried in the flower parts. This resulted in an interesting illusion
when you looked up through the foliage of ajointers tree; individual flashing lights on
the vegetative parts of the tree were separated and in motion, but points of light on the
flowers were clustered and fixed along the elongate, curved spikes (Fig. 3; ALR 1998,
fig. 2), and appeared as scattered Pleides star constellations in a fluid universe.
With respect to the initial formation of a swarm there can be little doubt that a sin-
gle flashing individual can seed a gathering. Flashers on a patch of low grass as in a
pasture, captives in spiders webs (ALR 1998, figs. 3-5), and even the red-filtered light
of a head lamp being used by an entomologist who was digging singing crickets out of
their burrows, attracted P. pallens. Though swarms formed easily, only those with
flowers were sustained for very long. At blossom-rich sites such as jointers trees and
ginger lily fields (ALR 1998, fig. 6), many fireflies could be seen at dusk entering the
flower-arena from daytime retreats in the grass beneath the plants; "certainly" these
were swarmers from the previous night rejoining their swarm.
The Comfort Castle-Millbank region was a mosaic of agricultural and fallow fields,
with borders of tall grasses and other herbs and hedgerows of various trees and
shrubs. The study-site was a patch of the invasive Asian wildflower, the ginger lily
(Hedychium corium; ALR 1998, figs. 6-7). Each flower spike had several blossoms, but
it was the recently-drooped petals of mid-level flowers, not the top fresh nor the se-
verely withered ones at the bottom of a spike that the fireflies chose to stand on and
sink their mandibles into (Fig. 4). Curiously, these petals were of about the same pale
color as the fireflies themselves (Fig. 4; ALR 1998, figs. 8-10), and a naturalist's reflex
would be that a protective coloration model could be proposed-but, considering the
relatively recent introduction of the flower and that the beetles do not remain on the
flowers during daylight, this is not likely. The site I finally chose to watch had been a
taro field, was about 50 by 75 feet in dimensions, and had been plowed but not disked
(harrowed) level, and with its corduroy ridges and ditches it often put me down upon
my knees in the dark. Immediately adjacent to this patch was a 5-acre taro field (Colo-
casia esculenta, dasheen), over which P. pallens males flew, primarily very late at
night, as I will soon describe.
Flashing began at the ginger-patch at dusk, in dark, well-shaded places at the
ground beneath the fairly dense canopy of lilies and large leaves. Then, three to five
minutes later flashing had moved up onto the flowers. As darkness deepened, a few
fireflies flew in and landed on the flowers, and for a few minutes at twilight unlit flyers
could be seen by silhouette. During the first hour of flashing there was some move-












Behavioral Ecology Symposium '97: Lloyd


I,


























Figs. 2-5: 2. Habitus of Photinus pallens; a carbon dust drawing by Laura Line. 3.
Flowering spikes of a jointers tree, with six P. pallens at the blossoms. 4. Five P. pal-
lens on wilted petals of a ginger lily. 5. A male P. pallens mounted on a female. Note
the difference in lantern topography.

















Florida Entomologist 81(3) September, 1998


ment within the patch, as fireflies glowingly flew from perch to perch, and occasion-
ally even several yards out from the swarm before returning to a flower-spike perch.
Contrary to what you might expect, fireflies and other beetles are not necessarily
clumsy bunglers when it comes to flying, and they sometimes fly to and from perches
in very dim light with considerable precision. On the Pacific island of Espiritu Santo
I once saw a large luminescent click beetle fly slowly up to the top wire of a barbed-
wire fence, illuminating it with his ventral light-organ, and delicately land on the
wire-the equivalent of landing a rowboat in the dark, on a powerline, crosswise, us-
ing a kerosene lantern!
Here are a couple of examples of field notes that I made during early firefly flight
at swarm trees and the ginger patch: "glow start 2' out, go in and land. See another
start and fly few feet to another spot ... rise with glow, go 1 m up, go 3 m and arc down
... 4 m high, arc back, fishtail ... male fly from 1 plant to another, like a projectile
trajectory. Like [as though] thrown .." During the first hour of activity many fireflies
joined the swarm from elsewhere: "watch glower approach firefly tree. 80' out ... as
it got closer it got brighter ... one in from outside [above], made a corkscrew for 4 cy-
cles, 5" diameter ... long glow 1/4 bright, 10-15' out, went in to tree and landed ...
occasionally see glower coming down, not know if a recruit coming in or one changing
positions . ." There also were exchanges between the swarm and nearby vegetation:
"out from tree, flew around periphery in meandering zigzag course, and landed in an
adjacent tree ... out from tree, glowed and glowed, gradually touched down, 1 m high
vegetation 2 m out from tree .. ."
Male flash patterns were of two major types, excluding landing flashes and glows.
Males that were perched in swarms emitted fairly short flashes at very irregular in-
tervals. In trains of these flashes, a few or several pulses were given in rapid succes-
sion and then the rate slowed and they were emitted at irregular and longer intervals.
Whether each male has his own individually unique train, a signature you might say,
remains to be seen. Occasionally, a flashing male on a flower walked about with his
tail turned down. This resulted in his light being directed forward, and it also dragged
his abdomen tip along the substrate; perhaps chemical signals and markers were be-
ing deposited?
When P. pallens males flew over the nearby taro field they emitted bright flash pat-
terns, consisting of a single flare-like flash. (Such flashes were only uncommonly emit-
ted by perched males or those mounted on females.) Photo-multiplier analysis of these
flashes revealed them to be symmetrical in form, and to average about one-quarter
second in duration; they were emitted at roughly 3-sec intervals. One would obviously
presume that these flashes are comparable to the flash patterns emitted by mate-
seeking males of our North American Photinus species. Males flying over the taro
could be attracted to a penlight by answering their flash patterns with a quarter sec-
ond flash immediately after their flash, which probably approximates their females'
responses.
Females in swarms emitted trains of flashes that were visually indistinguishable
from those of males. However, photomultiplier-recordings reveal some differences and
careful analyses of lengthy, continuous pm-records are needed. There is one curious
aspect of male and female flashing that I find especially interesting, and revealing.
The sexual difference in light-organ topography of Photinus fireflies is well known;
the lantern of males occupies two ventral segments and that of females, only a portion
of one segment. As expected, when P. pallens males emitted flaring flashes they
flashed both segments of their light organ brightly. But, when perched and emitting
flash trains males emitted light from only one segment of their lantern. And, when
this segment was flashed, light sometimes seemed to scintillate across or race around
it, and sometimes only the middle section of it was illuminated. In other words, when















Behavioral Ecology Symposium '97: Lloyd


perched and flashing in swarms, males and females have similar emission surfaces-
and luminous output(?). Thus the loudness of a male's statement is seemingly not of
importance to him as he (apparently) competes in each little flower group, nor is his
light a competing beacon for the attraction of passing females. The whispered mes-
sages of twinkling fireflies on the flowers are a key to the mating system, and it is
their meaning that we must seek, to understand P. pallens communication and mat-
ing system.
From time to time when watching fireflies and stumped for what to do next, as a
matter of habit I compulsively quantify; it may help me see and think. I counted sta-
tionary points of light in the ginger-patch by slowly scanning across the top of the
arena, punching a hand tally counter with my thumb and pointing through (azimuth)
space with the index finger of the tallying hand. When I compared scan-samples of
flashes with actual beetle counts for several flower-spikes I found that there were 4-5
times more fireflies flashing than I could count from my stand (a 1-ft earthen hum-
mock), which would indicate that sometimes more than 2,000 fireflies could actually
have been present in the ginger lily patch!
I made such scan samples of flashing P. pallens at various times during several
nights (Fig. 6). They began flashing on the flower spikes about 30 minutes after sun-


450
S-X- pml3
400 -- am14
-- pml5
350 ,. - pm16

3001 '. A A v pm17
A ,, jii dmls
250- a.* hP








0- light rain on 18th
I-I. .I . . ..
1 130 ;

:1)0 S \hard rain start
50 \ / n-idnight
; ^ light rain on 18th 4
0 5 10 15 20 25 30
sunset Time of Night (creps; 1 = 22 min)

Fig. 6. Scan samples of fireflies flashing in the ginger lily field at various times dur-
ing five nights. Flashing on the flower spikes began about 25 minutes after sunset,
though flashing could be seen in the deep shade at the stem bases a few minutes ear-
lier. An activity peak occurred shortly after midnight (ss + 390 min.) and activity then
fell off, ending about 30 minutes before sunrise-about the time birds began singing.
The biggest night was on 16 August (pml6). The last two days of observations had the
least activity: one followed a warm, dry day, the other, an overcast day with light rain;
perhaps the ginger blossoms or the "season" of mating activity in the local P. pallens
population had reached a peak and was falling off.

















Florida Entomologist 81(3) September, 1998


set, and the number flashing rose sharply for the next 20+ minutes. Such flashing
peaked about midnight (sunset + 360 min.) and completely ended about 25 minutes
before sunrise (ss+650). At the end, with the dawn singing of birds, nearly all of the
fireflies had left the flowers, most of them apparently having moved down the stems
and out of sight, for I saw none in flight.
Up till now though I have alluded to reproduction, and we have come to expect sex-
ual behavior whenever we see adult fireflies flashing, I have not actually mentioned
intromission or the physical flowing of sperm and genes. Your suspense should have
been mounting, and now it is time for P. pallens males to successfully do so-keep in
mind that the time of mounting and mating in a local population or swarm could be
of considerable significance for recognizing local subpopulations and even presently
unrecognized sibling/sister P. pallens species.
In another quantification routine, I carefully scrutinized a "trap-line" of (tagged
and numbered) individual flower-spikes (ALR 1998, fig. 7) at various times during the
night from dusk till dawn seeking recognizable sexual activity. I finally saw it, and it
began late, ca 200 minutes after sunset. Before this time of night, though "pairs" were
often especially close together, mandibles buried in the same withering petal-even
with cuticles touching and standing head-to-head, side-by-side, or lying across each
other-nothing conspicuously sexual was noted. In fact, flower-spike samples of
"touchy-touchy pairs" had various sex combinations, male/male and male/female and
female/female.
Recognizable sexual pairing began when males actually mounted females (Fig. 5),
and probed their terminalia with extruded aedeagi (ALR 1998, fig. 8). Males some-
times repeatedly inserted and withdrew the tip or distal portion of their aedeagus
(ALR 1998, fig. 9), and at such time both individuals often flashed continuously. Per-
haps it is such flashing that is responsible for an increase in overall flashing that
seems to occur at about ss + 180 (Fig. 6). Also, at such times males sometimes emitted
flare-like flashes, and mounted flaring males could be spotted from some distance in
the ginger patch-could such flaring be "desperation arguments" being used on reluc-
tant females? (But this suggestion biases expectations-perhaps it is the males that
are the discriminating mate choosers?) The flare-flash has the same form and apparent
intensity as the flare-like flash patterns that are emitted over the adjacent taro field.
Females easily avoided intromission by bending the tip of their abdomens downward.
Copulation was first observed at ss + 317 minutes (Fig. 7; ALR 1998, figs. 9-10),
and sketchy notes and fragmentary observations suggest that pairs may remained at-
tached even until dawn. Soon after connecting, pairs rotated to a tail-to-tail copula-
tion position, and some abandoned the flower petals for adjacent foliage and bracts,
with one partner dragging the other backward (ALR 1998, figs. 11-12). At a dawn
count, coupled pairs separated abruptly at a touch of their flower or when illuminated
by the beam of the headlamp. Males that were rejected apparently did not remain
mounted long nor show aggressive behavior toward other males, though I once saw a
male briefly butt another that was mounted on a female.
From the aerial traffic I observed it would appear that male P. pallens sometimes
left their ginger patch flowers and behaved like other ("normal") Photinus, seeking fe-
males via search over adjacent fields. The temporal appearance of this behavior sug-
gests that there was an intimate and functional relationship between the two activity
spaces, between the ginger lily arena and the taro field, and that these two tactics are
part of a conditional sexual strategy in this flower lover-conditional in the sense that
on condition of mating failure on the flowery platform, or failure to find a swarm, a
male ("flashingly") takes to the air to seek a mate afield.
Male P. pallens flew over the taro field at altitudes up to 15 feet and their flash pat-
terns could be seen at distances of 75 or more yards. I made a few scan-samples of















Behavioral Ecology Symposium '97: Lloyd


zeroes 3 3 1 3 3 3 3 1 1
counts 3 3 1 4 6 7 6 3 2 1 2 1
S- 25

40- ( -- Couple
35 ....... Mount .0 -20

30-
S -15 O
E 25- =
El Couple
20 -
[ Mount 10
S15

S Midnight = 14.9 creps -

0 -
5-

01 i i i 0
3 5 7 9 11 13 15 17 19 21 23 25 27 29
Time of Night (creps: 1 = 22 min)

Fig. 7. Number and time of overt sexual activity observed on a sample of ginger lil-
ies. Left Y-axis shows total number (bars); right Y-axis shows mean number (lines and
symbols). X-axis shows time of night, with sunset at zero and sunrise at about 30 crep
units. Numerals at the top indicate the number (n) the mean was based on, and the
number of times no (zero) mounting or copulation was observed in the indicated time
bracket.


these airborne flash patterns at various times during five nights. This behavior began
about the same time that flashing began in the ginger lily patch, but it remained at a
low level until ss + 300, about 30 minutes before midnight, when it increased sharply.
My few scattered (in time) samples after ss + 400 indicate that a dramatic, even 15-
fold increase may have occurred over the field (Fig. 8). However, it should not neces-
sarily be concluded that such "normal-type" Photinus behavior is typically, primarily,
or obligately confined to the hours after midnight. I saw many P. pallens males afield
at other sites along the road early in the evening.-As a bare-bones working notion:
perhaps males that close in isolation search early in the evening in "typical Photinus
fashion" until they see the light of a swarm, and males in a swarm may leave it after
they determine that their chances of sexual success there are poor. Note that the scan
sample data show that the rise in taro search activity occurred at about the time that
definitive sexual pairing began on the ginger lilies (compare Figs. 7 and 8).
I began this Letter with two questions about the puzzling flashing and swarming
behavior of P. pallens: (1) what were the Jamaican Photinus doing, and if their gath-
erings were mating swarms, how did such a mating system work?; and (2) what was
the evolutionary connection between such behavior and that of Photinus species ob-
served in North America? The flow chart in Fig. 9 is a sketchy working model of how
the mating system may operate, and provides an obvious answer to the first ques-

















270 Florida Entomologist 81(3) September, 1998


80-




60-
iS



| 50-

40- i
-Midnight
30 = 14.9 creps I

20-
-. 20- I *


S10
e 4


0 5 10 15 20 25 30

sunset t Time of Night (creps: 1 = 22 min)

Fig. 8. Scan samples of male P. pallens emitting flash patterns over the taro field
adjacent to the ginger lily study patch. Males flew up to 5 meters in altitude and emit-
ted their single bright flashes each 2-4 seconds. The beginning of the sharp rise at
about 12 creps coincides with the onset of overt sexual activity in the adjacent ginger
lily field. Curve segments drawn by eye.


tion-in the flower-borne swarms fireflies find and observe prospective mates and
they take on food and water.
The answer to the second question is problematic. We can see that to make a rea-
sonable evolutionary connection, an acceptable historical transition from a typical
Photinus to the P. pallens mating system, we need to insert a stage of lengthy precop-
ulatory association. We might be seeking a Photinus species that has prolonged pla-
tonic associations at watering or sapping or nectaring holes. Although adult fireflies
of various species are occasionally seen at flowers, and captives can be kept alive up
to a month by providing them with honey or slices of fresh apple, only the flower-lover
P. pallens has been found in nature in prolonged association with blossoms. You will
need to peek in on the lives and sexual behavior of species that seem to be P. pallens'
closest relatives, and pallens itself (i.e., s.l., in a broad sense) at other Jamaican re-
treats. Call your travel agent, and when you go, plan ahead to put identifying marks
on adults to see, for example, whether sexual associations endure more than one
night; and to provide artificial blossoms with various kinds of enriched (e.g., carbohy-
drate, protein) "juices" to see if they are especially valued; and to see whether mole-
cules of nutrients that males imbibe from flowers wind up in the eggs that their mates
lay-could this actually be what the long-delayed copulation and mate choice is all
about? Personally, I am most curious about the possibility that the trains of flashes
emitted by perched males and females are individualized signatures, because this

















Behavioral Ecology Symposium '97: Lloyd


.. ............

warm Not Flying Flash
Develop
Dlop Patterns: Mode 1




-TSwarim" r
Begins, GrOWS En Swa
Enduring Swarm
SMany/Rich(?) Flowers,

observe/monitor prospec-
S\ tive mates, meet old
flame (????)
Solitary Perchedl w\ s
N t F*




. : s . . . . . . . . .
During Daylight Remain On
Cround Under Low Herbs/Cras~ :--
SBeneath/Near Enduring
SEclose Swani Teree (Flowers)


--------Oviposit
-~*' Oviposit


Fig. 9. Flow chart model of P. pallens sexual behavior, integrating observations at
the ginger lily patch, the taro field, and other sites in the Comfort Castle-Millbank re-
gion along the Rio Grande River.


would connect with other insect behaviors I have found puzzling (Lloyd 1981). And,
my thoughts return again and again to the fundamental taxonomist's question-just
how many P. pallens species are there throughout Jamaica and her calendar?

ENDNOTES

I thank John Sivinski and Steve Wing for reading the manuscript. Florida Agricul-
tural Experiment Station Journal Series Number R-06152.
The following enumerated statements are figure legends for color illustrations
(slides) that appear as AuthorLink attachments to this article in the electronic publi-
cation of this issue of the Florida Entomologist, and which are cited in text here as
ALR 1998, fig.#: 1. A view southeast along the gravel highway and upstream toward
the Highlands. The Rio Grande River flows in the valley between the Blue Mountains
and the John Crows. 2. Curved spikes on ajointers tree with feeding or sipping P. pal-
lens. 3. A flashing Photinus pallens hanging and being wrapped in a spider web. The
flashes of single fireflies in webs or on the ground, and even continuous emissions of
light as from a flashlight attract P. pallens. 4. A patch of grass atop a hill above the Rio
Grande River, where a few P. pallens gathered and flashed one evening. Apparently
swarms that form at sites without many flowers do not become large nor long endure.
5. Flashing Photinus pallens at flowers on a spike in the grass. Though a few fireflies
were attracted, large swarms were not seen at such sites. 6. A view of the ginger lily
patch. Samples of flashing fireflies in this field indicate that 2000 or more may have

















Florida Entomologist 81(3) September, 1998


been present. Note the red plastic tags here and there. These mark flower spikes that
were periodically sampled for firefly sexual activity. 7. A tagged ginger lily spike num-
ber 10, in the series of spikes that was sampled for sexual activity. 8. A mounted P. pal-
lens male with extended aedeagus probing the abdomen tip of his mate to be. 9. The
male in 8 and 9 (above) with partially inserted aedeagus. This connection seemingly
indicates mate acceptance and requires the mechanical cooperation of both, though it
is of course conceivable that males have some coercive leverage or that females can
avoid using sperm that males have injected into them. 10. The connection (initiated
in 8 and 9 above) is now complete, judging from external appearances, though inside
the female's reproductive track there certainly are other significant events unfolding.
11. A pair partially rotated to a tail-to-tail position. 12. A pair has now completed ro-
tated to a tail-to-tail position. Such pairs sometimes leave their flowers, where their
lengthy(?) association presumably began, and remain on nearby leaves and bracts.
Note the sexual difference in light organ topography.

REFERENCES CITED

[ALR] Authorlink References. 1998. ALR references in this article are to supplemen-
tal information accessible through a World Wide Web hyperlink that is with the
article's listing in the online Florida Entomologist at http://www.FCLA.edu/
FlaEnt/.
FARNWORTH, E. G. 1973. Flashing behavior, ecology and systematics of Jamaican fire-
flies. PhD Dissertation, Univ. of Florida, 278 pp.
LENG, C. W., AND A. J. MUTCHLER. 1922. The Lycidae, Lampyridae, and Cantharidae
(Telephoridae) of the West Indies. Bull. American Museum Natural History. 46:
413-499.
LLOYD, J. E. 1967. Signals and systematics of Jamaican fireflies: notes on behavior
and an undescribed species (Coleoptera: Lampyridae). Entomol. News 80: 168-
176.
LLOYD, J. E. 1981. Sexual selection: individuality, identification, and recognition in a
bumblebee and other insects. Florida Entomol. 64: 89-118.
LLOYD, J. E. 1990. Firefly semiosystematics and predation. Florida Entomol. 73: 51-
62.
LLOYD, J. E. 1997. On research and entomological education, and a different light in
the lives of fireflies (Coleoptera: Lampyridae; Pyractomena). Florida Entomol.
80: 120-131.
MCDERMOTT, F. A. 1917. Observations on the light emission of American Lampy-
ridae: the photogenic function as a mating adaptation. Fifth paper. Canadian
Entomol. 49: 53-61.

















Behavioral Ecology Symposium '97: Epsky and Heath 273

EXPLOITING THE INTERACTIONS OF CHEMICAL AND
VISUAL CUES IN BEHAVIORAL CONTROL MEASURES FOR
PEST TEPHRITID FRUIT FLIES

NANCY D. EPSKY AND ROBERT R. HEATH
USDA/ARS, Center for Medical, Agricultural and Veterinary Entomology
1700 SW 23rd Dr., Gainesville, FL 32608

ABSTRACT

Traps for tropical pest tephritids have relied primarily on chemical cues while
traps for temperate pest tephritids have relied primarily on visual cues. Here we re-
view research on the interactions between chemical and visual cues that have been
observed in the development of traps for the tropical Mediterranean fruit fly, Ceratitis
capitata (Wiedemann), and the temperate apple maggot, Rhagoletis pomonella
(Walsh). By exploiting these interactions, it may be possible to produce efficacious
trapping systems that could be used in a behavioral approach to fruit fly population
control.

Key Words: Tephritidae, Ceratitis capitata, Rhagoletis pomonella, trapping, phero-
mone, bait

RESUME

Trampas para plagas de tefritidos tropicales han dependido principalmente de se-
nales quimicas mientras que trampas para plagas de tefritidos templados han depen-
dido principalmente de senales visuales. Se revisan investigaciones sobre las
interacciones entire senales quimicas y visuales que se han observado en el desarrollo
de trampas para la mosca del Mediterraneo, Ceratitis capitata (Wiedemann), de luga-
res tropicales y para la mosca de la manzana, Rhagoletis pomonella (Walsh), de luga-
res templados. Aprovechando estas interacciones desde un enfoque de
comportamiento, es possible crear sistemas de trampeo eficaces para controlar pobla-
ciones de moscas de la fruta.




Trapping systems for insects are important components in integrated pest man-
agement programs. Trapping data are used to make decisions on the initiation or ter-
mination of control measures, as well as to assess efficacy of control approaches that
have been implemented. With the availability of sufficiently effective traps that cap-
ture both female and male pest insects, trapping systems may be used as behavioral
control measures and, thus, could be added to the growing list of biologically-based
technologies for insect control (U.S. Congress 1995). Adults of tephritid fruit flies use
visual and olfactory stimuli to locate hosts (reviewed in Prokopy 1986), and both vi-
sual and chemical cues have been used in traps for pest tephritid fruit flies (reviewed
in Cunningham 1989a, Economopoulos 1989). Traps for tropical tephritids, such as
the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), have relied primarily on
chemical lures (Gilbert et al. 1984), while the traps for temperate tephritids, such as
the apple maggot, Rhagoletis pomonella (Walsh), have used visual cues (Prokopy
1968). In this paper, we will 1) review fruit fly traps that use either chemical or visual
cues alone, 2) discuss the interactions that may occur among different cues associated

















Florida Entomologist 81(3) September, 1998


with traps for fruit flies, and 3) explore the ability to exploit the interactions between
these cues to provide powerful trapping systems for pest fruit flies.

CHEMICAL CUES AND VISUAL CUES USED INDEPENDENTLY

Chemical Cues

Some of the earliest trapping systems for pest fruit flies relied on the use of baits
made from proteins and fermenting sugar (Gurney 1925). Numerous substances have
been tested, and a corn protein hydrolysate was found to be most effective for capture
of C. capitata (reviewed in Roessler 1989) while yeast hydrolysates were found to be
most effective forAnastrepha species (reviewed in Heath et al. 1993). These baits are
usually deployed in McPhail traps (Newell 1936), which are bell-shaped invaginated
glass traps with a water reservoir, or other bucket-type traps (reviewed in Cunning-
ham 1989a). These protein-baited traps capture both female and male fruit flies.
Male-specific synthetic chemical attractants have been discovered for tropical tephrit-
ids in the genera Ceratitis and Bactrocera (reviewed in Cunningham 1989b). These at-
tractants are called parapheromones because they cause responses similar to true
pheromones, but they are not produced by the responding species. Trimedlure, tert-
butyl 4 (and 5)-chloro-2-methylcyclo-hexane-l-carboxylate (Beroza et al. 1961), is a
highly effective, commercially available parapheromone for male C. capitata. Methyl
eugenol (Howlett, 1915) and cue-lure (Alexander et al. 1962) are parapheromones
that are attractive to males of oriental fruit fly, Bactrocera dorsalis (Hendel), and the
melon fly, Bactrocera cucurbitae (Coquillett), respectively, as well as other Bactrocera
species. Parapheromone lures are typically mounted in Jackson traps (Harris et al.
1971), which are white triangular cardboard traps that contain a sticky insert placed
on the floor of the trap (Gilbert et al. 1984).

Visual Cues

Fruit flies use a number of visual cues to locate hosts, and appropriate visual cues
may be highly attractive to pest Tephritidae (e.g. Prokopy 1968). Numerous studies
have examined the effect of shape, size and color of visual stimuli on fruit fly response
(reviewed in Katsoyannos 1989). Prokopy (1968, 1972, 1973) demonstrated that more
R. pomonella were captured on fluorescent yellow rectangles and on enamel red
spheres than on other shapes in different colors. He hypothesized that the flat surface
of the rectangle together with the fluorescent color represented leaf-type stimulus
that elicits food-seeking and/or plant-seeking behavior, whereas spheres constitute a
fruit-type stimulus that elicits oviposition and/or mating-behavior. More C. capitata
were captured on yellow rectangles than light orange, light green, red, gray or clear
rectangles (Prokopy and Economopoulos 1976). Nakagawa et al. (1978) tested re-
sponse of C. capitata to a wide variety of shapes and colors. In tests among 7.5-cm
spheres of different colors, black and yellow captured the most females and black, yel-
low, red and orange captured the most males. Among spheres, cylinders, rectangles
and cubes of equal surface area (175 cm2) painted black or yellow, the black or yellow
spheres caught the most of either sex. Among black or yellow spheres ranging in size
from 1.5-to 18-cm diam, the black 1.5- and 3.2-cm spheres were two times more effec-
tive than equal sized yellow spheres, the black and yellow 7.5-cm spheres were
equally effective, and the yellow 18-cm spheres were more effective than black 18-cm
spheres. The yellow 18-cm spheres were most effective over all. Greany et al. (1977)
found that fluorescent orange rectangles were the most effective for capture of the

















Behavioral Ecology Symposium '97: Epsky and Heath 275

Caribbean fruit fly, Anastrepha suspense (Loew), and that most of the flies captured
were sexually mature females (Greany et al. 1978). Sivinski (1990) found that more
male A. suspense were captured on 20-cm diam. orange spheres than spheres that
were smaller or differently colored, but that female flies were trapped equally on 20-
cm diam. green spheres. Green, yellow and orange were the most attractive colors for
the Mexican fruit fly, Anastrepha ludens (Loew) (Robacker et al. 1990), but females
preferred large spheres over large rectangles and small rectangles over small spheres
(Robacker 1992).

CHEMICAL CUES THAT INTERACT WITH VISUAL CUES

Addition of Visual Cues to Chemical Cue-Based Standard Traps

In the section above, we discussed examples in which the chemical cues and visual
cues were used independently of other cues. Protein baits are often used in glass
McPhail traps, so the only potential visual cue is the brown color of the bait. Similarly,
trimedlure is widely deployed in white Jackson traps and can also be used success-
fully in clear traps such as a Steiner trap (Steiner 1957, Nakagawa et al. 1971). Stud-
ies have shown, however, that the addition of a visual cue to these chemical cues can
increase fruit fly capture. Liquid protein-baited glass McPhail traps painted fluores-
cent yellow captured more fruit flies than unpainted McPhail traps or McPhail traps
painted enamel yellow, red or gray (Prokopy and Economopolous 1975). There are sev-
eral plastic McPhail-type traps used currently in fruit fly detection that use a yellow
base as a visual cue (e.g., Katsoyannos 1994). Similarly, use of a fluorescent color in-
sert instead of a white insert in trimedlure-baited Jackson traps increased C. capitata
capture during certain times of the year in field trials conducted in Guatemala (Epsky
et al. 1996). Trimedlure-baited yellow panels are used in a high-density trapping pro-
tocol when outbreaks of C. capitata are detected in the continental United States
(Lance and Gates 1994), an example of combining a yellow visual cue with the chem-
ical cue to optimize fruit fly capture.

Addition of Chemical Cues to Visual Cue-Based Standard Traps

There is a complex of visual cues and chemical cues emanating from a host tree
that could provide improved capture of fruit flies, especially female fruit flies. Females
travel to host trees to find both food and oviposition sites. Females require protein to
ensure fecundity (Christenson and Foote 1960) and volatile chemicals released from
protein baits provide food cues to foraging females. One of the chemicals released from
protein bait is ammonia (Bateman and Morton 1981). Prokopy (1968) and Moore
(1969) found that addition of ammonia to red spheres did not increase capture of R.
pomonella over unbaited red spheres, however ammonia did increase capture on yel-
low rectangles. Prokopy (1972) hypothesized that the addition of ammonia to yellow
rectangles increased fly capture because the yellow rectangle elicits food-seeking re-
sponse and did not improve capture on red spheres because red sphere elicits prima-
rily oviposition and mating-related behavior.
Host fruit odor is a potential source of chemical attractants for females looking for
an oviposition site. Rhagoletis pomonella adults are attracted to the odor of fresh-
picked apples in the field (Prokopy et al. 1973), and to synthetic apple volatiles in lab-
oratory bioassays (Fein et al. 1982). In tests conducted in apple orchards, addition of
synthetic apple volatiles increased capture of flies when the lure was added to red
spheres, but not when added to yellow rectangles (Reissig et al. 1982). These exam-

















Florida Entomologist 81(3) September, 1998


ples demonstrate the importance of using the correct chemical cue and visual cue
combination for optimal fruit fly trapping.

Use of Chemical and Visual Cue Interactions to Develop New Trapping Systems

Pheromone Volatiles-Many of the tropical tephritids have male-produced phero-
mones that could potentially be powerful, specific attractants for female flies. Al-
though a number of putative pheromone components have been identified and have
shown activity in laboratory bioassays, they have generally been less than satisfac-
tory in field tests (Howse and Knapp 1996). An exception to this has been found with
the papaya fruit fly, Toxotrypana curvicauda Gerstaecker, which does not respond to
food-type lures such as protein (Landolt 1984) or sugar (Sharp and Landolt 1984).
Males produce a pheromone that is attractive to females (Landolt et al. 1985) and
chemical analysis determined that it is composed of a single component (Chuman et
al. 1987). Although female flies responded to synthetic pheromone in flight tunnel bio-
assays (Landolt and Heath 1988), attempts to capture papaya fruit flies with syn-
thetic pheromone alone were unsuccessful. Field observations noted possible
attraction to the chemical, but that flies would land on papaya fruit near the lure.
However, by combining the pheromone lure with an appropriate visual cue, i.e. a
green 12.7-cm diam. sphere that mimicked a papaya fruit, a trapping system for these
flies was developed (Landolt et al. 1988). Subsequent research found that a phero-
mone-baited green cylindrical trap could be as effective as a pheromone-baited sphere
(Heath et al. 1996a).
Over 60 components produced by calling male C. capitata have elicited electroan-
tennogram responses in female C. capitata (Jang et al. 1989). Black spheres baited
with three of the major components (ethyl-(E)-3-octenoate, geranyl acetate and E, E-
a-farnesene) captured more females than unbaited spheres in field tests conducted in
Guatemala (Heath et al. 1991). In subsequent flight tunnel bioassays, addition of a
fourth component (A-1 pyrolline) increased response of female flies over the three
component blend, however, response was less than response obtained with calling
males (Heath and Epsky 1993). Field tests of black spheres and cylindrical traps
baited with these synthetic blends captured few flies relative to traps baited with the
protein bait (R. R. H. and N. D. E., unpublished). Thus, there may be additional chem-
ical cues, visual cues or other cues needed to develop pheromone-based traps for fe-
male C. capitata. Presence of competing male fruit flies and host fruit may be
complicating factors (Howse and Knapp 1996).
Food Volatiles-We have been involved in developing food-based synthetic attrac-
tants for tropical pest fruit flies. Initial research involved a two component synthetic
attractant containing ammonium acetate and putrescine, and a cylindrical trap to
protect the lures from the environment (Heath et al. 1995). In field tests conducted in
Guatemala with wild populations of C. capitata, interactions between chemical cues
and visual cues were an important aspect of trap and lure development. In tests of
clear traps versus traps with a painted color strip (~7.5-cm high) around the periphery
of the middle to provide a visual cue, more female C. capitata were captured in green
traps than clear traps, with intermediate capture in orange or yellow traps. More male
C. capitata, however, were captured in yellow traps than orange traps, with interme-
diate capture in clear or green traps. We then compared green and orange traps baited
with a low, medium or high dose of synthetic attractant, and liquid protein-baited
McPhail traps. In these tests, capture of females in both orange and green traps baited
with synthetic attractant increased in relation to McPhail traps as dose of the syn-
thetic attractant increased. Females captured in these studies were dissected to deter-
mine mating status. Throughout these tests, 21-25% of the females captured in the

















Behavioral Ecology Symposium '97: Epsky and Heath 277

McPhail traps were unmated. However, 55 and 69%, respectively, of the females cap-
tured in the orange and green traps baited with the low dose of synthetic attractant
were unmated. In the same traps baited with the high dose of synthetic attractant,
percent unmated dropped to 13 and 4%, respectively. Thus, both the sex and the repro-
ductive state of the fly affected response to the visual and chemical cue combination.

Quantification of Chemical and Visual Cue Interactions
Studies conducted by Aluja and Prokopy (1993) quantified the interaction between
visual cue (color of fruit model) and chemical cue (concentration of synthetic host fruit
odor) in host finding by R. pomonella. They found that a direct relationship between
fruit odor concentration and fruit fly ability to find baited clear spheres (weak visual
cue), but that fruit odor concentration had no effect on fruit fly ability to find baited red
spheres (strong visual cue). Thus a high degree of interaction among cues may indicate
that the cues being evaluated could be improved further. For example, in our research
to optimize cylindrical traps baited with a two component food-based synthetic attrac-
tant (ammonium acetate and putrescine), we found numerous interactions between
visual cues and chemical cues (Epsky et al. 1995) and we used this information to op-
timize the trapping system (Heath et al. 1996b). Cylindrical traps with the painted
surface on the interior of the trap (presenting a smooth, shiny exterior to the fly) were
compared with traps with the painted surface on the exterior of the trap (presenting
a rough, dull exterior to the fly). Orange and green traps were baited with the medium
and high dose of the two component synthetic attractant, as were tested in previous
research by Heath et al. (1995). Significantly more females were captured on dull
green traps than on shiny orange traps at either dose and slightly more females were
captured on dull traps versus shiny traps of the same color. Additional interactions
were observed in tests with change in putrescine dose. In initial studies, putrescine
was formulated using polypropylene vials (1-cm i.d., 2.2-cm long). The vial formula-
tion was then compared to membrane-based putrescine lures with an exposed mem-
brane opening of either 3- or 5-mm diam. The exposed membrane opening governs the
chemical release rate, so the lure with the 5-mm opening releases a greater amount of
putrescine than the lure with the 3-mm opening. The putrescine formulations were
tested in green cylindrical traps with either a shiny exterior or a dull exterior that
were baited with ammonium acetate lures. Traps baited with ammonium acetate and
membrane-based putrescine lures captured the most C. capitata males and females.
Visual cue and chemical cue interactions were observed in that the best capture
among the traps with the shiny green exterior was with the 5-mm putrescine lure and
ammonium acetate lure, but among the traps with the dull green exterior the best cap-
ture was with the 3-mm putrescine lure and ammonium acetate lure.
Subsequent research discovered that trimethylamine is a potent synergist to ammo-
nium acetate and putrescine for capture of C. capitata (Heath et al. 1997). Traps baited
with all three components captured more flies than traps baited with ammonium ace-
tate and putrescine, and this was true whether it was tested in clear (glass McPhail
traps), light green, dark green or yellow traps (Heath et al. 1997, Epsky et al. 1998).
Thus, increase in potency of the chemical attractant by the addition of trimethylamine
lessened the interaction with the visual cue used in the trapping system. Presence of a
visual cue is still an important element in optimal trap performance for traps baited
with the three component attractant, however, choice of visual cue is less critical.

EXPLOITING INTERACTIONS FOR BEHAVIORAL CONTROL
Trapping systems have been developed primarily for use in detecting and monitor-
ing target insects. There is an increasing need to move from insecticide-based control

















Florida Entomologist 81(3) September, 1998


measures to biologically-based control measures (U.S. Congress 1995), and the devel-
opment of highly effective and selective trapping systems that target female fruit flies
could provide a mechanism for behavioral control through mass trapping to be used
alone and in conjunction with other integrated pest management systems. Experi-
ments conducted in Greece indicated that populations of C. capitata could be effec-
tively reduced when traps baited with liquid protein baits were deployed along with
traps baited with trimedlure (Zervas 1996). Citrus fruit was protected from infesta-
tion by immigrating populations of C. capitata using mass trapping in combination
with single-sex sterile male release (Economopoulos et al. 1996). In both studies, fruit
was protected without insecticide application. Prokopy and Mason (1996) demon-
strated protection of fruit from R. pomonella infestation by hanging sticky-coated red
spheres in close proximity to synthetic fruit odor and synthetic food odor around the
periphery of an apple orchard to intercept fruit flies immigrating into the orchard.
Although showing promise, these trapping systems do not provide the longevity
necessary for use in long-term, mass trapping applications. Either sticky material or
a water reservoir is used to kill attracted flies. Sticky surfaces quickly become deacti-
vated by the accumulation of target and non-target insects on the surface, as well as
by dust and debris that might be blown onto the trapping surface. Water-filled traps
may dry out or become filled with captured insects. The ideal mass trapping system
would last for 6-8 weeks and be essentially maintenance free during that time period.
An alternative approach is the incorporation of a pesticide instead of the sticky mate-
rial with the dry trap. A dry trap with the parapheromone methyl eugenol, mixed with
a pesticide, was used successfully to eradicate the oriental fruit fly in a male-annihi-
lation project (Steiner et al. 1965). Methyl eugenol is a feeding stimulant as well as an
attractant. Thus, oriental fruit fly males consume the pesticide-laden formulation and
obtain a lethal dose of pesticide. We developed a toxicant system that included a com-
bination of visual cue, feeding stimulant and a pesticide in a formulation that could
be applied in a relatively easy manner for use in traps as an alternative to sticky ma-
terial (Heath et al. 1995). Panels coated with this material were placed inside a cylin-
drical trap to kill flies that have entered the trap. This toxicant system is deactivated
if it is exposed to rain, thus compromising its use on the exterior surface of a trap
(Duan and Prokopy 1995a, 1995b). Recent research has been directed towards the de-
velopment of weather resistant, spatially localized toxicant-based bait stations. The
incorporation of a pesticide with female-targeted synthetic attractants and well de-
signed traps with appropriate visual cues into pesticide-bait stations would provide
powerful tools not only for monitoring but potentially for fruit fly suppression that
would avoid the environmental problems of pesticide bait sprays.
The availability of food-based synthetic attractants will afford a new dimension in
exploring the interactions among visual cues and chemical cues for pest fruit fly fe-
males. Previous efforts with food-based liquid protein baits were hampered by batch
to batch variability as well as by change in attractiveness of the bait over time (Epsky
et al. 1993, Heath et al. 1994). Liquid baits require use of a trap with a reservoir, thus
the ability to investigate interactions among chemical cues and visual cues using
these lures is limited. Increased knowledge of behaviors associated with attraction of
both sexually immature females and egg laying females will improve detection and
delimitation of pest fruit flies, and provide increased protection of crops adversely af-
fected by their presence.

ACKNOWLEDGMENTS

The authors thank Peter Teal, Robert Meagher, Jr. (USDA/ARS, Gainesville, FL)
and John Capinera (Dept. of Entomol. & Nematol., Univ. of FL) for reviewing an ear-

















Behavioral Ecology Symposium '97: Epsky and Heath 279

lier version of this manuscript. This article reports the results of research only. Men-
tion of a proprietary product does not constitute an endorsement or recommendation
for its use by the USDA.

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Florida Entomologist 81(3)


September, 1998


PHOTOTROPISM, BIOLUMINESCENCE, AND THE DIPTERA

JOHN M. SIVINSKI
Center for Medical, Agricultural and Veterinary Entomology
Agricultural Research Service, U.S. Department ofAgriculture, Gainesville, FL 32608

ABSTRACT

Many arthropods move toward or away from lights. Larvae of certain luminescent
mycetophilid fungus gnats exploit this response to obtain prey. They produce mucus
webs, sometimes festooned with poisonous droplets, to snare a variety of small arthro-
pods. Their lights may also protect them from their own negatively phototropic pred-
ators and/or be used as aposematic signals. On the other hand, lights may aid
hymenopterous parasitoids to locate fungus gnat hosts. The luminescence of mush-
rooms can attract small Diptera, and might have evolved to aid mechanical spore dis-
persal. Among Diptera, bioluminescence is found only in the Mycetophilidae, but the
variety of light organs in fungus gnats suggests multiple evolutions of the trait. This
concentration of bioluminescence may be due to the unusual, sedentary nature of prey
capture (i.e., use of webs) that allows the "mimicry" of a stationary abiotic light cue,
or the atypically potent defenses webs and associated chemicals might provide (i.e.,
an aposematic display of unpalatability).

Key Words: Mycetophyllidae, Orfelia, fungi, prey-attraction, aposematism

















Behavioral Ecology Symposium '97: Siuinski 283

RESUME

Muchos artr6podos se mueven hacia o lejos de una fuente de luz. Larvas de ciertos
moscos micetofilidos luminiscentes aprovechan este comportamiento para obtener
sus press. Estos moscos produce redes con una mucosidad, en ocasiones adornadas
con gotitas venenosas, para atrapar a una variedad de artr6podos pequenos. Es posi-
ble que al mismo tiempo las luces los protejan de sus depredadores fototr6picos nega-
tivos y/o que las usen como senales aposematicas. Por otra parte, las luces pueden
ayudar a himen6pteros parasitoides a localizar a los moscos micetofilidos. La luminis-
cencia de los hongos puede atraer a dipteros pequenos, pudiendo haber evolucionado
para facilitar la dispersion mecanica de sus esporas. Entre los dipteros, la bioluminis-
cencia s6lo se encuentra en los Mycetophilidae, pero la variedad de 6rganos luminis-
centes que existe en esta familiar de moscos sugiere una evolucion multiple de esta
caracteristica. Esta concentraci6n de bioluminiscencia quiza se deba a la forma, fuera
de lo comun, sedentaria de la capture de la press (por ejemplo, el uso de redes) que
permit el "mimetismo" de una seal luminiscente abi6tica estacionaria, o a las atipi-
camente potentes defenses que sus redes y los products quimicos asociados pueden
proveer (por ejemplo, una exhibici6n aposematica de ser desabridos).





Much of life, including flies, moves toward or away from light, an attribute that has
interested both scientists and poets ("Ah sun-flower! Weary of time, /Who contest the
steps of the sun," William Blake). In general, the mechanics of orientation to light
have attracted more study than their functions; the functions often seeming self-evi-
dent. Mast (1911) provided an early list of plausible reasons for phototropisms, and
included examples drawn from the Diptera: "Negative responses to light tends to keep
these creatures (fly larvae) buried in the cadavers where they find food.... When ...
a bee in a flower or a pomace fly in a wormhole of a decaying apple is excited it flies
directly to the light and ordinarily escapes."
In addition to simply moving towards shelter and darkness or freedom and light,
arthropods also use light sources to navigate toward specific locations (the "light-com-
pass reaction"). Bees use relative sun position to communicate food locations to their
sisters (e.g., von Frisch 1967). Ants navigate with the aid of the sun in order to return
along a "bee-line" to their nests (Santschi 1911). By keeping a constant angle to the
sun (or to a pattern of polarized light in the sky generated by the sun) and taking into
account the passage of time, certain ants can steer a straight course across even such
complex and changing terrains as windswept desert sand. More interesting to the
nocturnal student of bioluminescence, the moon is the light source used by at least
two genera of navigating ants (Santschi 1923, Jander 1957). A beach dwelling amphi-
pod, Talitrus saltator (Montague), also uses the moon, in this case to determine the di-
rection towards optimum habitats (Papi 1960). On moonless nights the large yellow
underwing moth, Noctua pronuba L., uses stars about 95 degrees from Polaris for
navigation (Sotthibandhu & Baker 1979). When such an insect "... starts to fly across
an area of'unsuitable' habitat as part of a search for 'suitable' habitat it orients in it's
individual-specific preferred compass direction." By avoiding 'wandering' it can cover
the greatest possible territory with the least expense of time and energy (see also
Baker 1978).
There can be dangerous consequences to positive phototropism and celestial nav-
igation. A light, man-made or bioluminescent, can be mistaken for the greater illumi-
nation in a more open habitat. When a navigating insect confuses a small, nearby
light source for a heavenly one, an attempt to keep the light at a constant angle rela-

















Florida Entomologist 81(3) September, 1998


tive to the body results in a spiraling flight into the source (e.g., Frankel & Gunn
1967). Flies can be both the victims and the beneficiaries of these mistakes.

BIOLUMINESCENT ADAPTATIONS IN FLIES

Luminous flies and prey attraction: Whatever the reasons for the orientation and
movement of insects towards light, some bioluminescent Diptera have exploited the
behavior for their own ends. All are fungus gnats (Mycetophilidae: Keroplatinae);
Nematocera with vermiform larvae that resemble small crane flies as adults (Fig. la,
d). Just a dozen or so of the more than 3000 species in the family are luminous, always
as larvae, and often as pupae and adults; e.g., only the egg-stage of the New Zealand
species Arachnocampa luminosa (Skuse) is nonluminous (Richards 1960), but adults
and young larvae of the Swedish Keroplatus sesiodes Wahlerg bear no lights (Harvey
1952).
Most luminescent fungus gnats are poorly studied and some specimens remain of-
ficially undescribed. The latter include a single larva found on a New Guinea rain for-
est floor (Bassot & Hanson 1969, Lloyd 1978), an assembly of larvae once observed on
the ceiling of a Nicaraguan cave (Gissele Mora, pers. comm.), a suspected new form of
Arachnocampa collected in Fiji (Harvey 1952), and a spelunker's report of luminous
"glow-worms" in an unidentified gypsum cave in the southwestern United States
(Davis 1966: for a discussion of light organ placement and morphology see the section
"Conclusion: the distribution of bioluminescence in flies").
The majority of mycetophilids develop in fleshy or woody fungi. Even those found
in dead wood, under bark, or in the nests of squirrels and birds are probably myce-
tophagous (Vockeroth 1981). However, the larvae of luminous species are typically
carnivorous. A possible exception to be addressed later is the Japanese Keroplatus
nipponicus Okada (Kato 1953; in addition, see feeding habits of the German species
K. testaceus Dalman [Pfeiffer & Stammer 1930, Stammer 1933]).
Luminescent species produce webs of mucous and silk. Web building is frequently
encountered in both luminous and nonluminous carnivorous fungus gnats, (e.g.,
Mansbridge & Buston 1933). The strands of the web are often scattered with adhesive
or poisonous droplets (i.e., the oxalic acid found in Platyura and Orfelia species). Gen-
erally, the larva has some sort of shelter associated with its web, either a connected
crevice or a mucous tube. It ventures out to subdue small arthropod prey with a ven-
omous oral secretion, and then retreats to the shelter with its meal. Larvae, acting in
a manner reminiscent of spiders, restrain insects larger than themselves with mu-
cous and later wrap them in silk. Rather than descend along the hanging strands of
their webs, the larvae of A. luminosa swallow the line and pull their prey toward
themselves (Richards 1960).
The forms of the webs vary substantially. That of Orfelia fultoni (Fisher) is a spray
of strands suspended in a flat plane over hollow places on the surface (Fulton 1941;
Fig. Ic). Spindle shaped deposits of adhesive anchor the side strands of the web, which
may measure up to 5 cm across. The web ofA. luminosa is suspended from the ceilings
of caves and hollows, and consists of a horizontal thread from which are hung multiple
"fishing lines" that can be more than 50 cm long in still, subterranean air, but are
much shorter in more exposed situations (Gatenby & Cotton 1960; Fig. Ib). The lines
are studded with adhesive droplets. A similar web is produced by a nonluminous spe-
cies of Orfelia, 0. aeropiscator Jackson, in the jungles and caves of Costa Rica (Jack-
son 1974), thus demonstrating that the very different plane-surface and suspended
fishing-line designs can be generated by species within a single genus (see a discus-
sion of the historical relationship of mycetophilid phylogeny and adaptation to salta-
tion in evolutionary theory in Gould 1986, Goldschmidt 1948).















Behavioral Ecology Symposium '97: Siuinski 285

The prey of luminous fungus gnats consists of small arthropods, some of which
presumably have been attracted by the predator's lights. Arachnocampa luminosa
glows more brightly when hungry (Richards 1960). Larvae of this species in New
Zealand's famous Waitomo Cave feed mainly on the chironomid midge, Anatopynia
debilis (Hutton), that breeds in the waters beneath the glow-worm colony (Richards
1960). In other locations trogophytic tipulids, moths, stone flies, caddis flies, sand
flies, red ants (apparently falling from the ceiling), spiders, millipedes, isopods, and
even small snails are also captured (Stringer 1957). Cannibalism is common. Fulton
(1941) found the remains of a cockroach and an ant in webs of 0. fultoni, but noted
that smaller insects were completely consumed and supposed that Collembola were
its normal fare.
Transparent and blackened petri dishes covered with an adhesive have been
placed over and near 0. fultoni larvae in order to a) substantiate the hypothesis that
larvae glow to attract prey and, b) to sample the insects attracted (Sivinski 1982). Col-
lembola were commonly collected in both dark and illuminated traps, but only small
Diptera, particularly cecidomyids and phorids, were significantly more numerous in
traps baited with larval lights. The attraction of flying (i.e., mobile), but not of nonfly-
ing (i.e., relatively sedentary) arthropods, is consistent with the phototropic behaviors
of the victims serving as a means of orientation during travel.





-Jp



'- i i t
i I ;








3 "'N





Fig. 1. a-The vermiform larva ofArachnocampa luminosa bears a single light or-
gan on the terminal segment. Other species have lights on the head and tail (Orphelia
fultoni), or glow along most of their bodies (e.g., Keroplatus spp.). b-Mycetophilids
use various forms of webs to capture prey. InArachnocampa luminosa, "fishing lines"
are suspended from a major horizontal line connected to a larval retreat. c-The web
of Orphelia fultoni is a flat spray of lines, typically spread over fissures in mossy soil.
The lines are anchored to the substrate by adhesive droplets. d-An adult male of Or-
phelia fultoni.

















Florida Entomologist 81(3) September, 1998


The colors of mycetophilid luminescence differ from the usual greens and yellows
of other insect lights (Sivinski 1981a). Keroplatus sesiodes and japonicus larvae emit
a bluish-white light (Wahlberg 1849). Orphelia fultoni larvae, locally abundant in the
damp ravines of the southern Appalachian Mountains where they are known as "dis-
mal-lights," produce a vivid blue luminescence (Fulton 1939). Arachnocampa lumi-
nosa glows blue-green, with a peak emission at 487 nm (Shimura et al. 1966). Adult
males, who seek out luminous female pupae and adults, have a corresponding peak in
their visual sensitivity (Meyer-Rochow & Eguchi 1984; see section on luminous sexual
signals). These unusual colors might contribute to prey attraction. Insect eyes tend to
be more sensitive to the short wavelength colors, and Tyndall scattering may give a
bluish cast to the celestially lite night sky, (unnoticed by human observers except
"once in a blue moon"). If so, insect prey might perceive attractive, open, areas in fo-
liage as being blueish.
Luminescence as a defense against predators: In addition to luring prey, biolumi-
nescence may serve other roles. For instance, one Japanese fungus gnat, K. nipponi-
cus, is both luminous and a web builder, yet it appears to eat only fungal spores (Kato
1953). Presumably, its light performs a function other than prey attraction, perhaps
repelling negatively phototropic enemies (see Sivinski & Forrest 1983), or serving as
an aposematic signal.
Mycetophilid larvae may not be defenseless. A web festooned with poisons and ad-
hesives might alert a resident of a predator's approach or restrain it from reaching the
larva. Fulton (1939) noted that webs woven by gregarious and nonluminous fungus
gnats in decaying wood seemed to serve chiefly to block predatory or parasitic enemies
(the luminous K. sesiodes is also gregarious, living in groups under a common gluti-
nous web on the lower surface of mushrooms [Wahlberg 1848]; see also K. tipuloides
Bosc [Santini 1982]). Cave wetas (Rhapdidophorids) in New Zealand caverns avoid
the webs ofA. luminosa, which tangle in their legs and antennae (Richards 1960). One
unfortunate weta placed among webs remained corralled without food for sixteen
days. A number of mycetophilid pupae are luminous (e.g., Gattenby & Cotton 1960,
Sivinski 1982), and while these are unlikely to be engaged in prey attraction they
might be emitting a warning signal. Attraction of food with light could be a second-
arily evolved elaboration of what was initially an aposematic display and a fortress.
The luminescence of a number of fungus gnats, larvae and pupae, changes follow-
ing disturbance (e.g., Gatenby 1959). This is consistent with lights repelling/startling
negatively phototropic intruders, or acting as a warning signal. Keroplatus testaceus
larvae brighten their lights when stimulated (Wahlberg 1849), although the glow ofK.
nipponicus remains constant despite "pressing, puncturing, and cutting" (Haneda
1957). Orfelia fultoni also continues to glow while its' container is handled (Fulton
1941). Tapping on the vial containing the unidentified New Guinean specimen in-
creased the frequency of it's light emissions, but not its' intensity (Bassot & Hanson
1969). On the other hand, disturbances cause A. luminosa larvae to "gleam very bril-
liantly" for a brief time and then douse their lights (Hudson 1886, Gatenby & Ganguly
1956).
Miscellaneous luminous social signals: Manipulation of the phototropic responses
of arthropods, including flies, is presumably responsible for the evolution of lights in
mycetophilids. However, once evolved, lights could be used as displays in aggressive
and sexual interactions.
i-Luminescence in larval conflicts: Light may communicate size and strength
among conspecific larvae. NeighboringA. luminosa larvae commonly fight, the loser
sometimes being eaten; "While fighting continues, each larva glows brilliantly, and it
is comparatively easy to pick out a pair of fighting larvae in the darkness because of
the intensity of the color and the brightness of their lights" (Richards 1960).

















Behavioral Ecology Symposium '97: Siuinski 287

ii-Luminous sexual signals: Males of certain mycetophilid species orient towards
adult-female and pupal lights to locate mates. While male pupae ofA. luminosa are
luminous (Gatenby & Cotton 1960), those of nearly mature females are particularly
bright and likely to glow in response to touch (Richards 1960). An adult male landing
upon a female pupa will cause it to luminesce. Males (up to 3 at a time) cling to such
pupae, fighting to dislodge competitors and waiting for the female to eclose. If no male
is attached at the time of eclosion, adult females employ light to ". . attract a male
fly, flashing it on and off till one arrived." Females usually lose their luminescence
with the commencement of oviposition, though males continue to glow throughout
their lives. The function of their continued luminescence is mysterious. Lloyd (1978)
discusses the sexual selection ofA. luminosa's luminescent signaling system, and sug-
gests that females, both as pupae and adults, may attempt to attract multiple suitors
before copulating. The resulting competition among the males might result in insem-
inations by particularly fit mates. 0. fultoni pupae are luminescent and adult males
have been captured in traps baited with glowing larvae (Sivinski 1982). These larval
lights may resemble luminous pupae to searching males.

THE DANGERS OF BIOLUMINESCENCE AND FUNGAL EXPLOITATION OF PHOTOTROPISM
IN FLIES
Fly luminescence attracting predators and parasitoids: Luminous mycetophilids are
attacked by hymenopterous parasitoids. An ichnuemonid, Eusterinx (= Dalloterrea) sp.
emerged from a larva of 0. fultoni (Fulton 1941), and a diapriid, Betyla fulva Cameron,
was reared from the pupae ofA. luminosa (Marshall 1882). Small unidentified Hy-
menoptera were most abundant in traps where 0. fultoni's larval lights were used as
bait (Sivinski 1982). Two species of phalangids prey on the larvae of A. luminosa (Rich-
ards 1960). All 4 of the phalangids trapped in an 0. fultoni habitat occurred in the -1/
4 of the traps where larval lights were visible, as did 10 of 18 spiders (Sivinski 1982).
Luminescent bacteria infect Diptera and other arthropods. For example, lumi-
nous, diseased chironomid midges have been observed across Europe, and in the New
World, mosquito pupae in Brazilian epiphytes sometimes have glowing purple
patches on their cuticles (cit. in Harvey 1952). Many infections appear to be benign,
although some are fatal to their hosts. It is possible that bacterial lights attract new
hosts, alternative hosts (e.g., fish) or agents of dispersal (Hastings 1978). For example,
after entering an insect, one entomopathogenic nematode releases luminescent bac-
terial symbionts into the hemocoel. The microbes first kill the victim, and then lumi-
nesce (Nealson 1991). The light attracts other nematodes, which presumably carry
the bacteria to another insect.
From a different perspective, nonluminous dipteran predators and parasitoids
might locate luminous nondipteran prey by their lights. Adult North American fire-
flies (Lampyridae) of several genera are attacked by the parasitic phorid flyApoceph-
alus antennatus Malloch (Lloyd 1973), and to a lesser extent by a tachinid,
Hyalomyodes triangulifer (Loew) (Sabrosky & Braun 1970, Lewis & Monchamp
1994). It is not known if the flies exploit bioluminescence to hunt down their hosts.
However, host beetles occur in both luminescent and nonluminous genera (Brown
1994), and male and female Photinus marginellus LeConte, whose light displays dif-
fer considerably in frequency and duration, have similar rates of parasitism (Lewis
and Monchamp 1994).
Luminous fungi and the exploitation of flies: A relationship based on positive pho-
totropism may exist between luminous mushrooms and certain flies. Some fungi emit
light. Luminescence can be present in mycelia (e. g., a number of Mycena species, Was-
sink 1978) or in both the mycelia and the fruiting body (e. g., North American popu-
lations ofPanellus stypticus (Bull. Ex Fr.) Karst. (Cf. Singer), Buller 1924). Mushroom

















Florida Entomologist 81(3) September, 1998


(fruiting body) lights have been described as blue, white, or green depending on the
species (Buller 1924, Wassink 1979). Emission intensities vary considerably. In the
forests of Borneo Mycena manipularis (Berk.) Metrod are visible at 40 meters (Zahl
1971). One Australian species "pours forth it's emerald green light" with sufficient in-
tensity to read by (Lauterer 1900 in Buller 1924). An American journalist wrote his
wife from a World War II battle field in New Guinea; "I'm writing to you tonight by the
light of five mushrooms." (Zahl 1965). Others, such as the common Floridian species
Dictyopannus pusillus (Lev.), are dimmer and the eye often requires several minutes
of dark adaptation before their glows can be perceived.
There have been a number of speculations on the function (if any) of fungal biolu-
minescence. For example, it has been suggested that the lights of mushrooms repel
negatively phototropic fungivores, attract arthropods that then excrete in the vicinity
of the fungus and so nurture it, and act as an aposematic display of distastefulness (at
least one luminous species, the Japanese Pleurotis japonicus Kawam, is a common
cause of human poisoning; cit. in Sivinski 198 Ib).
Perhaps the oldest of these hypotheses is that the lights attract spore-dispersers,
i.e., insects that either contact and mechanically distribute spores, or feed upon and
then defecate spores (Ewart 1906). The odor and colors of nonluminous stinkhorn fungi
(Phallales) serve this role (e.g., Ramsbottom 1953). What rewards, similar to the
stinkhorn's odoriferous, spore-laden "gleba," that luminous fungi might provide are un-
known. If insects bear spores, it may be that they are simply manipulated by lights into
contacting spore-bearing surfaces. Certain insects, particularly Collembola and small
Diptera such as Phoridae, are more likely to be captured in glass traps baited with live,
glowing D. pusillus than in traps containing freshly killed and dark specimens (Sivin-
ski 198 b). Increased interactions with insects diminishes the plausibility of the argu-
ment that luminescence is a functionless, and by implication consequence less, by-
product of metabolism and is consistent with the attraction of spore dispersers.
The topography and timing of lights in fruiting bodies are suggestive of guiding
dispersers. In Mycena pruinosa-visida Corner and M. rorida (Fr.) Quel. from the Far
Eastern tropics only the spores glow (Haneda 1955). Most fruiting body lights are re-
stricted to, or brightest, in the spore-bearing hymenium, i.e., "gills" (Wassink 1979),
and P. stypticus glows most strongly at the time of spore maturation (Buller 1924). In-
terestingly, a number of fungal mycelia have a daily luminous rhythm, with minima
around 9 o'clock in the morning and maxima around 9 o'clock at night (Berliner
196 la,b). Although spore dispersal is unlikely to be the function of these lights, their
increased intensity during times when they can be best perceived suggests they play
some communicative role in the biology of their emitters.

CONCLUSION: THE DISTRIBUTION OF LUMINESCENCE IN FLIES

E. Newton Harvey, a giant in the study ofbioluminescence, regarded the phyletic
distribution of living light as its most puzzling aspect. He noted that while the num-
ber of luminous species is "vanishingly small," their diversity is surprisingly great;
"..., as if a handful of damp sand has been cast over the names of various groups writ-
ten on a blackboard, with luminous species appearing wherever a mass of sand
struck." (1952). In the Diptera the "sand" only struck the Mycetophilidae.
The distribution of bioluminescence among flies presents a similar peculiar pat-
tern. While luminescence is unique to single subfamily of fungus gnats, there is an ex-
traordinary variety of light organ morphologies within the taxon. Lights are present
in the anterior 5 segments and the small posterior segment of 0. fultoni larvae, and
consist of binucleate-giant-black, secretary cells (Bassot 1978). Species of Keroplatus
tend to be luminous throughout their bodies, as was an unidentified New Guinean

















Behavioral Ecology Symposium '97: Siuinski 289

larva whose glows traveled in waves along it's length (J. M. Bassot & F. E. Hanson
1969). In Keroplatus larvae the light originates from fat cells found around the gut
(Kato 1953, Baccetti et al. 1987). The source of light in the New Guinean insect is un-
known, although giant black cells were not present in the specimen (Bassot & Hanson
1969). The single light organ on the terminal segment of the abdomen of A. luminosa
consists of modified Malpighian tube tissue and includes a concave mat of tracheoles
on its' ventral side that acts as a reflector (Wheeler & Williams 1915). The various
morphologies of fungus gnat light organs suggest several independent evolutions of
bioluminescence within the family.
Why among flies did selection favor lights only in mycetophilids, but then so often?
First, the step from nonluminescence to luminescence may not be particularly com-
plicated, hence the potential for evolution to produce the great variety of luminous
species (and fungus gnat light organs). In addition to the luminous Mycetophilidae,
there are numerous instances of bioluminescent arthropods isolated from a phyletic
history of bioluminescence; i.e., luminescence arising without sharing the genetic her-
itage of a recent luminous ancestor. For example, luminescent species of millipedes oc-
cur in only 2 genera, one Asian and the other restricted to certain mountain valleys
in California (Haneda 1955, Causey & Tiemann 1969; see an odd case of luminous-
milliped phobia in Yuswasdi [1950]). In the Coleoptera, hundreds of luminous species
occur in families rich in bioluminescence such as the Lampyridae and Phengodidae.
Yet only a single throcid (i.e., trixagid) species, Balgus schnusei Heller from French
Guiana, is known to be luminescent. It emits green light from 2 swollen spots on the
prothorax (Costa 1984; note that the Throcidae are related to the Elateridae, which
contains a number of luminous species with similar prothorasic light organs [e.g.,
Lloyd 1978]). More surprising is the recent discovery of a luminous staphylinid! Costa
et al. (1986) collected larvae of a Brazilian Xantholinus sp. with a light organ in the
8th abdominal segment. This is the only known case of luminescence in the entire Sta-
phyliniformia, a clade of 28 families.
If bioluminescence can arise without extensive "preadaptation," why is it so rare or
absent in many taxa? Or to turn the question around, what unusual set of circum-
stances favor its evolution in the fungus gnats, and not in other Diptera? Carnivorous
mycetophilids are peculiar in that the larvae are nocturnal predators that employ
webs to capture prey. Perhaps, such a stationary nature is both a requirement for dup-
ing phototropic victims and rarely encountered in flies (the pit-trap digging larvae of
Vermilionidae are stationary, but underground and not visible to potential prey, e.g.,
Wheeler 1930). A slightly facetious critic of this argument might wonder why there
are no bioluminescent spiders (although Brown 1925, 1926 reports a luminous spider
in Myanmar [Burma] that glowed more brightly "when approached or shaken"). Al-
ternatively, perhaps webs and their associated chemicals are one of the few potent de-
fenses raised by relatively exposed dipteran larvae. If so, fungus gnat larvae may
have rare opportunities to advertise their unpalatability to predators with light.

ACKNOWLEDGMENTS
James Lloyd, Sid Mayer, and Steve Wing suggested many important improve-
ments to the manuscript. Jennifer Sivinski helped collect mushrooms, and Kevina
Vulinec produced the excellent illustration.

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Florida Entomologist 81(3)


September, 1998


BIOLOGY AND BEHAVIOR OF PSEUDACTEON
DECAPITATING FLIES (DIPTERA: PHORIDAE) THAT
PARASITIZE SOLENOPSIS FIRE ANTS (HYMENOPTERA:
FORMICIDAE)

SANFORD D. PORTER
USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology
P.O. Box 14565, Gainesville, FL 32604

ABSTRACT

Larvae of phorid flies in the genus Pseudacteon have the unusual habit of decapi-
tating fire ant workers and pupating inside the empty head capsule which they use as
a pupal case. Flies in this genus are the subject of considerable interest because they
have the potential of being used as classical biological control agents against imported
fire ants in North America. This paper details what is known and not known about
their interesting life history, attack behavior, mating behavior, host specificity, and
impacts on fire ant behavior. The biogeography, community structure, and possible
impacts on fire ant populations are also considered.

Key Words: biological control, classical biocontrol, parasitoid, larvae, pupae, host
specificity

RESUME

Moscas forideas do genero Pseudacteon produzem larvas que apresentam um ha-
bito nao usual de decapitar as formigas operarias e pupas dentro da capsula cefalica
vazia, a qual elas utilizam como camara pupal. Estas moscas sao asunto de conside-
ravel interesse porque elas tem potential de serem utilizadas como agents de con-
trole biol6gico classic contra as formigas lava-p6 importadas na America do Norte.
Este trabalho detalha o que 6 conhecido e desconhecido sobre seu ciclo de vida, com-












Behavioral Ecology Symposium '97: Porter


portamento de ataque, comportamento de reproducao, especificidade hospedeira e im-
pactos do comportamento da formiga lava-p6. A biogeografia, a estrutura comunitaria
e os possiveis impacts sobre as populacoes da formiga lava-p6 sao tamb6m relatadas.



Phorid flies in the genus Pseudacteon (Coquillett 1907) and several related genera
(Pergande 1901) produce larvae that decapitate worker ants and pupate inside their
empty heads. Not surprisingly, these miniature flies (Fig. 1) are about the size of the
heads of their hosts. The attack behavior of Pseudacteon flies was first described in de-
tail by Wasmann (1918) in Holland, Borgmeier (1922) in Brazil, and Smith (1928) in


7/


9


I,


Fig. 1. Lateral view of female Pseudacteon nocens. Length is about 1.4 mm.
















Florida Entomologist 81(3) September, 1998


the United States. Over a period of 50 years, Borgmeier gradually named most of the
known species in this genus (Borgmeier 1925, 1962, 1963, Borgmeier & Prado 1975).
The possibility of using these flies as fire ant biocontrol agents lead Williams (1980)
to make extensive collections and observations in Brazil. Feener and Brown (1992) re-
ported that Pseudacteon flies disrupted foraging of native fire ants in Central America
and proposed that flies from South America might make good biocontrol agents for im-
ported fire ants in the United States. Orr et al. (1995) and Porter et al. (1995c) docu-
mented substantial impacts of Pseudacteon flies on fire ant foraging in South
America. The unusual life history of immature Pseudacteon flies was first described
by Pesquero et al. (1995) and Porter et al. (1995b). Research groups at the University
of Texas (Gilbert 1996) and the USDA-ARS laboratory in Gainesville, Florida are cur-
rently examining the potential use of Pseudacteon flies for classical biocontrol of im-
ported fire ants in the United States.

LIFE HISTORY

The life cycle for Pseudacteon flies begins when a torpedo-shaped egg (Fig. 2A;
Wasmann 1918) is injected into the body of a worker ant. The duration and morphol-
ogy of the first instar is unknown, but the second instar is found in the ant's head by
day four (Fig. 2B; Porter et al. 1995b). During this instar and most of the third instar
(Fig. 2C), the maggot apparently relies on ant hemolymph for nutrition, because little










1 0.2











Fig. 2. Developmental stages of Pseudacteon litoralis. A) Egg, B) Second instar, C)




Third instar. Note the two anterior spiracles projecting laterally behind the head re-
gion and the two paired posterior spiracles. D) Puparium inside head capsule of fire
ant worker. The head capsule is shown in ventral view with the sclerotized cap of the
fly puparium filling the mouth opening of its host. The remainder of the puparium is
indicated by a dotted outline. Two respiratory horns extend diagonally out of the ant
head capsule. (modified from Porter et al. 1995b)
Fig. 2. Developmental stages ofPseudacteon litoralis. A) Egg, B) Second instar, C)
Third instar. Note the two anterior spiracles projecting laterally behind the head re-
gion and the two paired posterior spiracles. D) Puparium inside head capsule of fire
ant worker. The head capsule is shown in ventral view with the sclerotized cap of the
fly puparium filling the mouth opening of its host. The remainder of the puparium is
indicated by a dotted outline. Two respiratory horns extend diagonally out of the ant
head capsule. (modified from Porter et al. 1995b)

















Behavioral Ecology Symposium '97: Porter


if any tissue is consumed. Parasitized ant workers appear normal and healthy until
a few hours before the maggot is ready to pupariate. It is not yet known what effects
developing larvae may have on the behavior of their hosts; however, suppressing for-
aging would extend the longevity of their host (Mirenda & Vinson 1981, Porter & Jor-
gensen 1981) thus giving the larvae a better chance to complete development.
The decapitation process begins when parasitized workers crumple on their sides
unable to walk (Fig. 3.1). The third instar maggot seems to release an enzyme or hor-
mone that causes the intercuticular membranes of its host to degenerate (Porter et al.
1995b). This process usually loosens the head and first pair of legs; sometimes the
other legs and gaster are also affected. The maggot then proceeds to consume the en-
tire contents of the ant head, a 6-12 h process that usually results in decapitation of
its living host (Fig. 3.2). The legs and sting of the headless body are often still twitch-
ing. In laboratory colonies, most decapitated and dying workers are rapidly carried
out of the nest chambers onto the refuse pile. Using a series of hydraulic extensions
(Fig. 4A), the maggot then pushes the ant's mandibles and tongue apparatus aside
(Fig. 3.3). Eventually the maggot maneuvers itself under the tentorial arms inside the
head capsule (Fig. 5). The first three segments then compress and harden to form a
distinctive plate that precisely fills the oral cavity (Fig. 2D, Fig. 3.4). The remainder
of the puparium remains unsclerotized and is protected by the ant head capsule (Fig.
5). Three to four days later, during actual pupation, two whisker-like respiratory
horns emerge diagonally out of the puparium, positioned so that they extend out of
the corners of the oral cavity of their host's head capsule (Fig. 2D and 5; Porter et al.
1997). This unusual type of puparium is shared by all 10 of the Pseudacteon species
that have been reared to this stage (Porter et al. 1995b, Morrison et al. 1997, Porter
et al. 1997; unpublished data).
The fate ofPseudacteon puparia in the field is not known, but based on laboratory
observations, puparia are probably initially deposited with dead fire ant workers in
refuse piles on the surface of the ground (Howard & Tschinkel 1976). Eventually the
puparia are probably scattered by rain, wind and/or other species of scavenging ants.
Pupal development requires 2-6 weeks, depending on temperature (Morrison et al.



















Fig. 3. Four stages in the decapitation of fire ant workers parasitized by Pseudac-
teon flies. 1) Crippled worker with degenerating intersegmental membranes and re-
laxed mandibles. 2) Decapitated worker with maggot consuming tissues in the head.
3) Ant head with mandibles and tongue apparatus pushed aside in preparation for pu-
pariation. 4) Decapitated worker with fly puparium inside head.
















Florida Entomologist 81(3)


September, 1998


A

Fig. 4. A) Maggot pushing away ant mouth parts with a series of hydraulic exten-
sions just prior to pupariation. B) Adult male fly in the process of emerging from pu-
parium.


1997, Porter et al. 1997; unpublished data). The total developmental period from egg
to adult is 5-12 weeks, again depending on temperature.
Emergence of adult flies generally requires only a few seconds (Fig. 4B). The scle-
rotized cap pops open and the adult fly slips out of the ant head capsule. Emergence
only occurs in the first few hours after sunrise (Porter et al. 1997), as is the case for
many kinds of flies. Newly emerged flies are ready to mate and lay new eggs within
several hours of eclosion. Adult Pseudacteon flies are 0.9-1.5 mm in length (Borgmeier
& Prado 1975), depending on the sex and species of fly. Adult flies can live 3-7 days in


Fig. 5. Two Pseudacteon puparia removed from ant head capsules (dorsal and ven-
tral views) together with puparium still in ant head capsule. Note the large white un-
sclerotized portion of the puparium that is normally protected by the head capsule of
its host. a) Left anterior larval spiracle (compare Fig. 2c), b) Posterior larval spiracles
(compare Fig. 2c), c) Pupal respiratory horns, d) Tentorial arms of ant extending diag-
onally across dorsum of fly puparium. Bar indicates 0.5 mm.















Behavioral Ecology Symposium '97: Porter


the laboratory if they are relatively inactive (Pesquero et al. 1995, Gilbert 1996, Por-
ter et al. 1997). However, the life span of flies that are attacking ants is probably much
shorter (Porter et al. 1997). Virtually nothing is known about what adult flies do or
where they spend their time when they are not attacking fire ants. Adults will stop
and drink water or lap up sugary substances if they contact them, but they do not ap-
pear to be attracted to them. Pseudacteon flies are not attracted to various kinds of
fruits, flowers, human food products, or human feces (Porter et al. 1997; unpublished
data). They are also not attracted to people. Data from Austin, TX indicates that adult
flies commonly disperse several hundred meters from host colonies (Morrison et al.
unpublished manuscript, University of Texas at Austin).
Interestingly, the sex of most Pseudacteon species seems to be facultatively deter-
mined by the size of the host (Fig. 6; Porter et al. 1997, Morrison et al. in press). This
is probably because fire ant workers are highly variable in size (2-6 mm in length) and
female flies are more fit if they emerge from larger hosts. The exact mechanisms of sex
determination in Pseudacteon flies is unknown. Maternal sex determination via hap-
lodiploidy occurs in many parasitic hymenoptera, but haplodiploidy is not known to
occur in the family Phoridae or other related families of flies. Karyotypes should help
resolve this question, as would transferring developing eggs or larvae from small
hosts to large hosts and vice versa.

ATTACK BEHAVIOR

Female Pseudacteon flies hover 3-5 mm above their hosts while orienting for an at-
tack (Fig. 7; Borgmeier 1922, Smith 1928, Williams 1980, Porter et al. 1995c). Once
properly aligned, they dive in and inject an egg into the thorax of a worker ant using
a hypodermic-shaped internal ovipositor (Wasmann 1918, Zacaro & Porter unpub-
lished data). Each species of fly parasitizes a characteristic size range of ants (Morri-


.O *


Female


Male


Fig. 6. Sex in most Pseudacteon flies appears to be determined by the size of their
host. Female flies generally emerge from host head capsules that are distinctly larger
than males. With Pseudacteon tricuspis, the lower quartile of female-producing head
capsules overlaps with the upper quartile of male-producing head capsules. The width
of head capsules ranges from about 1.3 mm (left) to 0.7 mm (right).
















Florida Entomologist 81(3)


September, 1998


r I










Fig. 7. Female Pseudacteon flies generally hover a few millimeters above their
hosts prior to diving in and rapidly injecting an egg into the thorax.


son et al. 1997). This size range is usually consistent even across different ant species
and colonies having different size ranges of workers (Morrison et al. in press, Morri-
son and Gilbert 1998). Male and female alates in the ant colony are ignored by most
flies (Smith 1928, Williams & Banks 1987) and are never successfully parasitized (un-
published data). Egg laying bouts for Pseudacteon tricuspis Borgmeier and Pseudac-
teon litoralis Borgmeier generally last about an hour, during which time they attempt
to oviposit 30-120 times (Morrison et al. 1997). Oviposition attempts result in para-
sitism 8-35% of the time depending on the species of fly and conditions (Porter et al.
1995b, Gilbert & Morrison 1997, Morrison et al. 1997, Porter et al. 1997). Female flies
have 100-200 mature eggs in their ovaries upon emergence (Zacaro & Porter unpub-
lished data).
Oviposition strikes are fast to very fast, requiring only 0.1-1.0 sec depending on
the species (Borgmeier 1922, Porter et al. 1995a, unpublished observations). Each
species of fly has a distinctively shaped external ovipositor (Fig. 8) which is presum-
ably used in a lock-and-key fashion to align the internal ovipositor with a particular
part of the host's body. The form of the external ovipositor varies greatly from species
to species suggesting that each is used quite differently (Feener 1987). Unfortunately,
the small size of the fly and the rapid speed of the attack has so far precluded any
studies concerning the relationship between ovipositor form and function. The exact
sites for egg injection are also not known, but the coxal region seems likely for most
species.
Workers frequently appear stunned after an oviposition strike and often stilt up on
their legs (Fig. 9A) for a few seconds to a minute before running away. The flies are
generally too agile to be captured by fire ant workers; nevertheless, attacking fire ants
is a dangerous activity. Only about 30% of female flies survive after 4 h of attacks in
the laboratory (unpublished data). Many flies are apparently captured and killed
when they accidently fall into clusters of ants. Other flies simply appear to run out of
energy, stop flying, and are eventually chased down and killed by the ants.
How do flies locate fire ants? The answer is probably by cuing in on chemical odors
(Borgmeier 1922, Donisthorpe 1927). When fire ant mounds are disturbed in South
America, Pseudacteon flies usually begin appearing within 20 min if conditions are
appropriate. Presumably, they are able to detect fire ant odors over long distances. Ex-
















Behavioral Ecology Symposium '97: Porter


Fig. 8. Different species of Pseudacteon flies have very distinctive external ovipos-
itors which are apparently used in a lock-and-key fashion to position the hypodermic-
like internal ovipositor for injecting a single egg into their hosts. Pseudacteon affinis
(left), Pseudacteon tricuspis from Argentina (center), Pseudacteon borgmeieri (right).
Black bars indicate 50 pm.


actly how far is unknown; however, the fact that flies often require some time to ap-
pear suggests that they might be attracted from 10-20 m or more. However, studies of
fly dispersal around Austin, TX suggest that flies are attracted at distances of less
than 50 m (Morrison et al. unpublished manuscript). Chemical cues also seem impor-
tant in the short-range recognition (10-40 cm) of fire ant workers. In the field in Bra-
zil, several species of flies are capable of discriminating effectively and rapidly
between S. geminata and saevissima complex fire ants (Trager 1991) at distances of
40 cm or more, even though workers are almost certainly visually indistinguishable
at that distance (Porter et al. 1995a). It is not known whether long-range attraction
cues are the same as the short-range recognition cues, but it seems likely. At distances





















Fig. 9. A) After being attacked by decapitating flies, workers will often stilt up on
their legs and remain immobile for several seconds to a minute as if they are stunned.
B) When fire ant workers are being attacked, they often assume a stereotypical c-
shaped defense posture.

















Florida Entomologist 81(3) September, 1998


of less than 10 cm, visual cues are probably very important. Pseudacteon flies have
eyes with hundreds of ommatidia; presumably these afford them the necessary visual
acuity to track, orient and attack fire ant workers. Nevertheless, even at 10 cm, odor
cues appear to be necessary to initiate and maintain attack behavior (Porter & Alonso
unpublished manuscript). The flies might also be able to use contact odors to assess
the age and quality of fire ant workers. The source and nature of chemical cues are un-
known, but alarm pheromones, recruitment pheromones, cuticular hydrocarbons, and
aerosolized ant venom are all likely possibilities worth investigating (Orr et al. 1997).

MATING BEHAVIOR

In several Pseudacteon species (P. tricuspis, P.crawfordi Coquillett, and P. brown
Disney) both sexes are attracted to fire ants and mating occurs while females are look-
ing for workers to attack (Feener 1987, Feener & Brown 1992, Porter et al. 1997).
Males can usually be distinguished from females because they are slightly smaller
and because they do not track the movement of fire ant workers. Rather they hover in
the air spinning around looking for females. Mating in P. tricuspis is initiated in the
air when the male grabs hold of the female (Fig. 10). Copulation generally requires
only a fraction of a second during which time the pair fall briefly to the ground before
breaking up and flying away (Porter et al. 1997). Both sexes mate multiple times. The
sex ratios of P. tricuspis adults collected in the field are often highly male-biased (e.g.,
5:1, Pesquero et al. 1993; 2:1, Fowler et al. 1995, assuming all males were P. tricuspis).
Males of most other species of Pseudacteon flies are not attracted to fire ants and their
mating behaviors are currently unknown.

PSEUDACTEON BIOGEOGRAPHY

Pseudacteon flies have been collected in Europe, Asia, North America, and South
America (Disney 1994, Michailovskaya 1995). At least 18 species of Pseudacteon flies
have been found attacking Solenopsis fire ants in South America (Table 1). Another




















Fig. 10. Male Pseudacteon tricuspis approaching female to mate while the female
is searching for fire ant workers to attack. During mating, the pair generally fall to
the ground where they remain in copula a few tenths of a second before breaking up
and flying away. Black bar indicates 0.5 mm.


















Behavioral Ecology Symposium '97: Porter


TABLE 1. PSEUDACTEON FLIES THAT ATTACK FIRE ANTS IN NORTH AND SOUTH AMERICA.


Species' Known Range'

South America-saevissima complex ants


Ovipositor' Abundance2


P. borgmeieri
P. convexicauda
P. curvatus
P. solenopsidis
P. nudicornis
P. affinis
P. comatus
P. cultellatus
P. dentiger
P. lenkoi
P. litoralis
P. nocens
P. obtusus
P. pradei
P. near pradei
P. species A
P. tricuspis
P. wasmanni


South America
Brazil
South America
Brazil
South America
Brazil
Brazil
South America
Brazil
Brazil
South America
South America
South America
Brazil
Brazil
Brazil
South America
Brazil


Americas (Northern Hemisphere)-geminata complex ants


P. crawfordi
P. species B
P. longicauda
P. antiguensis
P. brown
P. grandis
P. spatulatus
P. arcuatus
P. bispinosus


U.S.A.
U.S.A.
Central America
Caribbean
U.S.A., Central Amer.
Caribbean
U.S.A.
Caribbean, Costa Rica
Honduras


'Determined from Borgmeler & Prado 1975, Disney 1991, Disney 1994, f
Pesquero and L. W. Morrlson, and B. V. Brown's "scrapbook".
Approximations from personal collecting efforts and (Williams 1980).


pecimens collected by and M. A.


eight species attack fire ants in North America, Central America, and northern South
America. Additional species will likely be discovered as collecting efforts are intensi-
fied and expanded into new areas. Also, several other species might need to be split if
distinctive populations are determined to be separate species. (e.g., Pseudacteon ob-
tusus Borgmeier and P. tricuspis). In contrast to the large number of Pseudacteon spe-
cies that attack fire ants, only seven species (Disney 1994) are known to attack other


unlobed
unlobed
unlobed
unlobed
bilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed
trilobed


uncommon
rare
common
local
uncommon
rare
rare
rare
rare
rare
very common
uncommon
common
common
rare
rare
very common
very common


unlobed
unlobed
unlobed
bilobed
bilobed
bilobed
bilobed
trilobed
trilobed

















Florida Entomologist 81(3) September, 1998


genera of ants in the New World (Crematogaster, Linepithema, Dorymyrmex, Liome-
topum, Neivamyrmex).
Most Pseudacteon species in South America are broadly distributed (Borgmeier &
Prado 1975; unpublished data) across a wide range of habitats and climates. For ex-
ample, P. litoralis, P. tricuspis, P. obtusus, and Pseudacteon curvatus Borgmeier have
all been collected from Sao Paulo, Brazil in the north to Cuiaba, Brazil in the west,
and south to Buenos Aires, Argentina. Even some of the less common Pseudacteon
species (e.g., P. borgmeieri, P. nudicornis Borgmeier, P. cultellatus Borgmeier, P. no-
cens Borgmeier) have been collected from Sao Paulo south to Buenos Aires. These
ranges encompass climates from tropical to temperate and habitats from tropical rain
forests and swamps to temperate rangelands and seasonally dry "cerrado" forests.
Several Pseudacteon species in North and Central America are also fairly widely dis-
tributed (Disney 1991).
Pseudacteon flies that attack fire ants appear to be associated with species in either
the saevissima or the geminata complexes (Table 1; Borgmeier & Prado 1975, Gilbert
& Morrison 1997, Porter 1998). Within both complexes, Pseudacteon species usually
attack several species of fire ants (Disney 1994, Porter et al. 1997). However, phorid
flies in South America have never been reported to attack the largest species of Sole-
nopsis fire ants: S. macdonaghi Santschi, S. megergates Trager, S. interrupta Santschi,
or S. quinquecuspis Forel. It will be interesting to determine whether these large fire
ants lack Pseudacteon parasitoids, share them with their slightly smaller but more
abundant relations (Solenopsis invicta Buren, S. saevissima, Solenopsis richteri
Forel), or have their own, as yet undiscovered, communities of Pseudacteon flies.
Little is known about physical factors that limit the distribution of Pseudacteon
species, but presumably there are thermal and moisture limits, as well as, limits as-
sociated with plant cover. Most decapitating flies do not seem restricted to specific
habitats or narrow vegetational types. The abundance of Pseudacteon flies at particu-
lar sites can be quite variable from month to month, or even from week to week. The
activity Pseudacteon flies around Austin, TX was limited by strong winds and stopped
when air temperatures fell below 20'C (Morrison et al. unpublished data). Fowler et
al. (1995) reported that Pseudacteon flies were active throughout the year in Rio Claro
near Sao Paulo, Brazil with peak populations occurring in the spring. Populations in
the fall can also be quite high (personal observations). There is no clear evidence for
diapause or discrete generations in these flies, although species in Austin, TX do not
appear to emerge during the winter months (Morrison et al. unpublished manuscript).


COMMUNITY STRUCTURE

In South America, 5-8 species of Pseudacteon flies are often found at the same site
(Porter et al. 1995a, Pesquero et al. 1996, Fowler 1997, Orr et al. 1997). At least three
behaviors help explain how so many closely related species partition niche space
while using the same host. First and perhaps most importantly, species in sympatric
communities attack different sizes of fire ant workers (Fig. 11A; Campiolo et al. 1994,
Fowler 1997, Morrison et al. 1997). When sympatric flies are viewed as a community,
almost all sizes of fire ant workers are subject to attack from one Pseudacteon species
or another (Morrison et al. 1997).
A second way that some phorid flies divide niche space is by selecting different pe-
riods of diurnal activity. In Brazil, P. litoralis is crepuscular, whereas the medium-sized
P. tricuspis is most active from late morning until late afternoon (Pesquero et al. 1996).
A third way sympatric Pseudacteon species limit competition is that they attack
fire ants engaged in different activities (Orr et al. 1997). For instance, some flies (i.e.,

















Behavioral Ecology Symposium '97: Porter


L.P
P. irnag. ]0M) B



M= 0. A B

..



0.4N 0.5 0.6 Bcfore During After
Phorid Thorax Width (mm) Phorid Attacks

Fig. 11. A) Different species of Pseudacteon flies attack different sizes of fire ant
workers. Often 5-8 species of flies occur at a single site. Taken together, species will at-
tack >90% of fire ant workers (from Morrison et al. 1997). B) In South America, fire
ant foraging generally terminates or is greatly reduced 2-3 minutes after decapitating
flies begin attacking foraging workers. (modified from Porter et al. 1995c).


Pseudacteon solenopsidis (Schmitz), P. borgmeieri, P. obtusus, P. nudicornis) appear to
specialize on fire ants along foraging trails (Orr et al. 1997) while other species appear
to specialize on ants at mound disturbances or during fire ant mating flights (Smith
1928, Williams 1980, Pesquero et al. 1993). Pseudacteon solenopsidis has the interest-
ing habit of chasing fire ant workers 10-20 cm off foraging trails before attacking them
(Borgmeier 1922, Orr et al. 1995, Orr et al. 1997). This mode of attack is time-consum-
ing; however, it may avoid shutting the foraging trail down (see below).


IMPACTS ON FIRE ANT BEHAVIOR

Fire ant workers are keenly aware of the presence of phorid flies (Borgmeier 1922).
A single attacking fly usually stops or greatly inhibits the foraging efforts of hundreds
of workers within 2-3 minutes (Fig. 11B; Feener & Brown 1992, Orr et al. 1995, Porter
et al. 1995c). Orr et al. (1997) reported that the degree of response was related to the
number of attacks. As soon as fire ant workers recognize the flies, they retreat into
exit holes or find cover. Other workers will curl into a stereotypical c-shaped defensive
posture (Fig. 9B; Feener & Brown 1992) that has only been reported when the ants
are under attack by phorids. The c-shaped posture seems to be more common among
S. geminata workers than saevissima complex workers (Feener & Brown 1992, Porter
et al. 1995a, 1995c). Foraging rates usually remain suppressed as long as the flies are
active and often for 15-60 minutes after the flies leave (Feener & Brown 1992, Porter
et al. 1995c).
The flies inhibit fire ant foraging as long as they are present, often for periods of
several hours (Orr et al. 1995). At any one time, phorid flies in South America can in-
hibit foraging at 10-20% of baits with fire ants (Porter et al. 1995c). Reduced foraging
appears to facilitate competition from ant species that might otherwise be excluded
from food sources in fire ant territories (Feener 1981, Orr et al. 1995). Several flies are
also sufficient to stop nest construction or "freeze" the activity of entire colonies in lab-
oratory nest trays (Fig. 12; Porter et al. 1995c). In Brazil, the "freezing" response var-
ies from colony to colony (Porter et al. 1995c). Some colonies always show strong

















Florida Entomologist 81(3) September, 1998


responses while others show little or no response. Strangely, this variability was not
related to collection location or species morphotypes.
The cessation of foraging, the c-shaped defense posture, and the freezing response
are all specific fire ant behavioral defenses against phorid flies. Another probable de-
fense is the foraging tunnel system (Disney 1994, Porter et al. 1995c). This system is
a series of tunnels 2-7 cm below the ground surface that radiate out from the mound
like branches on a tree (Markin et al. 1975). Even though a colony's territory may be
10 m across, foragers usually do not travel more than 0.5 m above ground from an exit
hole. It would be difficult for fire ants to maintain large territories and therefore large
colonies, if all foragers emerged from a central nest and traveled above ground for
many meters with phorid flies attacking them. The tunnel system also allows colonies
to shut down those portions of their territory under phorid attack while allowing them
to maintain activity in the remainder.
The cues that fire ants use to recognize phorid flies are unknown. The ants can ap-
parently see attacking flies and will clearly twist and turn to avoid their attacks. Ol-
factory and auditory cues might also be perceived by the ants at close range.
Observations in the field indicate that hovering male flies can suppress foraging
(Feener & Brown 1992, Porter et al. 1995c), but attacking females might be necessary
to initiate defensive responses (Orr et al. 1997). If this is true, then fire ants may be
releasing pheromones to trigger the group defensive responses.

HOST SPECIFICITY

All Pseudacteon flies are almost certainly parasitoids of ants. They have never
been reported to attack any other kind of organism, and virtually all phylogenetically
related phorid genera are also ant parasitoids (Brown 1993, Disney 1994). Their elab-
orate ovipositors and the adaptations of at least 11 species for pupation in the head
capsules of worker ants (Fig. 2D) further supports the conclusion that they are very
specialized parasitoids. Most Pseudacteon species are probably specific to ants in a
specific genus (Disney 1994). A possible exception is P. formicarum in Europe. Do-
nisthorpe (1927) reported that this fly attacks ants in several genera (Lasius, For-
mica, Myrmica, Tapinoma), but Wasmann (1918) held that it was probably specific to
ants in the genus Lasius. Hosts of this fly have never been verified by rearing tests.


















Fig. 12. A) If fire ants are unable to flee during attacks of decapitating flies, they
will often "freeze" and refuse to move even when prodded. B) Normal colony activity
with no flies present.

















Behavioral Ecology Symposium '97: Porter


The Pseudacteon species that attack fire ants appear to be specific to fire ants. Of
more than 20 New World species, only one unconfirmed report exists of a rare species
being collected over another genus of ants (Borgmeier 1962). Some Pseudacteon spe-
cies are apparently specific to individual fire ant species or species groups. For in-
stance, at least three species ofPseudacteon phorid flies attack native Solenopsis fire
ants in the U.S. (Table 1), but they have never been reported to attack imported fire
ants even when they clearly have had the opportunity (Morrison et al. 1997). The host
specificity of several parasitic Pseudacteon flies in South America was tested in the
field with 23 species of ants from 13 genera (Porter et al. 1995a). As expected, these
flies were attracted only to Solenopsis fire ants. A second field study showed that
Pseudacteon flies are specific to ants in the genus Solenopsis (Porter 1998). Further-
more, several series of no-choice tests conducted in quarantine showed, that four spe-
cies of Pseudacteon flies (P. litoralis, P. tricuspis, P. wasmanni (Schmitz), and P.
obtusus) readily attack imported fire ants, but they virtually do not attack native fire
ants (Gilbert & Morrison 1997, Porter & Alonso unpublished manuscript, Morrison &
Gilbert unpublished manuscript). A fourth species (P. curvatus) does attack both na-
tive and imported fire ants, although it still has not been reared to the adult stage in
native fire ants (Gilbert & Morrison 1997).


IMPACTS ON FIRE ANT POPULATIONS

The overall impact of phorid flies on fire ant populations is unknown; however, it
is clearly sufficient to have caused the evolution of a number of phorid-specific defen-
sive behaviors (Fig. 9B, 11B, and 12). These behaviors could only have evolved if Pseu-
dacteon flies had exerted population-level impacts on the survival of fire ant colonies
and/or their rates of sexual production (Porter et al. 1995c).
The introduction of exotic species usually occurs without natural enemies (DeBach
1974). This was certainly true for S. invicta. Over 30 natural enemies have been iden-
tified in South America (Williams 1980, Jouvenaz 1986, Porter et al. 1992) compared
to only four in the United States (Collins & Markin 1971, Jouvenaz et al. 1977, Neece
& Bartell 1981, Wojcik 1990, Kathirithamby & Johnston 1992, Williams et al. 1998).
The absence of natural enemies can allow exotic species to reach much higher pop-
ulation densities in newly invaded regions than in their native habitats (van den
Bosch et al. 1973, Huffaker & Messenger 1976). Not surprisingly, fire ant populations
in the United States are generally five times higher than in South America (Porter et
al. 1992, Porter et al. 1997). Imported fire ants are one of the most abundant insects
in the southeastern United States with average densities of 80-200 mounds/ha and
2,000-4,000 ants/m2 (Macom & Porter 1996). Escape from natural enemies is a likely
explanation for these unusually high densities, because analyses of factors such as cli-
mate, habitat, population structure, and cultural practices have not been useful in ex-
plaining intercontinental population differences (Porter et al. 1997).
Consequently, it is hoped that the introduction of phorid flies and other natural en-
emies from South America will be able to sufficiently tilt the ecological balance in the
United States so that our native ants can compete with the imported fire ant on an
"level playing field" (Fig. 13; Feener 1981, Feener & Brown 1992). If this happens, im-
ported fire ant populations in the United States could be reduced to levels similar to
those in South America. Phorid flies in North and Central America also have the pos-
sibility of being exported as biocontrol agents of exotic S. geminata populations in Af-
rica, India and the Pacific region.
Ants are among the most important of all terrestrial arthropod groups in terms of
both biomass and impacts on community structure (H6lldobler & Wilson 1990). Con-
















Florida Entomologist 81(3)


September, 1998


Fire
A BAis




N-tiv '
SAn Ai.,



-.4Lr';.o i ri-
..*.. ii ..........P&iiIi..i





Fig. 13. A) One likely explanation for the unusually high densities of fire ants in
the United States is that native ants are weighed down by their natural enemies
while imported fire ants have escaped almost all of their natural enemies. B) Import-
ing fire ant enemies that were left behind in South America may reestablish a more
natural ecological balance. If this happens, fire ants will loose their competitive ad-
vantage and populations should drop.


sequently, there has been considerable interest in the structure and diversity of ant
communities, most focused on competition among different species of ants (Wilson
1971). Relatively little, however, is known about the effects of pathogens and para-
sites on ant community structure (Feener 1981, Orr 1992, Briano et al. 1995, Orr et
al. 1995), perhaps because experimental manipulations at the community level are
usually very difficult or impossible to conduct. Fire ant biocontrol efforts offer a
unique opportunity to experimentally test the hypothesis that parasitoids, specifi-
cally phorid flies, are important in structuring the diversity and composition of ant
communities.

ACKNOWLEDGMENTS

L. R. Davis (USDA-ARS, Gainesville), L. W. Morrison (Univ. of Texas), D. H. Oi
(USDA-ARS, Gainesville), C. K. Porter (Gainesville, FL), J. M. Sivinski (USDA-ARS,
Gainesville), and C. T. Wuellner (Univ. of Texas) read the manuscript and provided nu-
merous helpful suggestions. Thanks are extended to B. V. Brown for sharing his Pseu-
dacteon scrapbook and taxonomic expertise. Thanks are also extended to J. A. Briano
(USDA-ARS, Buenos Aires, Argentina), H. G. Fowler (UNESP, Rio Claro, Brazil), L. A.
Nogueira de Sa (EMBRAPA, Jaguariuna, Brazil) and all the people at their labs that
provided logistical, linguistic, and technical support during the author's trips to South
America. L. A. Nogueira de Sa translated the abstract.

REFERENCES CITED

BORGMEIER, T. 1922 (1921). Zur lebensweise von Pseudacteon borgmeieri Schmitz (in
litt.) (Diptera: Phoridae). Zs. Deut. Ver. Wiss. Kunst Sao Paulo 2: 239-248.
BORGMEIER, T. 1925. Novos subsidies para o conhecimento da familiar Phoridae
(Dipt.). Arch. Mus. Nac. Rio de Janeiro 25: 85-281.

















Behavioral Ecology Symposium '97: Porter


BORGMEIER, T. 1962. Cinco esp6cies novas do genero Pseudacteon Coquillett. Arq
Mus. Nac. 52: 27-30.
BORGMEIER, T. 1963. Revision of the North American phorid flies. Part I. The Phori-
nae, Aenigmatiinae, and Metopininae, except Megaselia (Diptera: Phoridae).
Stud. Entomol. 6: 1-256.
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Florida Entomologist 81(3) September, 1998


THE MANIPULATION OF ARTHROPOD REPRODUCTION BY
WOLBACHIA ENDOSYMBIONTS

DENISE L. JOHANOWICZ AND MARJORIE A. HOY
Department of Entomology and Nematology, University of Florida
Gainesville, FL 32611-0620

ABSTRACT

Wolbachia are intracellular bacteria that manipulate the reproduction of their ar-
thropod hosts. The nature of the manipulation varies with Wolbachia strain, arthro-
pod taxa, and arthropod genetic system. Nonreciprocal and reciprocal reproductive
incompatibilities, sex ratio biases, and induction of thelytoky are some of the results
of Wolbachia symbiosis. The Wolbachia present in the predatory mite Metaseiulus oc-
cidentalis are genetically similar to those found in insects, and are correlated with
nonreciprocal incompatibility in crosses between infected males and uninfected fe-
males. The incompatibility phenotype includes reduced numbers of eggs, shriveled
eggs, and a male-biased sex ratio of the few resulting progeny, which may be related
to the parahaploid genetic system of this phytoseiid mite.

Key Words: symbiont, incompatibility, sex ratio, Phytoseiidae

RESUME

Wolbachia son bacteria intracelulares que manipulan la reproducci6n de sus hos-
pederos artr6podos. La forma de esta manipulaci6n varia con la sepa de Wolbachia, el
tax6n del artr6podo, y el sistema genetico del artr6podo. Incompatibilidades reproduc-
tivas reciprocas y no-reciprocas, variaciones del coeficiente sexual, e inducci6n de te-
litoquia son algunos de los resultados de la simbiosis con Wolbachia. La sepa de
Wolbachia que se encuentra en el acaro depredador Metaseiulus occidentalis es gene-
ticamente similar a la que se encuentra en insects, y esta correlacionada con incom-
patibilidad no-reciproca en cruzas entire machos infectados y hembras no infectadas.
El fenotipo de incompatibilidad incluye la producci6n de un numero reducido de hue-
vos, huevos arrugados, y un coeficiente sexual de la poca progenie que result incli-
nado hacia el macho, el cual puede estar relacionado al sistema genetico para-
haploide de este acaro fitoseido.




HISTORICAL OVERVIEW

Wolbachia are intracellular, transovarially-transmitted, rickettsial-like endosym-
bionts in the alpha-subdivision of the proteobacteria (purple bacteria). Wolbachia bac-
teria were first described from the gonadal tissues of the mosquito Culex pipiens L. in
1924 by Hertig and Wolbach. Unusual reproductive incompatibilities were described
later in Culex pipiens mosquitoes by Ghelelovitch (1952) and Laven (1951). One type
of these incompatibilities was nonreciprocal, meaning that crosses of males from pop-
ulation A with females of population B resulted in normal hybrid progeny, but crosses
of males from population B with females from population A (the reciprocal cross) re-
sulted in few viable hybrid progeny. Because the nuclear genetic makeup of the two
hybrid crosses is essentially the same and the main difference is which mother's cy-
toplasm is interacting with the nuclear genes, the incompatibilities have a cytoplas-

















Behavioral Ecology Symposium '97: Johanowicz and Hoy 311

mic inheritance pattern, also called "cytoplasmic incompatibility" (Laven 1959). In
the 1970s Yen & Barr (1971) first correlated these nonreciprocal, cytoplasmic incom-
patibilities with the presence of Wolbachia endosymbionts. They found that when
Wolbachia-infected males were treated with tetracycline (which is toxic to rickettsia-
like microorganisms), they could reproduce successfully with uninfected females.
Because Wolbachia's morphological characters are of limited value and Wolbachia
are difficult to culture outside the host (Weiss & Moulder 1984, O'Neill et al. 1992),
their presence in other arthropods was merely speculative. However, in 1992, Wolba-
chia-specific polymerase chain reaction (PCR) primers were developed (O'Neill et al.
1992). These primers, designed to be specific to Wolbachia, are also general enough to
amplify Wolbachia 16S ribosomal DNA from various insects. Reproductive anomalies
associated with the presence of an unknown rickettsia could now be correlated with
the presence of Wolbachia. For example, Wolbachia infection was confirmed in some
California populations of Drosophila simulans Sturtevant (O'Neill et al. 1992). This
symbiont was previously suspected as the causative agent of nonreciprocal reproduc-
tive incompatibilities between geographical populations ofD. simulans (Hoffmann et
al. 1986).


WOLBACHIA BIOLOGY

Wolbachia are transmitted through the egg cytoplasm, and therefore solely by fe-
males, except for one reported case of male transmission in laboratory populations of
D. simulans (Hoffmann & Turelli 1988). Wolbachia are sensitive to high temperatures
(Stevens 1989, Stouthamer et al. 1990, Girin & Bouletreau 1995, Louis et al. 1993),
and the antibiotics rifampin and tetracycline (Stouthamer et al. 1990). The only suc-
cess to date in culturing them outside the host has been in anAedes albopictus (Skuse)
cell line (O'Neill et al. 1995).
Because Wolbachia cannot be studied with traditional microbiological techniques
(Weiss & Moulder 1984), techniques such as the polymerase chain reaction (PCR) and
DNA sequencing have provided major breakthroughs in the study of these endosym-
bionts (O'Neill et al. 1992, Breeuwer et al. 1992, Rousset et al. 1992b, Stouthamer et
al. 1993). The PCR allows the amplification of a specific region of Wolbachia DNA
more than a million-fold. The presence or absence of the symbiont then can be deter-
mined by visual detection of the expected size fragment of DNA in an ethidium bro-
mide-stained agarose gel under UV light. This amplification also yields ample DNA
for sequencing and further description and characterization. DNA sequence analyses
indicate a lack of concordance between the phylogenies of the symbiont and of the
hosts, suggesting that this symbiont might sometimes be transmitted horizontally
from species to species (Rousset et al. 1992b, O'Neill et al. 1992). Recent studies with
the PCR determined that 16% of all insect species examined are infected with Wolba-
chia (Werren et al. 1995), and include representatives from a wide variety of orders
and families (Giordano et al. 1997). For an extensive review of the current knowledge
about Wolbachia, see Werren (1997).

WOLBACHIA'S EFFECTS

The effects of Wolbachia can be influenced by several factors. The strain of Wolba-
chia is important; some strains have been demonstrated to cause no reproductive al-
terations (Giordano et al. 1995). The phenotype of Wolbachia-mediated reproductive
alterations also depends on the taxonomic status of the affected arthropod (Insecta,
Arachnida, Isopoda) (see Werren 1997), as well as the genetic system of the arthropod.

















Florida Entomologist 81(3) September, 1998


It is important to consider arthropod genetic systems in order to better appreciate the
diversity of Wolbachia's effects on reproduction.
Diplo-diploid arthropods produce both sexes from fertilized eggs, each sex carrying
both the maternal and paternal sets of chromosomes throughout their lives. In haplo-
diploid arthropods, female progeny arise from fertilized eggs and are diploid, but the
male progeny arise from unfertilized eggs and are haploid, carrying only the maternal
set of chromosomes. Thelytoky is a genetic system in which virgin females produce
diploid daughters parthenogenetically, rarely producing males. In a parahaploid ge-
netic system, both sexes initially arise from fertilized diploidd) eggs, with both sets of
chromosomes. However, one chromosome set is subsequently lost in males, and the
adult male is haploid, producing sperm by a mitotic process.
When males of infected diplo-diploids mate with females lacking Wolbachia, the pa-
ternal chromosome set becomes abnormal in the fertilized egg (Kose & Karr 1995,
O'Neill & Karr 1990), resulting in the death of both male and female progeny (Hoff-
mann et al. 1986, Hsiao & Hsiao 1985). The reciprocal cross is normal. Although the
molecular mechanism of this incompatibility is not yet fully understood, it is speculated
that Wolbachia somehow "imprints" or "modifies" the paternal set of chromosomes dur-
ing spermatogenesis (Werren 1997), even though the bacteria themselves are not
present in the mature male gametes. If Wolbachia is present in the egg cytoplasm, it
can "rescue" the paternal chromosomes so that they remain normal and produce the
normal diploid sons and daughters. If no Wolbachia is present, there is no "rescue" and
those paternal chromosome set becomes abnormal, leading to embryonic death.
This same mechanism may occur in haplo-diploid insects, but with different con-
sequences. When infected haploid males mate with uninfected diploid females, the
male haploidd) progeny remain normal, but the normally diploid female embryos be-
come haploid due to abnormalities in the paternal set of chromosomes (Ryan & Saul
1968, Reed & Werren 1995). The resulting phenotype of Wolbachia-mediated incom-
patibilities in haplo-diploid species is a strongly male-biased sex ratio because of the
loss of female progeny. The haploid female embryos may die, as in some strains of the
mite Tetranychus urticae Koch (Chelicerata: Arachnida) (Vala & Breeuwer 1996), or
the haploid female embryos can become males thereby increasing the total number of
expected males, as in the wasp Nasonia vitripennis Walker (Mandibulata: Insecta)
(Breeuwer & Werren 1990, Ryan & Saul 1968).
Wolbachia can also cause bidirectional incompatibility in diplo-diploid species
(O'Neill & Karr 1990) and haplo-diploid species (Perrot-Minot et al. 1996). In this sit-
uation, two populations apparently host two different Wolbachia strains. The result is
reciprocal incompatibility, where both interpopulation crosses are incompatible.
Wolbachia induces thelytoky in some hymenopteran species, such as Tri-
chogramma (Stouthamer et al. 1990) andAphytis (Zchori-Fein et al. 1995). Wolbachia
allows these females to produce diploid daughters parthenogenetically by causing ga-
mete or chromosomal duplication early in the first mitotic division (Stouthamer & Ka-
zmer 1994).
Wolbachia causes a typical diplo-diploid incompatibility phenotype in some iso-
pods (Rousset et al. 1992a), as well as an unusual phenotype in the speciesArmadil-
lium vulgare Latr. In this species, Wolbachia suppresses the androgenic gland in
genetically male individuals, causing these male isopods to become functional females
(Rigaud et al. 1991). It is likely that, with the diversity of Wolbachia's effects on the
arthropod taxa and genetic systems described to date, there may be more Wolbachia-
mediated reproductive anomalies remaining to be described.
Because uninfected females are reproductively incompatible with infected males,
and infected females can reproduce successfully with infected and uninfected males,
infected females tend to have a reproductive advantage in polymorphic populations

















Behavioral Ecology Symposium '97: Johanowicz and Hoy 313

(Caspari & Watson 1959, Turelli & Hoffmann 1991). The D. simulans Wolbachia in-
fection has spread within and among California populations (Turelli & Hoffmann
1991, Turelli et al. 1992) since it was first documented in 1986 (Hoffmann et al. 1986).
However, the ability of Wolbachia to spread through a population is modulated by var-
ious factors, including the stability of the infection as a function of maternal trans-
mission frequency, fitness costs associated with infection, and the strength of
incompatibility (Hoffmann et al. 1990, Turelli et al. 1992, Clancy & Hoffmann 1997).
The potential for Wolbachia-infected individuals to sweep through a population
may be a useful phenomenon in the control of arthropod-borne pathogens. Efforts are
under way to genetically engineer insects to be refractory to disease agents like those
causing malaria or Chagas' disease (Beard et al. 1993). A mechanism is needed to en-
able these transformed arthropods to replace the wild-type insects already present in
the field population. The ability of Wolbachia infection to spread through a popula-
tion, as documented in D. simulans, could be harnessed as a mechanism to help drive
a genetically altered trait through a population if the trait hitchhikess" with the Wol-
bachia-infected cytoplasm (Caspari & Watson 1959, Beard et al. 1993). However, a
fuller understanding of Wolbachia biology will be necessary before it can be used suc-
cessfully as a drive mechanism (Werren 1997).
Wolbachia symbiosis may have other important effects. Wolbachia-mediated re-
productive isolation may be one mechanism that could allow sympatric speciation to
occur (Laven 1959, Werren 1997, Giordano et al. 1997). Wolbachia alters sex ratios
and progeny survival and, as a consequence, may affect laboratory experiments and
insect management in field programs. Wolbachia infection may have implications for
mass rearing projects, especially if the bacteria have an influence on the quality of the
natural enemies (Steiner 1993) or affect the rate of population increase of the individ-
uals being reared.

WOLBACHIA IN THE PREDATORY MITE METASEIULUS OCCIDENTALIS: A CASE STUDY

The predatory mite Metaseiulus (= Typhlodromus or Galendromus) occidentalis
(Nesbitt) is an important natural enemy of Tetranychus species, including Tetrany-
chus urticae Koch. This predatory mite is used as a biological control agent in various
crops in the western United States (Hoyt 1969, Flaherty & Huffaker 1970, Hoyt &
Caltagirone 1971, Hoy 1985). Biological characteristics that affect these predators'
rate of population increase are of particular importance (Sabelis 1985), including the
presence of nonreciprocal reproductive incompatibilities between different strains or
populations (Hoy 1985). Such nonreciprocal reproductive incompatibilities have been
reported in M. occidentalis, and are associated with shriveled eggs, low numbers of
eggs, low survival of immature stages, and reduced fecundity in surviving F, individ-
uals (Croft 1970, Hoy & Knop 1981, Hoy & Standow 1982, Hoy & Cave 1988). Studies
on the mode of inheritance of pesticide resistance have been affected by nonreciprocal
cross incompatibilities (Hoy & Knop 1981, Hoy & Standow 1982). Nonreciprocal in-
compatibilities have interfered with hybridization studies between different phy-
toseiid mite populations (one method of determining species designations), including
studies with M. occidentalis (Croft 1970), Typhlodromus annectens DeLeon (Mc-
Murtry & Badii 1989), and Amblyseius addoensis van der Merwe and Ryke (Mc-
Murtry 1980).
The cause of the nonreciprocal reproductive incompatibilities was unknown in
these phytoseiids. An intracellular rickettsia-like microorganism was found by Hess
& Hoy (1982) in M. occidentalis eggs and ovaries through light and electron micros-
copy. This observation, along with the nonreciprocal nature of the incompatibilities,
led Hoy & Cave (1988) to speculate that a cytoplasmic factor may be responsible for

















Florida Entomologist 81(3) September, 1998


the observed reproductive aberrations seen in M. occidentalis, perhaps due to the
presence of Wolbachia.
By using Wolbachia specific PCR primers which amplify the 16S ribosomal RNA
and ftsZ genes, we determined that Wolbachia was present in both the predatory mite
and its prey, Tetranychus urticae (Johanowicz & Hoy 1996). Unexpectedly, the Wolba-
chia DNA sequences from the two mite species were nearly identical to each other and
to those from insects, including the type species Wolbachia pipientis from the mos-
quito Culex pipiens. Whether the Wolbachia from the mites are truly this similar to
each other and to the symbionts from insects remains to be answered, because these
genes are too conserved to resolve this question.
In order to study the biological effects of Wolbachia infection, it is crucial to obtain
a population without the symbionts with which infected individuals can be crossed or
compared. Rearing these mites at high temperatures (33 C) eliminated Wolbachia in
the treated mites, as indicated by a PCR assay for infection status, and allowed cross-
ing studies to be conducted. Interestingly, the incompatibility phenotype in M. occi-
dentalis was a unique combination of reduced progeny production (as in diplo-
diploids) and a skewed sex ratio (as in haplo-diploids) of the few resulting progeny,
when infected males were crossed with cured females (Johanowicz & Hoy 1998). This
phenotype may be due to the parahaploid genetic system (Hoy 1979) of this mite. Nel-
son-Rees et al. (1980) demonstrated cytologically that both male and female M. occi-
dentalis are diploid at the beginning of embryonic development, but at the onset of the
reductional division 24-48 hours after egg deposition, one of the sets (most likely the
paternal set) becomes heterochromatinized and excluded from the nucleus, resulting
in haploid males.

CONCLUSION

Wolbachia manipulate arthropod reproduction by causing nonreciprocal incom-
patibility, bidirectional incompatibility, skewed sex ratios, and thelytoky, depending
on the Wolbachia strain, arthropod taxa, and genetic system. For example, Wolbachia
is associated with both reduced egg production and a male-biased sex ratio of the few
remaining progeny in M. occidentalis, a predatory mite with a parahaploid genetic
system.
Interesting questions remain to be answered about Wolbachia symbiosis in M. oc-
cidentalis and in other arthropods. The exact mechanism of the reproductive manip-
ulations remains unknown. A more detailed phylogenetic analysis of the Wolbachia in
its various hosts using less conserved genes should provide a better estimate of the
evolutionary relationships between the symbionts. Further study of Wolbachia infec-
tion dynamics may determine it's potential use as a drive mechanism. Other conse-
quences of Wolbachia infection remain to be described. For example, Hsiao (1996)
indicated that Wolbachia infection may be responsible for protecting the Western bio-
type of the alfalfa weevil from a parasitoid. Because of the complex interactions be-
tween this microorganisms and its arthropod hosts, a multidisciplinary approach will
be helpful in answering many of these remaining questions.

ACKNOWLEDGMENTS

Thanks to J. Sivinski and T. Walker for including this paper in the Behavioral Ecol-
ogy Symposium, to J. Sivinski and J. Nation for helpful comments on this manuscript,
and to L. Keal and A. Jeyaprakosla for technical assistance during this project. This
work was supported with funds from the Davies, Fischer, and Eckes Endowment in
Biological Control. This is University of Florida journal publication R-06194.

















Behavioral Ecology Symposium '97: Johanowicz and Hoy 315

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Florida Entomologist 81(3) September, 1998


EFFECTS OF SUGAR/FLOUR SPHERES COATED WITH PAINT
AND INSECTICIDE ON ALIGHTING FEMALE CERATITIS
CAPITATA (DIPTERA: TEPHRITIDAE) FLIES

XING PING HU', JIAN JUN DUAN2 AND RONALD J. PROKOPY1
1Department of Entomology, University of Massachusetts, Amherst, MA 01003

2Kauai Agricultural Research Center, Department of Entomology
University of Hawaii, Kapaa, HI 96746

ABSTRACT
We studied the behavior and fate of mature, wild-origin Ceratitis capitata (Wiede-
mann) females allowed to feed on 7-cm-diam spheres comprised of a mixture of sugar,
flour and glycerin and coated with yellow latex paint containing either no insecticide,
dimethoate (1.5% a.i.) or imidacloprid (1.5% a.i.). Females feeding on imidacloprid-
treated spheres for 20 sec exhibited very little tendency to forage within host plants
or to lay eggs either shortly after or 24 h after feeding, and suffered high mortality
within 48 h. In contrast, females feeding on dimethoate-treated spheres for 180 sec
exhibited, shortly thereafter, a tendency to forage within host plants and to lay eggs
about equal to that of females feeding on untreated spheres, although they suffered
high mortality within 24 h. In a field test, imidacloprid-treated sugar/flour spheres
provided a significant level of protection of fruit from oviposition by C. capitata during
24 h periods (equal to that provided by sticky yellow spheres), whereas dimethoate-
treated spheres did not. Further research on long-term activity of pesticide residue
and on sphere performance under natural conditions will be necessary, however, be-
fore sugar/flour spheres coated with yellow latex paint and insecticide can be recom-
mended for control of C. capitata.

Key Words: Mediterranean fruit flies, imidacloprid, dimethoate, spheres

RESUME
Estudiamos el comportamiento y el destino de moscas hembra maduras de Cera-
titis capitata (Wiedemann) de origen silvestre alas que se les permiti6 alimentarse so-
bre esferas de 7 cm de diametro compuestas de una mezcla de azucar, harina y
glicerina cubiertas con pintura de latex amarilla que contiene ya sea ningun insecti-
cida, dimetoato (1.5% i.a.) o imidacloprid (1.5% i.a.). Las moscas hembra que se ali-
mentaron en esferas con imidacloprid por 20 segundos exhibieron una muy baja
tendencia a alimentarse en plants hospederas o a poner huevecillos poco despues de
alimentarse o 24 horas despues de alimentarse y sufrieron una tasa de mortandad
alta dentro de un period de 48 horas. En cambio, las hembras que se alimentaron en
esferas con dimetoato por 180 segundos exhibieron poco despues niveles de tendencia
a alimentarse en plants hospederas y a poner huevos aproximadamente igual a los
demostrados por las hembras que se alimentaron en esferas no tratadas con insecti-
cidas, aunque sufrieron una tasa de mortandad alta dentro de un period de 25 horas.
En un experiment de campo, esferas de azucar y harina tratadas con imidacloprid
proporcionaron un nivel significativo de protecci6n a la fruta en contra de oviposici6n
por C. capitata durante periods de 24 horas (igual al que proporcionaron las esferas
amarillas pegajosas), mientras que las esferas tratadas con dimetoato no lo lograron.
Es necesario hacer investigaci6n adicional sobre la actividad a largo plazo de residues
de pesticides y sobre el funcionamiento de las esferas bajo condiciones naturales antes
de que puedan ser recomendadas las esferas amarillas de azucar y harina cubiertas
con pintura de latex e insecticide para el control de C. capitata.

















Hu et al.: Medfly Behavior


The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is an important pest
of fruits and vegetables on several continents. A variety of traps has been developed
for capturing C. capitata females and males (Heath et al. 1995), including sticky-
coated fruit-mimicking sphere traps (Nakagawa et al. 1978; Cytrynowicz et al. 1982;
Katsoyannos 1987; Katsoyannos & Hendrichs 1995). Yellow spheres have proven to be
the most attractive colored spheres for C. capitata females, especially when 7 cm diam
in size (Katsoyannos 1987).
Another tephritid, the apple maggot fly, Rhagoletis pomonella (Walsh), has been
successfully controlled in commercial apple orchards using 8-cm-diam sticky-coated
red wooden spheres hung (when unbaited) on every tree in an orchard or (when
baited) on perimeter apple trees so as to surround an orchard (Prokopy & Mason
1996). Because considerable labor and expense are associated with cleaning such
spheres every other week to maintain fly-capturing effectiveness (Duan & Prokopy
1995b), an alternative to sticky as the fly killing agent has been sought in the form of
a mixture of pesticide, fly feeding stimulant and residue extending agent that could
be applied to the sphere surface and kill alighting flies through ingestion of pesticide
(Duan & Prokopy 1995b). A far less amount of pesticide is required to achieve mortal-
ity via ingestion than through tarsal contact alone (Duan & Prokopy 1995a). One
shortcoming of this approach, however, has been rapid disappearance of fly feeding
stimulant (sugar) during rainfall (Duan & Prokopy 1995a). To address this shortcom-
ing, a new type of sphere has been created to replace wood as the sphere body (Hu et
al. 1998). It consists of sugar entrapped in a mixture of gelatinized flour and glycerin.
These ingredients are formed into a sphere, which is then dried and coated with a
mixture of latex paint and insecticide. A sphere of this sort maintains a continuous
supply of fly feeding stimulant on the sphere surface, even under rainfall, with latex
paint acting as a residue extending agent for the insecticide (Hu et al. 1998). To date,
two insecticides have shown more promise than any others tested when combined
with latex paint applied to sugar/flour spheres: dimethoate (Duan & Prokopy 1995a)
and imidacloprid (Hu & Prokopy 1998).
Here, we evaluated the potential of insecticide-treated yellow-colored sugar/flour
spheres for use in controlling C. capitata females by comparing the effectiveness of
dimethoate and imidacloprid. First, we asked which of these two insecticides ulti-
mately yielded the greatest reduction in oviposition and the greatest mortality of
alighting females. Next, we asked which of these two insecticides most strongly re-
duced intra-plant foraging and ovipositional activities of females between the time of
alighting on spheres and the occurrence of mortality. Finally, we asked which of these
two insecticides on spheres offered the greatest degree of protection of fruit against C.
capitata oviposition.


MATERIALS AND METHODS

C. capitata used in all greenhouse trials originated as larvae from infested fruit
collected in Hilo, Hawaii. Upon eclosion, both sexes were maintained together in 30 x
30 x 30 cm cages supplied with enzymatic yeast hydrolysate, sucrose and water until
females were mature and tested at 14-21 days of age. Females were deprived of all
food, but not water, 18 h before initial testing.
Spheres used in all experiments were similar to those described by Hu et al.
(1998). Sucrose (60g) was dissolved in fructose syrup (55 ml), water (40 ml) and glyc-
erin (20 ml), following which pregelatinized corn flour (50g) and wheat flour (50g)
were added, mixed and heated in a microwave oven. The resulting dough was allowed
to cool before it was formed into a 7-cm-diam sphere, threaded with a wire to facilitate

















Florida Entomologist 81(3) September, 1998


hanging. It was then dried in a regular oven, after which it received a coat of gloss yel-
low latex enamel paint (Glidden, Cleveland OH) as protectant. Then spheres received
a second coating of the same paint containing either 1.5% a.i. of dimethoate (Digon
400, Wilbur-Ellis, Fresno CA), 1.5% a.i. of imidacloprid (Provado, Bayer, Kansas City,
MO) or no insecticide, which we term dimethoate-treated, imidacloprid-treated or un-
treated spheres, respectively. Due to constraints of fly availability, we began testing
one day after spheres received the second coating of paint. To elicit fly feeding re-
sponse, 20% sucrose was added to the paint applied in the second coating. Three days
are usually required for sufficient sucrose from the sphere body to penetrate paint
and stimulate fly feeding (Hu et al. unpublished). For brevity, we hereafter consider
the second coating simply as a mixture of latex paint and insecticide, not explicitly ac-
knowledging the sucrose present in the mixture at application.
Greenhouse experiments were conduced in 70 x 70 x 70 cm screen cages (open to
the front), and protected above from direct sunlight with a covering of white paper.
Each cage contained a small, non-fruiting potted coffee plant whose canopy was about
50 cm diam and had about 50 leaves. A sphere was hung near the front edge of the
canopy. During 0900-1600 h, we released females singly onto the surface of a sphere,
using a small piece of paper dipped in a 20% sucrose solution and attached to a probe
to transfer the fly from a holding cage to the sphere. In the first greenhouse experi-
ment, each female was allowed to remain on a sphere until it departed or fell due to
poisoning. Total duration of stay and total time of feeding were recorded. Each fly was
then transferred immediately to a 120 cm3 plastic cup containing sucrose, water and
an uninfested kumquat as an ovipositional site. After 48 h, the female was classified
as being alive, dead or moribund (able to move but not crawl or fly and considered
dead in data analysis) and the number of eggs laid was counted.
In the second greenhouse experiment, females were again transferred individually
onto a sphere but allowed to feed only for a prescribed maximum amount of time,
which was equivalent to the median duration of feeding in the first experiment: 220,
180 and 20 sec, respectively, for untreated, dimethoate-treated, and imidacloprid-
treated spheres. Following feeding for this length of time or following departure or
falling from a sphere (if a female left before reaching this allowable duration of feed-
ing), we immediately transferred the female onto a leaf at the center of the plant can-
opy and removed the sphere from the cage. We recorded duration of fly stay on the
plant (up to 15 min) and counted all leaves visited by flight or crawling within this pe-
riod as a measure of foraging propensity. Thereafter, the female was transferred to a
kumquat fruit hung from the plant. We counted all ovipositional bouts of the female
during the next 5 min as a measure of propensity to oviposit. After this the female was
transferred to a plastic cup with sucrose and water for 24 h, at which time females
still alive were again assessed by repeating the above protocol.
In a field experiment, we compared the number of eggs laid by wild-population C.
capitata females in kumquats protected by pesticide-treated or sticky-coated sugar/
flour spheres or in unprotected kumquats. The experiment was conducted in a coffee
plantation (on Kauai) harboring a moderate population of females that had virtually
no access to natural oviposition sites because nearly all coffee berries had been picked
or fallen. About 3 m from the end of each of 20 rows of coffee plants and about 10 m
from the nearest neighboring test sites, we hung two uninfested kumquats about 6 cm
apart, attached to branchlets by twist ties. We also hung two same-type spheres, each
about 12 cm from the nearest kumquat. We cleared the area nearby of leaves to permit
visibility of fruits and spheres. Each site was baited with an aqueous extract of ripe
coffee fruit as an ovipositional attractant (Prokopy et al. 1997) and an aqueous solu-
tion of Nulure as a feeding attractant (Steiner 1952; Wakabayashi and Cunningham
1991). Solutions were applied to cotton dental wicks in separate glass vials. There

















Hu et al.: Medfly Behavior


TABLE 1. BEHAVIOR, OVIPOSITIONAL PROPENSITY AND FATE OF CERATITIS CAPITATA FE-
MALES DURING OR AFTER EXPOSURE ON YELLOW PAINT/SUGAR-COATED SUGAR/
FLOUR SPHERES IN GREENHOUSE ASSAYS.

Type of Sphere
No.
Females Treated with Treated with
Parameter Measured Tested Untreated Dimethoate Imidacloprid

Mean Duration of Stay (sec)' 20 564a 344b 238b

Mean Duration of Feeding (sec)' 20 333 a 231a 42b
Mean No. Eggs Laid when 9.9 a 1.0b
Confined with Kumquats during
Next 48 h' 20 1.0b
% Mortality after 48 h2 20 90 85

Values within the same row followed by the same letter are not significantly different according to one-way
ANOVA (following square root transformation) and the least significant difference test criterion at the 0.05 level.
For mean duration of stay, F = 7.67, df = 59, P < 0.001. For mean duration of feeding, F = 10.61, df = 59, P <
0.0001. For mean number of eggs laid, F = 23.99, df = 59, P < 0.000.
There is a significant difference among values in this row according to a Chi-square test for heterogeneity (P
< 0.0001).


were five replicates of each of four treatments: no spheres, or sugar/flour spheres
coated either with sticky, with paint containing 1.5% a.i. dimethoate, or with paint
containing 1.5% a.i. imidacloprid. Initially, we included pesticide-free sugar/flour
spheres as a fifth treatment. Unfortunately, on the first day, curious bypassers dam-
aged some of these spheres. Because we had no replacements, we were obliged to be-
gin the experiment anew without this treatment. Treatments within a replicate were
rotated daily for 4 days i.e. until each treatment was at each site once. Kumquats were
removed daily for counting eggs and replaced with fresh kumquats. Odor attractants
were renewed daily.
All data obtained, except those analyzed as proportions, were subjected to square
root transformation to stabilize variance. For data in Table 1, differences in percent
mortality among treatments were compared using a X2 test for heterogeneity. All other
data in Table 1 were subjected to one-way ANOVA. In Table 2, duration of fly resi-
dence on plants was divided into 3 groups (1-120 sec, 121-300 sec and 301-900 sec).
Data were analyzed using X2tests for heterogeneity. Other data in Table 2 were sub-
jected to one-way ANOVA (for data 0 h after exposure) or Kruskal-Wallis nonparamet-
ric one-way ANOVA (for data 24 h after exposure). Field test data in Table 3 were
subjected to one-way ANOVA.


RESULTS

In the first greenhouse experiment (Table 1), females stayed significantly longer
on untreated than on dimethoate- or imidacloprid-treated spheres and fed signifi-
cantly longer on untreated and dimethoate-treated spheres than on imidacloprid-
treated spheres. During the next 48 h, under confinement with food and fruit, females
that had been on untreated spheres laid about 10 times more eggs than females that
had been on dimethoate- or imidacloprid-treated spheres. At 48 h, few females that
had been on untreated spheres were classified as dead compared with females on in-
secticide/sugar treated spheres (Table 1).























TABLE 2. FORAGING BEHAVIOR OF C. CAPITATA FEMALES ON HOST PLANTS AND SUBSEQUENT OVIPOSITIONAL PROPENSITY AND FATE FOLLOWING
FEEDING FOR 220, 180 OR 20 SEC, RESPECTIVELY, ON UNTREATED, DIMETHOATE-TREATED OR IMIDACLOPRID-TREATED YELLOW PAINT-
COATED SUGAR/FLOUR SPHERES IN GREENHOUSE ASSAYS.

Type of Sphere to Which Female Was Exposed before Transferred to Plant at


0 h after Exposure


24 h after Exposure


Parameter Measured


No. Treated
Females with
Tested Untreated Dimethoate


% of Females Staying on 120 sec' 15
Plant for
300 sec' 15
900 sec' 15


Mean No. Leaves Visited2
Mean No. Flights to
Leaves2
Mean No. Ovipositional
Bouts2
% Mortality after 24 h'


No. Treated
Treated with Females with
Imidacloprid Tested3 Untreated Dimethoate


100 100 53 14,3,8 93 67


73 93 40 14,3,8 79
40 80 20 14,3,8 71


15 7.0a
15 6.1a

15 0.9a

15 7


0.6b 14, 3, 8 2.6 0.0
0.6b 14, 3, 8 2.8 0.0

0.lb 14,3,8 1.0 1.0


Treated with 1
Imidacloprid

100

100
100
0.3
0.0

1.0 "
CO


80 47


'For each row at 0 h, according to Chi-square tests for homogeneity, probability of a significant difference among values was p < 0.0003, 0.006, 0.004, and 0.0003, respectively, for 120
sec, 300 sec, 900 sec and % mortality; for each row at 24 h, p < 0.189, 0.002, and 0.005, respectively, for 120 sec, 300 sec, and 900 sec.
'At 0 h after exposure, values within the same row not followed by the same letter are significantly different according to one-way ANOVA (following square root transformation) and
the least significant difference test criterion at the 0.05 level. For number of leaves visited, F = 10.27, df= 44, P < 0.000. For mean number of flights to leaves, F = 2.15, df= 44, P < 0.002.
Foe mean number of ovipositional bouts, F = 5.73, df= 44, P < 0.006. At 24 h after exposure, probability of a significant difference (based on Kruskal-Walhs nonparametric one-way ANOVA)
among values within a row was p < 0.007, 0.0001 and 0.126, respectively, for number leaves visited, number flights and number ovipositional bouts.
'Number females tested for untreated, dimethoate and imidacloprid spheres, respectively.

















Hu et al.: Medfly Behavior


TABLE 3. PROTECTION OF KUMQUAT FRUIT BY PAINT/SUGAR-COATED SUGAR/FLOUR
SPHERES AGAINST OVIPOSITION BY C. CAPITATA FEMALES IN THE FIELD.

Mean No. Eggs Laid in Kumquats Protected by'

No. Replicates Dimethoate Imidacloprid
Per Treatment No Spheres Spheres Spheres Sticky Spheres

20 18.3a 14.5ab 7.4b 8.3b

Values followed by the same letter are not significantly different according to the least significant difference
test criterion at the 0.05 level. F = 3.50, df = 19, P < 0.033.


In the second greenhouse experiment (Table 2), when assessed for propensity to
forage on fruitless coffee plants immediately after feeding on a sphere for an amount
of time equivalent to the median value observed in the first greenhouse experiment,
females from imidacloprid-treated spheres behaved significantly different from fe-
males on untreated or dimethoate-treated spheres. The former visited only 11% as
many leaves and made only 14% as many flights as females from dimethoate-treated
spheres, which were not significantly different in these characteristics from females
from untreated. Moreover, when exposed to kumquat fruit for 10 minutes upon depar-
ture or removal from a plant, females from imidacloprid-treated spheres engaged in
only about 10% as many ovipositional bouts as females from dimethoate-treated or
untreated spheres. At 24 h, only 7% of females from untreated spheres were dead
compared with 80 and 47%, respectively, of females from dimethoate- and imidaclo-
prid-treated spheres. When, in the second greenhouse experiment, females alive at 24
h post-exposure to spheres were re-evaluated for foraging propensity, essentially none
of those from dimethoate- or imidacloprid-treated spheres visited any leaves by either
flying or crawling (Table 2). Those from imidacloprid-treated spheres remained
largely motionless. Numbers of ovipositional bouts per female were initially about the
same as those found at 0 h after exposure to spheres for each treatment.
In the field experiment, imidacloprid-treated spheres protected kumquats over 24
h periods against oviposition by wild C. capitata females to a degree equal to that af-
forded by sticky spheres and numerically (although not significantly) better than that
provided by dimethoate-treated spheres (Table 3). Among all tephritid females cap-
tured on the sticky spheres, 94% were C. capitata, suggesting a very high probability
that the tephritid eggs in the kumquats were deposited by C. capitata, not by other te-
phritid flies.

DISCUSSION
Our findings indicate that sugar/flour spheres containing the insecticide imidaclo-
prid at 1.5% active ingredient in the surface coating of yellow latex paint are highly
effective in immediately immobilizing C. capitata females that alight and feed upon
them for at least 20 sec. Such females were essentially unable to forage within host
plants and had a low propensity to lay eggs either minutes after or a day after expo-
sure to spheres. Nearly 50% died within 24 h and 85% died within 48 h of feeding. In
contrast, females alighting and feeding for at least 180 sec upon sugar/flour spheres
containing the insecticide dimethoate at 1.5% active ingredient in the surface coating
of yellow latex paint were not immobilized immediately after feeding and in fact were
able to forage within host plants and lay eggs equally as well as females that fed on
sugar/flour spheres lacking insecticide. It was only after some undetermined amount

















Florida Entomologist 81(3) September, 1998


of time (but less than 24 h) following feeding on sugar/flour spheres containing
dimethoate that females from such spheres suffered ill effects and a high probability
of death.
Even though in the field experiment, imidacloprid-treated spheres offered a signif-
icant degree of protection of kumquats against egglaying by C. capitata over 24 h pe-
riods, whereas dimethoate-treated spheres did not, research needs to be carried out to
determine if imidacloprid-treaded spheres have as much residual activity as
dimethoate-treated spheres following the weathering action of rainfall and sunlight.
In this vein, we did in fact exposed imidacloprid-treated, dimethoate-treated and un-
treated spheres to outdoor weather for 3 weeks following the experiments reported
here but found that C. capitata females were very reluctant to feed on any of the
spheres, even though to human taste, there was ample sugar on the sphere surface.
A high proportion of the surface of each exposed sphere was covered with growth of
microorganisms, which seemingly acted to deter fly feeding. These factors, along with
identification of powerful odors to attract mature C. capitata females to yellow
spheres (Katsoyannos et al. 1997; Prokopy et al. 1997), will need to be examined fur-
ther to allow development of yellow sugar/flour spheres for potential direct control of
C. capitata.

ACKNOWLEDGMENTS

We thank Baruch Shasha for making the sugar/flour spheres and Terri Moats for
assistance in examining kumquats for eggs. We are grateful to an anonymous re-
viewer for valuable comments. This work was supported by the Massachusetts Soci-
ety for Promoting Agriculture.

REFERENCES CITED

CYTRYNOWICZ, M., J. MORGANTE, AND H. M. L. DESOUZA. 1982. Visual response of
South American fruit flies, Anastrepha fraterculus, and Mediterranean fruit
flies, C. capitata, to colored rectangles and spheres. Environmental Entomol-
ogy 11: 1202-1210.
DUAN, J. J., AND R. J. PROKOPY. 1995a. Development of pesticide-treated spheres for
controlling apple maggot flies: pesticides and residue-extending agents. Jour-
nal of Economic Entomology 88: 117-126.
DUAN, J. J., AND R. J. PROKOPY. 1995b. Control of apple maggot flies with pesticide-
treated spheres. Journal of Economic Entomology 88: 700-707.
HEATH, R. R., N. D. EPSKY, A. GUZMAN, B. D. DUEBEN, A. MANUKIAN, AND W. L.
MEYER. 1995. Development of a dry plastic insect trap with food-based syn-
thetic attractant for the Mediterranean and Mexican fruit flies (Diptera: Te-
phritidae). Journal of Economic Entomology 88: 1307-1315.
Hu, X. P., B. S. SHASHA, M. R. MCGUIRE, AND R. J. PROKOPY. 1998. Controlled release
of sugar and toxicant from a novel device for controlling pest insects. Journal
of Controlled Release. 50: 257-265.
Hu, X. P., AND R. J. PROKOPY. 1998. Lethal and sublethal effects of imidacloprid on
apple maggot fly, Rhagoletis pomonella (Diptera: Tephritidae). Journal of Ap-
plied Entomology. 122: 37-42.
KATSOYANNOS, B. I. 1987. Effects of color properties of spheres on their attractiveness
for Ceratitis capitata flies in the field. Journal of Applied Entomology 104: 79-85.
KATSOYANNOS, B. I., AND J. HENDRICHS. 1995. Food bait enhancement of fruit mimics
to attract Mediterranean fruit fly females. Journal of Applied Entomology 119:
211-213.
KATSOYANNOS, B. I., N. A. KOULOUSSIS, AND N. T. PAPADOPOULOS. 1997. Response of
Ceratitis capitata to citrus chemicals under semi-natural conditions. Entomo-
logia Experimentalis et Applicata 82: 181-188.
















Hu et al.: Medfly Behavior 325

NAKAGAWA, S., R. J. PROKOPY, T. T. Y. WONG, J. S. ZEIGZER, S. MITCHELL, T. URAGO,
AND E. HARRIS. 1978. Visual orientation of Ceratitis capitata to fruit models.
Entomologia Experimentalis et Applicata 24: 193-198.
PROKOPY, R. J., AND J. MASON. 1996. Behavioral control of apple maggot flies. pp. 555-
559 in B. A. McPheron and G. J. Steck (eds.). Fruit Fly Pests: a World Assess-
ment of Their Biology and Management. St. Lucie Press, Delray Beach, FL.
PROKOPY, R. J., T. W. PHILLIPS, R. I. VARGAS, AND E. B. JANG. 1997. Defining sources
of coffee plant odor attractive to Ceratitis capitata flies. Journal of Chemical
Ecology 23: 1577-1587.
STEINER, L. F. 1952. Fruit fly control in Hawaii with poison-bait sprays containing
protein hydrolysates. Journal of Economic Entomology 45: 838-843.
WAKABAYASHI, M., AND R. T. CUNNINGHAM. 1991. Four-component synthetic food
odor bait for attracting both sexes of melon fly. Journal of Economic Entomol-
ogy 84: 1672-1676.


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Stoetzel & Miller:Aphids on Peach in the US.


APHIDS (HOMOPTERA: APHIDIDAE) COLONIZING PEACH IN
THE UNITED STATES OR WITH POTENTIAL FOR
INTRODUCTION

MANY B. STOETZEL AND GARY L. MILLER
Systematic Entomology Laboratory, Agricultural Research Service
U.S. Department of Agriculture, Beltsville, MD 20705 USA

ABSTRACT

Eleven aphid species known to colonize peaches in the United States and one spe-
cies not known from the United States are described and illustrated.Aphis spiraecola
Patch, Brachycaudus helichrysi (Kaltenbach), Brachycaudus persicae (Passerini),
Brachycaudus schwartzi (B6rner), Hyalopterus pruni (Geoffroy), Hysteroneura setar-
iae (Thomas), Macrosiphum euphorbiae (Thomas), Myzus cerasi (F.), Myzus persicae
(Sulzer), Myzus varians Davidson, Pterochloroides persicae (Cholodkovsky), and Rho-
palosiphum nymphaeae (L.) are included in the present paper. A brief summary of
taxonomic characters, usual hosts, and distribution within the United States are
given for each species. Pictorial and dichotomous keys are included to aid personnel
charged with detection, identification, and control of aphids associated with peaches
in the United States.

Key Words: taxonomic keys, identification, control, distribution, Prunus persica

RESUME

Son descritas e ilustradas las once species de afidos que se conocen y que coloni-
zan duraznos en los Estados Unidos y una especie que no se conoce en los Estados
Unidos. Se incluyen en este trabajo a las species Aphis spiraecola Patch, Brachycau-
dus helichrysi (Kaltenbach), Brachycaudus persicae (Passerini), Brachycaudus
schwartzi (B6rner), Hyalopterus pruni (Geoffroy), Hysteroneura setariae (Thomas),
Macrosiphum euphorbiae (Thomas), Myzus cerasi (Fabricius), Myzus persicae (Sul-

















Florida Entomologist 81(3) September, 1998


zer), Myzus varians Davidson, Pterochloroides persicae (Cholodkovsky), y Rhopalosi-
phum nymphaeae (L.). Se present para cada especie un resume breve de los
caracteres taxon6micos, hospederos comunes, y su distribuci6n dentro de los Estados
Unidos. Se incluyen claves pict6ricas y dic6tomas para ayudar a personal encargado
de la detecci6n, identificaci6n, y control de los afidos asociados con los duraznos en los
Estados Unidos.




Peaches (Prunus persica Siebold & Zuccarini) are widely grown for both commer-
cial markets and home use. In 1992, more than 226,000 acres were under peach cul-
tivation in the United States (Anonymous 1994). That same year, over 2.26 billion
pounds of peaches were harvested with California responsible for more than half the
total crop (Anonymous 1994). Preliminary data valued the 1995 peach crop at over
$412 million (Anonymous 1996).
Several species of aphids can become established on peaches. When the colonies of
aphids are large, they can greatly reduce plant vitality or even kill the plant through
mechanical injury. This is especially true in a nursery situation. Feeding aphids also
produce honeydew, a sticky substance that is potentially damaging. As aphids feed,
honeydew is excreted and accumulates on the leaves and developing fruits. Honeydew
can serve as a substrate for bacteria, yeast, and filamentous fungal growth which re-
duce plant vigor. Large amounts of honeydew on the developing fruit can cause split-
ting and fruit cracking (Barnett & Rice 1992) making the peaches unsuitable for the
consumer market. Additionally, some aphids can transmit plum pox virus (= sharka
disease) which affects peaches.
The aphid fauna associated with peaches in the United States includes at least 11
species that commonly colonize the trees. A brief summary of taxonomic characters,
hosts, worldwide distribution, and U.S. distribution is given for each of the 11 species:
Aphis spiraecola Patch, Brachycaudus helichrysi (Kaltenbach), Brachycaudus persi-
cae (Passerini), Brachycaudus schwartzi (Borner), Hyalopterus pruni (Geoffroy), Hys-
teroneura setariae (Thomas), Macrosiphum euphorbiae (Thomas), Myzus cerasi (F.),
Myzus persicae (Sulzer), Myzus varians Davidson, and Rhopalosiphum nymphaeae
(L.). We are also including information on Pterochloroides persicae (Cholodkovsky), a
known pest of peaches, other Prunus spp. (e.g. almond, apricot, and plum), and apples.
Although currently not recorded in the United States, P. persicae has extended its
range into Europe and northern Africa (Stoetzel 1990). Trade between these regions
and the United States increases the chance for accidental introduction. Descriptions,
figures, and keys are included as an aid for those responsible for detection, identifica-
tion, and control of aphids associated with peaches in the United States.

MATERIALS AND METHODS

In the synonymy section, one asterisk (*) represents the name used by Palmer
(1952) and two asterisks (**) represent the name appearing in Blackman & Eastop
(1984). Common names are those approved by the Entomological Society of America
(ESA) (Stoetzel 1989).
Information on distribution and hosts is taken from labels on slides in the Na-
tional Collection of Insects, Beltsville, Maryland, and from records in Palmer (1952),
Smith & Parron (1978), and Blackman & Eastop (1984).
In the illustrated keys, the species are grouped by morphological differences in an-
tennae and antennal tubercles, coloration of legs and abdomen, cornicles, shape of

















Stoetzel & Miller:Aphids on Peach in the US.


cauda and number of caudal setae, and wing coloration and venation. Characters used
in the keys are apparent with a dissecting microscope with a minimum power of at
least 16X. Relative body size of aphid species follows the division proposed by Black-
man & Eastop (1984): body length < 2.0 mm are "small," 2.0-3.0 mm are "medium," and
> 3.0 mm = "large." Body length is measured dorsally from the center of the frons to the
end of the abdomen, excluding the cauda (see generalized aphid, Fig. 1). Length of the
antennal "terminal process" is measured as the distance between the large primary
sensorium to the tip of the last antennal segment. Length of the "base" of the antenna
is measured from the basal portion of the last antennal segment to the apex of the pri-
mary sensorium. Caudal length is measured along the midline from the beginning of
the sclerotized portion to the tip (Fig. 1). Caudal width is measured between the hard
and soft portion of the cauda (Fig. 1). The keys are not intended for identification of sin-
gle, errant aphids but should be used for individuals fully colonizing peaches. Ideally
winged aphids should develop from nymphs collected from a colony on the tree.

Aphis spiraecola Patch 1914
Figs. 1, 4, 5

Synonymy:
Aphis spiraecola Patch
**Aphis citricola van der Goot 1912
ESA approved common name: spirea aphid
Other common names: green citrus aphid
Taxonomic characters: Wingless adult female.-In life, body yellowish green to
deep green, head brownish; tibiae pale to dusky with darker apical area. Small to me-
dium sized, body length 1.8-2.1 mm, rounded. Frontal tubercles not well developed.
Antennae 6 segmented, terminal process approximately 21/3-23/ times length of base
of antennal segment VI; antennal segment III-V without secondary sensoria. Corni-
cles dark, without setae, tapered apically, 4-514 times as long as wide, slightly longer
than length of cauda. Cauda dark, elongate, more than twice as long as wide with 3-
5 pairs of lateral setae and 0-1 preapical seta.
Winged adult female.-In life, body yellowish green with head and thorax brown-
ish; hind wing with 2 oblique veins. Small to medium sized, body length 1.7-2.3 mm,
rounded. Antennae 6 segmented, terminal process approximately 214-3 times length
of base of antennal segment VI; antennal segment III with 6-8 secondary sensoria, an-
tennal segment IV with 0-2 secondary sensoria; antennal segment V without second-
ary sensoria. Cornicles dark, elongate, without setae, tapered apically, 23/4-4 times as
long as wide, slightly longer than length of cauda. Cauda dark, elongate, more than
twice as long as wide with 3-7 pairs of lateral setae and 0-1 preapical seta.
Hosts: Polyphagous, over 20 families recorded as hosts, especially Asteraceae, Ca-
prifoliaceae, Rosaceae including Prunus spp., Rubiaceae, and Rutaceae.
U.S. distribution: Widespread.
World distribution: Virtually worldwide.
Comments:Aphis spiraecola transmits 17 plant viruses (Chan et al. 1991) includ-
ing plum pox virus, which affects peaches.

Brachycaudus helichrysi (Kaltenbach 1843)
Figs. 1, 6, 7

Synonymy:
*Aphis helichrysi Kaltenbach
** Brachycaudus helichrysi (Kaltenbach)

















Hu et al.: Medfly Behavior


$ I


nnneni 21 nondi cot.

),,


anitennat (ubIeres well developed


aeraestphamen -phobiae (Thomas)
W~e cerrani (Fabricius)
4l4aU peri.mnc (Sulnr)
tfjon v rian, Davnlde

dull female Hingeadadull females
hig. 2 we Fig 3


I
rauda elongatc.
morr lnkII 2X Innger than aide
_"h

ASS




4pmhin piraecola Patch
Hylaoperspr..Far (Geoffro)
Utt'm aproaur cetaroae (Ilcomae)
Rh".plouiphm nykphe, (I.inn ).....

ad",u females winged adult frcales
Fig, 4 see i, 5


anteal tubers nt ell
3nicaeet tubc-les nat well developed


I
calida stout,
]es Ihan 2X longer ihin wide








Brachyrtdro hi'lichrysi I Kaltenbach)
Brac'hyrtd- pericae ( Pa.-erini.
Bracrhya idi trh wurTj (holrnmr
PleFoc!ktreide, pfernce (thoondL kns k)

w]ng]es dull female' winged l dull fmema e
see Pig. 6 r Pig. 7


Fig. 1. Pictorial key to 12 aphid species that potentially colonize on peaches in the
United States.


i.~.,.n ll*n


clngliss
5.ee


wingless
Wee


x- I


Ed


~ini$

















Stoetzel & Miller:Aphids on Peach in the US.


ESA approved common name: none
Other common names: peach leaf curl aphid, leaf-curl plum aphid, leaf-curling
plum aphid.
Taxonomic characters: Wingless adult female.-In life, body color varying from
green to yellow to nearly white or sometimes pink; legs pale. Small to medium sized,
body length 1.7-2.1 mm, pear shaped. Antennae 6 segmented; tubercles not well de-
veloped; terminal process approximately 2-2/2 times length of base of antennal seg-
ment VI; antennal segment III-V without secondary sensoria. Cornicles pale, apically
dusky, without setae, slightly tapering to a constricted area near apical flange; ap-
proximately 11-12/3 times as long as wide, subequal or longer than length of cauda.
Cauda pale, stout, less than twice as long as wide with 2-3 pairs of lateral setae and
1 preapical seta.
Winged adult female.-In life, body shape and coloration similar to wingless adult
female but abdomen with a dark dorsal patch that is usually confined to posterior sev-
eral segments; antennal segments I-VI dusky on slide-mounted specimens; small
sized, body length 1.2-1.4 mm. Antennae 6 segmented; tubercles not developed; ter-
minal process approximately 22/3-32/ times length of base of antennal segment VI; an-
tennal segment III with 17-23 secondary sensoria; antennal segment IV with 1-7
secondary sensoria; antennal segment V without secondary sensoria. Cornicles com-
pletely dusky, without setae, slightly tapering to a constricted area near apical flange;
approximately 2-314 times as long as wide, subequal or longer than length of cauda.
Cauda pale, stout, less than twice as long as wide with 2-3 pairs lateral setae and 1
preapical seta.
Hosts: Primary hosts are Prunus spp.; secondary hosts include species of various
Asteraceae, Boraginaceae, and sometimes Salix.
U.S. distribution: Widespread.
World distribution: Virtually worldwide.
Comments: Brachycaudus helichrysi transmits nine plant viruses (Chan et al.
1991) including plum pox virus.

Brachycaudus persicae (Passerini 1860)
Figs. 1, 6, 7

Synonymy:
*Aphis persicae-niger E. F. Smith 1890a, b
** Brachycaudus persicae (Passerini 1860)
ESA approved common name: none
Other common names: black peach aphid
Taxonomic characters: Wingless adult female.-In life, body color shiny black with
anterior and lateral areas brown; legs yellow to dusky. Small to medium sized, body
length 1.7-2.1 mm, pear shaped. Antennae 6 segmented; tubercles not well developed;
terminal process approximately 4-5 times length of base of antennal segment VI; an-
tennal segment III-V without secondary sensoria. Cornicles completely dark, without
setae, slightly tapering to apical flange; approximately 31/2-41/2 times as long as wide,
much longer than length of cauda. Cauda dark, stout, less than twice as long as wide
with 2-3 pairs of lateral setae.
Winged adult female.- In life, body shape and coloration similar to wingless adult
female; antennal segments I-VI dusky to dark on slide-mounted specimens; small to
medium sized, body length 1.6-2.2 mm. Antennae 6 segmented; tubercles not devel-
oped; terminal process approximately 4'/3-5 times length of base of antennal segment
VI; antennal segment III with 36-46 secondary sensoria; antennal segment IV with
13-21 secondary sensoria; antennal segment V with 2-4 secondary sensoria. Cornicles

















Florida Entomologist 81(3) September, 1998


completely dark, without setae, slightly tapering to apical flange; approximately 414-
5/2 times as long as wide, much longer than length of cauda. Cauda dark, stout, less
than twice as long as wide with 3-4 pairs of lateral setae.
Hosts: Primary hosts include Prunus spp., especially Prunus persica (Blackman &
Eastop 1984).
U.S. distribution: Widespread.
World distribution: Virtually worldwide.
Comments: Brachycaudus persicae is not listed as transmitting any plant viruses
(Chan et al. 1991). Colonies of B. persicae occur on the roots of Prunus in late summer
and during winter, however winter eggs are also laid (Blackman & Eastop 1984). In
the spring, large colonies cluster around leaf buds and cause the death of young trees
(Smith 1890b).

Brachycaudus schwartzi (Borner 1931)
Figs. 1, 6, 7

Synonymy:
not listed
** Brachycaudus schwartzi (Borner 1931)
ESA approved common name: none
Other common names: peach aphid
Taxonomic characters: Wingless adult female.-In life, body color varying from
dark brown to yellow brown with black dorsal abdominal patches. Small to medium
sized, body length 1.7-2.2 mm, pear shaped. Antennae 6 segmented; tubercles not well
developed; terminal process approximately 3-3'/3 times length of base of antennal seg-
ment VI; antennal segment III-V without secondary sensoria. Cornicles dark, without
setae, with slight basal constriction then slightly tapering to apical flange; approxi-
mately 2-3 times as long as wide, longer than length of cauda. Cauda dark, stout, less
than twice as long as wide with 2-3 pairs of lateral setae and 1-2 preapical setae.
Winged adult female.-In life, coloration similar to wingless adult female but body
shape more elongate; antennal segments I-VI dusky on slide-mounted specimens;
small to medium sized, body length 1.7-2.1 mm. Antennae 6 segmented; tubercles not
well developed; terminal process approximately 3-33/ times length of base of antenna
segment VI; antennal segment III with 33-40 secondary sensoria; antennal segment
IV with 4-13 secondary sensoria; antennal segment V without secondary sensoria.
Cornicles dark, without setae, with slight basal constriction then slightly tapering to
apical flange; approximately 13/-23/ times as long as wide, longer than length of
cauda. Cauda dark, stout, less than twice as long as wide with 2-3 pairs of lateral se-
tae and 1-2 preapical setae.
Hosts: Primary host is Prunus persica and occasionally P. serotina (Blackman &
Eastop 1984).
U.S. distribution: California.
World distribution: Europe, Iran, India, South America, North America
Comments: Brachycaudus schwartzi is not listed as transmitting any plant vi-
ruses (Chan et al. 1991). Spring colonies can cause severe curling and disfiguration on
peach leaves (Blackman & Eastop 1984).

Hyalopterus pruni (Geoffroy 1762)
Figs. 1, 4, 5

Synonymy:
Hyalopterus arundinis (F. 1775)

















Stoetzel & Miller:Aphids on Peach in the US.


** Hyalopterus pruni (Geoffroy 1762)
ESA approved common name: none
Other common names: mealy peach aphid, mealy plum aphid
Taxonomic characters: Wingless adult female.-In life body light green with
darker green mottling, covered with waxy powder. Medium sized, body length 2.1-2.4
mm, body elongate. Antennae 6 segmented; tubercles not well developed; terminal
process approximately 3 times length of base of antennal segment VI, antennal seg-
ment III-V without secondary sensoria. Cornicles dark, without setae, without apical
flange, 214-23/4 times as long as wide, shorter than length of cauda. Cauda dark, elon-
gate, nearly twice as long as wide with 2 pairs of lateral setae and 0-1 preapical seta.
Winged adult female.-In life abdomen green with wax patches on each segment;
hind wing with 2 oblique veins; small sized, body length 1.7-1.9 mm. Antennae 6 seg-
mented; tubercles not well developed; terminal process approximately 4 times length
of base of antennal segment VI; antennal segment III with 18-27 secondary sensoria
of variable size; antennal segment IV with 0-4 secondary sensoria; antennal segment
V without secondary sensoria. Cornicles dark, without setae, 3-3/3 times as long as
wide, shorter than length of cauda. Cauda dark, elongate, nearly twice as long as wide
with 2-3 pairs of lateral setae and 0-1 preapical seta.
Hosts: Primary hosts include several species of Prunus including Prunus persica
(Blackman & Eastop 1984).
U.S. distribution: Widespread.
Distribution in the world: Virtually worldwide.
Comments: Hyalopteruspruni is very similar to Hyalopterus amygdali (Blanchard
1840) and the relationship between them remains unresolved. Basky & Szalay-
Marsz6 (1987) found no reliable morphological differences between the two species.
However, differences in host plant selection and mate choice led those authors to be-
lieve the two species were distinct. Blackman & Eastop (1994) summarized the liter-
ature pertaining to the disposition of H. amygdali and H. pruni and treated them as
separate species.
Chan et al. (1991) recorded seven plant viruses transmitted by H. pruni, including
plum pox virus. They did not list any plant viruses associated with H. amygdali.

Hysteroneura setariae (Thomas 1878)
Figs. 1, 4, 5

Synonymy:
*Aphis setariae (Thomas)
** Hysteroneura setariae (Thomas)
ESA approved common name: rusty plum aphid
Taxonomic characters: Wingless adult female.-In life body dark reddish brown,
apical area of tibiae dark, cornicles dark to almost black, cauda pale to nearly white.
Small to medium sized, 1.7-2.3 mm, body rounded. Antennae 6 segmented; tubercles
not well developed, terminal process approximately 42/-5 times length of base of an-
tennal segment VI; antennal segment III-V without secondary sensoria. Cornicles
dark to nearly black, without setae, tapered apically, approximately 23/4-42/ times as
long as wide, longer than length of cauda. Cauda pale to nearly white, elongate, more
than twice as long as wide with 2-3 (usually 2) pairs of lateral setae.
Winged adult female.-In life coloration similar to wingless adult female; hind
wing with one oblique vein; small to medium sized, body length 1.7-2.2 mm. Antennae
6 segmented; tubercles not well developed, terminal process approximately 514-7
times length of base of antennal segment VI; antennal segment III with 13-20 second-
ary sensoria of variable size; antennal segment IV with 1-5 secondary sensoria; an-

















Florida Entomologist 81(3) September, 1998


tennal segment V without secondary sensoria. Cornicles dark to nearly black, without
setae, tapered apically, approximately 33/-51/3 times as long as wide, longer than
length of cauda. Cauda pale to nearly white, elongate, more than twice as long as wide
with 2 pairs of lateral setae.
Hosts: Primary host is usually Prunus domestic (Blackman & Eastop 1984); how-
ever, it also occurs on other species of Prunus including P. persica. Secondary hosts in-
clude numerous species of Gramineae.
U.S. distribution: Widespread.
Distribution in the world: Virtually worldwide.
Comments: Hysteroneura setariae transmits six plant viruses but is not listed as
a vector of a peach virus (Chan et al. 1991).

Macrosiphum euphorbiae (Thomas 1878)
Figs. 1, 2, 3

Synonymy:
Macrosiphum solanifolii (Ashmead 1882)
** Macrosiphum euphorbiae (Thomas)
ESA approved common name: potato aphid.
Other common names: none
Taxonomic characters: Wingless adult female.-In life, body usually of varying
shades of green or pink. Medium to large sized, body length 2.2-3.8 mm, pear shaped.
Antennae 6 segmented; tubercles well developed with inner faces divergent; terminal
process approximately 414-614 times length of base of antennal segment VI; antenna
segment III with 3-5 secondary sensoria on basal half; antennal segment IV-V without
secondary sensoria; either entirely dark or only dark apically. Cornicles entirely pale
or becoming increasingly dusky towards tip, without setae, with slight apical constric-
tion and several rows of polygonal reticulations in constricted area, approximately 6-
11'3times as long as wide, longer than length of cauda. Cauda pale, elongate, more
than twice as long as wide with 8-10 lateral setae and 2-3 dorsal preapical setae.
Winged adult female.-In life, body usually of varying shades of green or pink; hind
wing with 2 oblique veins; medium to large sized, body length 2.6-3.0 mm. Antennae 6
segmented; frontal tubercles well developed with inner faces divergent; terminal process
approximately 51/3-71/3 times length of base of antennal segment VI; antennal segment III
with 14-18 secondary sensoria on basal 3/; antennal segments IV-V without secondary
sensoria; entirely dark except for segments I and II and base of III. Cornicles sometimes
pale but usually progressively darker towards tip, without setae, with slight apical con-
striction and several rows of polygonal reticulations in constricted area, approximately
623-13 times as long as wide, longer than length of cauda. Cauda pale, elongate, more
than twice as long as wide with 8-10 lateral setae and 1-2 dorsal preapical setae.
Hosts: Primary hosts are several species of Rosa. Polyphagous and very damaging
to many other host plants of economic importance.
U.S. distribution: Widespread.
World distribution: Virtually worldwide.
Comments: Macrosiphum euphorbiae transmits 67 plant viruses but is not listed
as a vector of a peach virus (Chan et al. 1991).

Myzus cerasi (F.1775)
Figs. 1, 2, 3

Synonymy:
& ** Myzus cerasi (F.)

















Stoetzel & Miller:Aphids on Peach in the US.

.inglejs aduLI females
antennal lubirtle's .ell deploped
I


aniltln l lubtreltr dnlrrgnt


iantennlI tuberrles i'oiierginl lo noerhl Iaralltl


7-Z__


a


cornicles with several rows or pnolgonal
rrtliuljtiOns apicall II. i ind-end area



V-c rmiphm euphiora.e ( bomas)
poIato aphid


dorsum no abdomLn durk,
cornicles entirclh dark





M.


.Ifptu cemri tFabritlus}
black herry aphid

I
antennae .ilb dlrk band, on apies
e.gments L11-V and bake of VI


/PL


conTOLC re ilh Ilightl Curvature.
pale banally and dartkr aplca]L3


VrI'U rariand Darld on


cornicle I illoiut several l ru l
of polr nal reticularians

Lt SSa \ -^ 3


dorsum uolhdomen noc dark.
carnmcle may hair dark apkice



/ i


I
antennae t Liutl dark hands
on antennas egmenti






cornirlcr wit slight apical *-llinfg
and light medialcontrictiuw.
tip ma. be dark apicall)


My-,j pesclake (Sutzer)
grrrll ptrtb aplid


Fig. 2. Pictorial key to wingless adult females of four aphid species that potentially
colonize on peaches in the United States and have well developed antennal tubercles.


| k




















Hu et al.: Medfly Behavior


singed adult femNlrs
aritennal itul ser let sell deto rupted
, I


anteor nl tuberr l L dL'ergent


5X,

0 .9 _


cornicle% wi[h serral ros ir polsli.nal
r rl.ulatio.i, api[all, in ill(tentcd are,.




.itrvisriphu ealphsorb- (Thiomat)
potalO aphid


aiLl nenal tllberkt clnm rgeren to neat Il parallel


Cr"


C.


corniOlss ,ithou et l tbral rous
of petymoal r'eltlattns


terminal process >5 times length of base


cornk-les willli slight euraluire


Irrminal process <5 tlmets lengh of has






cornitleS wifh sli ght apical P weltllin rr graduall tapered


I',us an'rians D-aidson


Lornic lr dark. gradually lIJaprcd


cnrnicles pale to dusk,, nith slight apical swrllinK
and slight medial consarlction


antrieaal tubercle- nearly) parallel


antenna tuber-les conrergerl







gyeare prtor (aS urr)
green path asphd


ifvzres e rC i ( ahriins}
hlaeL cherry aphid


Fig. 3. Pictorial key to winged adult females of four aphid species that potentially
colonize on peaches in the United States and have well developed antennal tubercles.


I |


I-i .


















Stoetzel & Miller:Aphids on Peach in the US.

sinlres adull frmalt
rauds ~lIngare, mnrE than 21% longer Ihan Hide

I


Ictnth I l inrnilcie horter than Lenglh ut csauda











myifiapkr prunp (CGoffro}i
megI, plum aphid


iLhiac eomplrwly dark


length of cornicles longer [ha nI Ienp h of cauda


apkal area of lihiar dark


/ ~ -;RZ-.


cornmcle tapered apically


Rkhpaltnph urm ~ m mpkhe (L,)
,atcrlll aplihd


termlnal prc ,-e< 3 imeus lclrb of bhae





canda da rk, L ih 4-5 pairs of lateral #1e


I


terminal process 4 times length oF bas


cauda pale, alth Z-3 pair or Jultral setar


*4


Aphir rpiraectla Patch
spirea aphid


Hysrer aneura eiaiae( Ilhnma
rusty plum aphid


Fig. 4. Pictorial key to wingless adult females of four aphid species that potentially
colonize on peaches in the United States with elongate cauda and antennal tubercles
not developed.


I


I


-iurniclfs 5wollest apIall


















Florida Entomologist 81(3)


winged adult females
i-uda lungu Ec. more Ihan 2\ lunghr than nide

I .


Length 4I Lnrnirle F hr, hirrr han JIe Rtlh ifrauda










Ityaipet'ruv preei (C ffrav)
mearly plum aphid


alttlnim l tnIgmenl III wllh 6-8 Secondarr ad ensora





enda with 4-7 pairs of Lateral aetaz


/





4pAi spir-ecla Patch
spirea aphid


hind win:g rith I tra nsiersTea







cornmcles tapered apicalli


Hycsrneure relariae (Thomas)
rusty plum aphid


leIngh of co rnicles Ionngr than length fl cauda


anntena Segment 11 with 12 or more Sttolda r s oejoria




conda with 2-3 pairs of lateral setae






i-.


hind wing nith 2 transverse veins







cornic les snoJln apic.aly




Rhkpalompham aymphraeae (1..
walerlily aphid


Fig. 5. Pictorial key to winged adult females of four aphid species that potentially
colonize on peaches in the United States with elongate cauda and antennal tubercles
not developed.


September, 1998


I.




















Stoetzel & Miller:Aphids on Peach in the US.


'1ingl-s adult female
Lauda stoul., Ic than 21 longer than t ide


I


uarmtnaL prucetl antell l mE ntlt t ] *holelr 0llaM hba1e




turnhiiel truncated tViP o Hlh nuim rous relac










Phrolokuro des persli-a (Chnledkuoak,)


terminal prores > 4 imes the aknglb ofbaw




caraihles > timer a long as wide


trlmintin A13 ro ij i at I ninal b I RmentI [Il i4o r Iltan taI e




coricirlo aithoul qttat




S-------- -


terminal procas < 4 times the length of baw




corniclcs < 3 tilc as long as wide



F- L-aJ


Brur hylAym ad pe-rae (Paisen.i}
black peach aphid


I
drlrrun o a bdamrn wLllhout dark pallh;
rcrn ersC palr to du ko, .aeddl pale


dr nm of abdomen with dark patch;
cornicle and cauda dark


Br aryca.aud Aeihry llKalkelbalch) Braltttdatu tEcrr:o (iiR ntl )
peach leafcurt aphid pyall aphld

Fig. 6. Pictorial key to wingless adult females of four aphid species that potentially
colonize on peaches in the United States with stout cauda and antenna tubercles not
developed.






















Florida Entomologist 81(3)


linged a ult females
eatida sunt, less [hart ( lon ier Z h Ih iid


I 1


terminal pro-e nF a nlTnnal %egmenr 1 I shorltr thali hbas





forein, nith large distinctise dark palL-hes









plmeoA'torodrts perieCfre rChuludkoslsk)


antenna l segment V with 2-4 sf ondary senuoria




t tiles

ITi ra Ielts 4 times a^ Inng ta aid.


Bralrhy'au aus pertia (Passerim]l
black prach a hid


an rnnal segmel IlI I th 33-40 secondary setae


terminal proets of ante nal a risegm t k longer han hat*





lorening alli ul Jargt dilinriltLe dark patches





---:-1


allenllal segment V wlboul secondaryv seornia


iV V VI




corilw < 4c times a loNIDg at vide


7--0


anlentlal Segment III With 17-23 secomdar setar


cauda pale


tBrftysaudsm Ofkwrtci (Brner)
peach aphid


Brahreocaud helichryrl (Ka llnhach)
peth Iacuarl aphidl


Fig. 7. Pictorial key to winged adult females of four aphid species that potentially
colonize on peaches in the United States with stout cauda and antennal tubercles not
developed.


September, 1998


I





cau dad rkl

















Stoetzel & Miller:Aphids on Peach in the US.


ESA approved common name: black cherry aphid
Other common name: cherry blackfly
Taxonomic characters: Wingless adult female.-In life body color shiny dark
brown to black with bicolored yellow and brown antennae and legs. Small to medium
sized 1.9-2.2 mm, pear shaped. Antennae 6 segmented; tubercles well developed with
inner faces nearly parallel, terminal process approximately 2-314 times length of base
of antennal segment VI, antennal segment III-V without secondary sensoria. Corni-
cles dark, without setae, gradually tapered, approximately 5-9'/2 times as long as
wide, longer than length of cauda. Cauda dark, elongate, more than twice as long as
wide with 2-3 pairs of lateral setae.
Winged adult female.-In life body color with dorsal patch on abdomen; hind wing
with 2 oblique veins; small sized, body length 1.7-1.9 mm. Antennae 6 segmented; tu-
bercles well developed with inner faces nearly parallel, terminal process approxi-
mately 3-4 times length of base of antennal segment VI, antennal segment III with
12-16 secondary sensoria of similar size and in an irregular row; antennal segment IV
with 0-3 secondary sensoria; antennal segment V without secondary sensoria. Corni-
cles dark, without setae, gradually tapered, approximately 5-6'/3 times as long as
wide, longer than length of cauda. Cauda dark, elongate, more than twice as long as
wide with 2-3 pairs of lateral setae.
Hosts: Primary hosts include Prunus cerasus, P. avium and occasionally other spe-
cies of Prunus. Secondary hosts include species of Cruciferae, Rubiaceae, and Scro-
phulariaceae.
U.S. distribution: Widespread.
Distribution in the world: Australia, Europe, India, New Zealand, North America,
Pakistan, Turkey.
Comments: Myzus cerasi transmits six plant viruses but is not listed as a vector of
a peach virus (Chan et al. 1991).


Myzus persicae (Sulzer 1776)
Figs. 1, 2, 3

Synonymy:
& ** Myzus persicae (Sulzer)
ESA approved common name: green peach aphid
Other common name: peach-potato aphid
Taxonomic characters: Wingless adult female.-In life, body varying from green to
pale yellow. Small to medium sized, 1.9-2.4 mm, pear shaped. Antennae 6 segmented;
tubercles well developed with inner faces convergent; terminal process approximately
23/-33/ times length of base of antennal segment VI; antennal segment III-V without
secondary sensoria. Cornicles pale but tip may be dark, without setae, slight apical
swelling and slight medial constriction; approximately 43/-7 times as long as wide,
longer than length of cauda. Cauda pale to dusky, elongate, more than twice as long
as wide with 3 pairs of lateral setae.
Winged adult female.-In life, body varies from green to pale yellow with a large
dark patch on dorsum of abdomen; hind wing with 2 oblique veins; small to medium
sized, body length 1.7-2.3 mm. Antennae 6 segmented; tubercles well developed with
inner faces convergent; terminal process approximately 314-4/2 times length of base of
antennal segment VI; 8-11 secondary sensoria of similar size in a straight row on an-
tennal segment III; without secondary sensoria on antennal segments IV-V. Cornicles
dusky to dark but tip sometimes darker, without setae, slight apical swelling and
slight medial constriction; approximately 33/-6 times as long as wide, longer than

















Florida Entomologist 81(3) September, 1998


length of cauda. Cauda pale to dusky, elongate, more than twice as long as wide with
3 pairs of lateral setae.
Hosts: Primary hosts are several species of Prunus. Polyphagous and very damag-
ing to many other host plants of economic importance.
U.S. distribution: Widespread.
World distribution: Virtually worldwide.
Comments: Myzus persicae transmits 182 plant viruses including plum pox virus
(Chan et al. 1991).

Myzus varians Davidson 1912
Figs. 1, 2, 3
Synonymy:
not listed
** Myzus varians Davidson
ESA approved common name: none
Other common name: none
Taxonomic characters: Wingless adult female.-In life, body varying from light to
darker green. Small sized, body length 1.6-1.9 mm, pear shaped. Antennae 6 seg-
mented with dark bands on apices antennal segments III, IV, V, and base of VI; tuber-
cles well developed with inner faces convergent; terminal process approximately 514-
5/2 times length of base of antennal segment VI; antennal segment III-V without sec-
ondary sensoria. Cornicles pale basally and dark apically, without setae, slightly ta-
pered with slight curvature; 4-51/3 times as long as wide, longer than length of cauda.
Cauda pale, elongate, more than twice as long as wide with 3-4 pairs of lateral setae.
Winged adult female.-In life, body varies from green to blue-green with a dark
patch on the dorsum of abdomen; hind wing with 2 oblique veins; small to medium
sized, body length 1.7-2.2 mm. Antennae 6 segmented, completely dark; tubercles well
developed with inner faces convergent; terminal process approximately 514-52/3 times
length of base of antennal segment VI; antennal segment III with 5-12 secondary sen-
soria of similar size in a straight row; antennal segments IV-V without secondary sen-
soria. Cornicles dark, without setae, slightly tapered with slight curvature; 4'/3-7
times as long as wide, longer than length of cauda. Cauda pale, elongate, more than
twice as long as wide with 3-5 pairs of lateral setae.
Hosts: Primary host is Prunus persica in spring and the secondary host is Clematis
spp. in the summer. However, in North America M. varians has been collected pre-
dominately on Clematis spp.
U.S. distribution: California, Florida, Maryland, North Carolina
World distribution: Europe, East Asia, North America
Comments: Although not listed in Chan et al. (1991), M. varians has been recorded
as transmitting plum pox virus (Blackman & Eastop 1984).

Pterochloroides persicae (Cholodkovsky 1899)
Figs. 1, 6, 7

Synonymy:
not listed
** Pterochloroides persicae (Cholodkovsky)
ESA approved common name: none
Other common name: clouded peach bark aphid, cloudy-winged peach aphid
Taxonomic characters: Wingless adult female.-In life body color dark brown to
black with some white patches, dorsum of abdomen with a double row of large tuber-
cles; venter white. Large sized, body length 3.5-4.7 mm, oval. Antennae 6 segmented,

















Stoetzel & Miller:Aphids on Peach in the US.


short with apical bands on antennal segments III-VI; tubercles not well developed;
terminal process shorter than length of base antennal segment VI; antennal segment
III with 0-2 secondary sensoria; 0-1 secondary sensoria on antennal segment IV; an-
tennal segment V without secondary sensoria. Cornicles dark, truncated cones with
numerous setae, nearly as long as wide, subequal to length of cauda. Cauda dark,
stout, less than 2x longer than wide with numerous setae.
Winged adult female.-In life body color similar to wingless adult female; forewing
with large distinctive dark patches; large sized, body length 2.7-3.6 mm. Antennae 6
segmented, short, terminal process less than length of base antennal segment VI; an-
tennal segment III with 8-14 secondary sensoria of similar size; antennal segment IV
with 1-5 secondary sensoria; antennal segment V without secondary sensoria. Cornicles
dark, truncated cones with numerous setae, nearly as long as wide, subequal to length
of cauda. Cauda dusky, stout, less than 2x longer than wide with numerous setae.
Hosts: Principle hosts include Prunus spp. (almond, apricot, peach), however P.
persicae has also been recorded from other plants including Citrus and Malus. Ptero-
chloroides persicae is found living on large branches and trunks of its host (Blackman
& Eastop 1994).
U.S. distribution: Not known to occur in the United States.
Distribution in the world: Recorded from India, Pakistan, the Middle East, the
Mediterranean area, Italy and Yugoslavia.
Comments: Although P. persicae has not been recorded from the United States, it
remains a potential pest because of its range of economically important hosts (Stoet-
zel 1990). Large populations of P. persicae occurring on the bark can cause fruit not to
develop or premature fruit drop; this species produces large amounts of honeydew
and is tended by ants (Stoetzel 1994). Pterochloroides persicae is not listed as trans-
mitting a virus (Chan et al. 1991).

Rhopalosiphum nymphaeae (L. 1761)
Figs. 1, 4, 5
Synonymy:
& ** Rhopalosiphum nymphaeae (L.)
ESA approved common name: waterlily aphid
Taxonomic characters: Wingless adult female.-In life body color olive green to
golden brown, with waxy covering on head and prothorax; tibiae completely dark. Me-
dium sized, body length 2.0-2.5 mm, rounded. Antennae 6 segmented; tubercles not
well developed, terminal process approximately 3-33/ times length of base antennal
segment VI; antennal segment III-V without secondary sensoria. Cornicles dusky,
without setae, swollen with apical constriction proximal to flange, 22/-5 times as long
as wide, longer than length of cauda. Cauda dusky, elongate, nearly twice as long as
wide with 2-3 pairs of lateral setae.
Winged adult female.-In life body color similar to wingless adult female; hind
wing with 2 oblique veins; small to medium sized, body length 1.4-2.5 mm. Antennae
6 segmented, terminal process approximately 3-33/ times length of base antennal seg-
ment VI; antennal segment III with 12-22 secondary sensoria of similar size; antennal
segment IV with 0-5 secondary sensoria; antennal segment V without secondary sen-
soria. Cornicles dusky, without setae, swollen with apical constriction proximal to
flange, 43/-7 times as long as wide, longer than length of cauda. Cauda dusky, elon-
gate, nearly twice as long as wide with 2 pairs of lateral setae.
Hosts: In the spring, R. nymphaeae feeds on the young twigs, leaf petioles, and
fruit stalks of numerous species of Prunus; various species of aquatic plants serve as
secondary hosts.
U.S. distribution: Widespread.

















Florida Entomologist 81(3) September, 1998


Distribution in the world: Virtually worldwide.
Comments: Rhopalosiphum nymphaeae transmits six plant viruses, but is not
listed as a vector of a peach virus (Chan et al. 1991).

KEY TO THE WINGLESS ADULT FEMALES OF APHID SPECIES POTENTIALLY COLONIZING
ON PEACH IN THE UNITED STATES

1. Terminal process of antennal segment VI shorter than base; cornicles trun-
cated cones with numerous setae Pterochloroides persicae (Cholodkovsky)
Terminal process of antennal segment VI longer than base; cornicles vari-
ous but without setae .......................................... 2
2. Cornicles distinctly shorter than length of cauda ....................
...................... Hyalopterus pruni (Geoffroy), mealy plum aphid
Cornicles subequal or longer than length of cauda ................... 3
3(2). Antennal tubercles not well developed, not extending beyond frons or ap-
proximately even with frons (Fig. 1) .............................. 7
Antennal tubercles well developed, extending beyond frons (Fig. 1) ..... 4
4(3). Cornicles with apical region of polygonal reticulation .................
..................... Macrosiphum euphorbiae (Thomas), potato aphid
Cornicles without apical region of polygonal reticulation ............. 5
5(4). Cornicles entirely dark; abdomen with large dorsal patch ..............
...................... Myzus cerasi (F.), black cherry aphid
Cornicles pale, tips may be dark; abdomen without large dorsal patch ... 6
6(5). Terminal process >5 times length of base; cornicles constricted medially,
slightly swollen apically ..... Myzus persicae (Sulzer), green peach aphid
Terminal process <5 times length of base; cornicles slightly tapered with
slight curvature ........................... Myzus varians Davidson
7(3). Cauda stout, less than 2x longer than wide ........................ 8
Cauda elongate, nearly 2x or more longer than wide ................ 10
8(7). Terminal process >4 times length of base; cornicles >3 times as long as
wide ............ Brachycaudus persicae (Passerini), black peach aphid
Terminal process <4 times length of base; cornicles 3 times as long as wide
. . . ... . . . . . . . . . . . . . . .... . . .9
9(8). Abdomen without dark dorsal markings; cauda pale ..................
............ Brachycaudus helichrysi (Kaltenbach), peach leaf curl aphid
Abdomen with dark dorsal markings; cauda dark ....................
..... ............ .... Brachycaudus schwartzi (Borner), peach aphid
10(7). Terminal process >4 times length of base; cornicles dark and cauda pale .
.................... Hysteroneura setariae (Thomas), rusty plum aphid
Terminal process <4 times length of base; cornicles dark or dusky and cauda
dark ....................................................... 11
11(10). Cornicles swollen apically; cauda with 2-3 pairs of lateral setae .........
...................... Rhopalosiphum nymphaeae (L.), waterlily aphid
Cornicles gradually tapered; cauda with 3-5 pairs of lateral setae .......
...................... Aphis spiraecola Patch, spirea aphid


KEY TO THE WINGED ADULT FEMALES OF APHID SPECIES POTENTIALLY COLONIZING ON
PEACH IN THE UNITED STATES

1. Forewing with large distinctive dark patches; terminal process of antenna
segment VI shorter than base .... Pterochloroides persicae (Cholodkovsky)

















Stoetzel & Miller:Aphids on Peach in the US.


Forewing without large distinctive dark patches; terminal process of anten-
nal segment VI longer than base ................................. 2
2. Cornicles distinctly shorter than length of cauda ....................
..................... Hyalopterus pruni (Geoffroy), mealy plum aphid
Cornicles subequal or longer than length of cauda .................. 3
3(2). Antennal tubercles not well developed, not extending beyond frons or ap-
proximately even with frons .................................... 7
Antennal tubercles well developed, extending beyond frons ........... 4
4(3). Cornicles with apical region of polygonal reticulation .................
.................... Macrosiphum euphorbiae (Thomas), potato aphid
Cornicles without apical region of polygonal reticulation ............. 5
5(4). Terminal process >5 times length of base; cornicles with slight curvature
................... .............. Myzus varians Davidson
Terminal process <5 times length of base; cornicles tapered slightly or with
slight medial constriction, without curvature ....................... 6
6(5). Antennal segment III with 8-11 secondary sensoria of similar size and in a
straight row; cornicles with slight medial constriction ................
.................. Myzus persicae (Sulzer), green peach aphid
Antennal segment III with 12-16 secondary sensoria of similar size and in
an irregular row; cornicles tapered slightly and curved ................
............................... Myzus cerasi (F.), black cherry aphid
7(3). Cauda stout, less than 2x longer than wide ........................ 8
Cauda elongate, nearly 2x or more longer than wide ................ 10
8(7). Terminal process >4 times length of base; antennal segment V with 2-4 sec-
ondary sensoria .... Brachycaudus persicae (Passerini), black peach aphid
Terminal process <4 times length of base; antennal segment V without sec-
ondary sensoria............................................... 9
9(8). Antennal segment III with 17-23 secondary sensoria; cornicles dusky and
cauda pale ...................................................
........... Brachycaudus helichrysi (Kaltenbach), peach leaf curl aphid
Antennal segment III with 33-40 secondary sensoria; cornicles and cauda
dark .................. Brachycaudus schwartzi (Borner), peach aphid
10(7). Terminal process >5 times length of base; cornicles dark and caudal pale to
nearly white ........ Hysteroneura setariae (Thomas), rusty plum aphid
Terminal process <4 times length of base; cornicles dark or dusky and cauda
dark ....................................................... 11
11(10). Cornicles swollen apically; cauda with 2-3 pairs of lateral setae ........
..................... Rhopalosiphum nymphaeae (L.), waterlily aphid
Cornicles gradually tapered; cauda with 3-7 pairs of lateral setae .......
............................... Aphis spiraecola Patch, spirea aphid

ACKNOWLEDGMENTS

We thank S. Lingafelter (USDA-ARS, Washington, D.C.), M. Schauff (USDA-ARS,
Washington, D.C.), and A. Jensen (University of Maryland, College Park, MD) for
their helpful comments and suggestions.

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ANONYMOUS. 1994. 1992 Census of Agriculture Vol. 1 Geographic Area Series Part 51
United States Summary and State. U.S. Department of Agriculture., National
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ANONYMOUS. 1996. Agricultural Statistics 1995-1996. U.S. Department of Agricul-
ture, National Agricultural Statistic Service. 1 volume (various paging).
ASHMEAD, W. H. 1882. On the Aphididae of Florida, with descriptions of new species.
Canadian Entomol.14:88-93.
BARNETT, W. W., AND R. E. RICE. 1992. Insect and mite pests. in LaRue, J. H. and
Johnson, R. S. (eds.) 1992. Peaches, Plums, and Nectarines: Growing and Han-
dling for Fresh Market. Univ. California Coop. Ext. Pub. 3331, 246 pp.
BASKY, Z., AND L. SZALAY-MARSZO. 1987. Study of isolation mechanisms in the Hya-
lopterus pruni and Hyalopterus amygdali complex. in Holman, J., Pelikan, J.,
Dixon, A. F. G. and Weismann, L. (eds.) 1987. Population Structure, Genetics
and Taxonomy of Aphids and Thysanoptera. SPB Academic Publishing, The
Hague, pp. 370-376.
BLACKMAN, R. L., AND V. F. EASTOP. 1984. Aphids on the world's crops: An identifica-
tion and information guide. John Wiley & Sons, Ltd., Chichester, 466 pp.
BLACKMAN, R. L., AND V. F. EASTOP. 1994. Aphids on the world's trees: An identifica-
tion and information guide. CAB International, Wallingford, 1004 pp.
BLANCHARD, E. 1840. Aphidiens. Histoire Naturelle des Insectes. Orthoptres, N6urop-
tres, H6miptres, Hym6noptres, L6pidoptres et Diptres. Dum6nil, Paris 3: 1-672
BORNER, C. 1931. Mitteilungen uiber Blattlause. (Aus der Biologischen Reichsanstalt
Zweigstelle Naumburg a. S.). Anz. Schadlingskunde 7: 8-11.
CHAN, C. K., A. R. FORBES, AND D. A. RAWORTH. 1991. Aphid-transmitted viruses and
their vectors of the world. Agric. Canada Res. Branch Tech. Bull. 1991-3E, 216
pp.
CHOLODKOVSKY, N. 1899. Aphidologische Mittheilumgen. Zoologischen Anzeiger 22:
468-477.
DAVIDSON, W. M. 1912. Aphid notes from California. J. Econ. Entomol. 5: 404-413.
FABRICIUS, J. C. 1775. Rhyngota. System Entomologiae. Sistens insectorum classes,
ordines, genera, species, adiectis synonymis, locis, descriptionibus, observa-
tionibus, Korte 1775: 1-816.
GEOFFROY, E. L. 1762. Histoire abr6g6e des Insectes qui se trouvent aux environs de
Paris. Paris. Vol. 1. 523 pp.
KALTENBACH, J. H. 1843. Monographie der Familien der Pflanzenlause. Aachen, 223
pp.
LINNAEUS, C. 1761. II. Hemiptera. Aphis. Fauna Suecica sistens animalia Sueciae
regni: Mammalia, Aves, Amphibia, Pisces, Insecta, Vermes. Distributa per
classes et ordines, genera et species, cum differentiis specierum, synonymis
auctorum, nominibus incolarum, locis natalium, descriptionibus insectorum.
Editio altera, auctior 1761: 1-578.
PALMER, M. A. 1952. Aphids of the Rocky Mountains Region. Thomas Say Foundation
5: 1-452.
PASSERINI, G. 1860. Gli afidi con un prospetto dei gereri ed alcune specie nuove Ital-
lane. Parma, 40 pp.
PATCH, E. M. 1914. Maine aphids of the rose family. Maine Agric. Exp. Stn. Bull. 233:
253-280.
SMITH, C. F., AND C. S. PARRON. 1978. An annotated list of Aphididae (Homoptera) of
North America. North Carolina Agric. Exp. Stn. Tech. Bull. 255: 428 pp.
SMITH, E. F. 1890a. The black peach aphis. A new species of the genusAphis. Entomol.
Amer. 6: 101-103
SMITH, E. F. 1890b. The black peach aphis. A new species of the genusAphis. Entomol.
Amer. 6: 201-208.
STOETZEL, M. B. (chairman). 1989. Common Names of Insects & Related Organisms.
Entomological Society of America, Lanham, MD, 199 pp.
STOETZEL, M. B. 1994. Aphids (Homoptera: Aphididae) of potential importance on Cit-
rus in the United States with illustrated keys to species. Proc. Entomol. Soc.
Washington. 96: 74-90.
STOETZEL, M. B. 1990. Some aphids of importance to the southeastern United Sates
(Homoptera: Aphididae). Florida Entomol. 73: 580-586.
















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SULZER, J. H. 1776. Die Blattlaufe, pp. 98-105 in: Abgekurzte Geschichte der Insekten
nach dem Linaeischen System. 274 pp.
THOMAS, C. 1878. A list of the species of the tribe Aphidini, family Aphidae, found in
the United States, which have been heretofore named, with descriptions of
some new species. Bull.Illinois State Lab. Nat. Hist. 2: 3-16.
VAN DER GOOT, P. 1912. Uber einige wahrscheinlich neue Blattlausarten aus der
Sammlung des Naturhistorischen Museums in Hamburg. Mitteilungen aus
dem Naturhistorischen Museum in Hamburg. 29: 273-284.
















Jones & Snodgrass: Biology of Deraeocoris nebulosus


DEVELOPMENT AND FECUNDITY OF DERAEOCORIS
NEBULOSUS (HETEROPTERA: MIRIDAE) ON BEMISIA
ARGENTIFOLII (HOMOPTERA: ALEYRODIDAE)

WALKER A. JONES' AND GORDON L. SNODGRASS2
1Beneficial Insects Research Unit, Subtropical Agricultural Research Center
Agricultural Research Service, U.S. Department of Agriculture
2413 E. Hwy. 83, Weslaco, TX 78596

2Southern Insect Management Research Unit, Agricultural Research Service
U.S. Department of Agriculture, P.O. Box 346, Stoneville, MS 78596

ABSTRACT

The developmental and reproductive biology of the native predaceous mirid Der-
aeocoris nebulosus was studied in the laboratory using immatures of the whitefly Be-
misia argentifolii as prey. Nymphs were kept individually in ventilated Petri dishes
and provided with a constant supply of prey colonized on excised sweet potato leaves
rooted in hydroponic solution and kept at 27 C. Females were kept similarly and daily
egg production was recorded. There were five nymphal instars. Mean development
from first instar to adult was 13.3 d; there were no significant differences in develop-
ment rate between the sexes. After a 3-d preoviposition period, females produced
about 10-14 eggs per day for nearly 20 days before oviposition rate declined with age.
Females lived an average of 32.8 d (range 3-58 d), and mean fecundity was 242.3 eggs
per female (range 0-392).

Key Words: predator, whitefly, biological control, biology, rearing

RESUME

La biologia reproductive y el desarrollo del mirido depredador native Deraecoris
nebulosus se estudiaron en condiciones de laboratorio utilizando ninfas de la mos-
quita blanca, Bemisia argentifolii, como press. Las ninfas del mirido se mantuvieron
individualmente en cajas de Petri ventiladas y a una temperature constant de 27 C.
Las press fueron constantemente presentadas a los depredadores en hojas de camote
enraizadas en tubos de plastico conteniendo una soluci6n hidrop6nica. Las hembras
de los depredadores se mantuvieron en condiciones ambientales similares a las de las
ninfas y la producci6n de huevecillos se registry diariamente. Se detectaron 5 estadios

















Florida Entomologist 81(3) September, 1998


ninfales. El promedio del tiempo de desarrollo del primer estadio al adulto fue de 13.3
dias; no se detectaron diferencias significativas en el tiempo de desarrollo entire ma-
chos y hembras. Despues de un period pre-oviposicional de 3 dias las hembras pro-
dujeron diariamente de 10 a 14 huevecillos por casi 20 dias continues, disminuyendo
despues debido a la edad. El promedio de longevidad de las hembras fue de 32.8 dias
con una fluctuaci6n de 3 a 58 dias y el promedio de fecundidad por hembra fue de
242.3 huevecillos con una fluctuaci6n de 0 a 392 huevecillos.





The dramatic increase in the economic importance of the Bemisia tabaci (Genna-
dius) species complex has been attributed to the virtual replacement of the sweetpo-
tato whitefly, B. tabaci (= biotype A), with a new species, the silverleaf whitefly, B.
argentifolii Bellows & Perring (= sweetpotato whitefly B. tabaci, biotype B). The ap-
pearance of this new pest has generated widespread activity aimed at developing
management methods that minimize additional pesticide load in the environment.
Manipulative biological control methods are being investigated for application in
greenhouse and field crops. Certain predaceous Miridae might have potential for
managing pest whiteflies, particularly in affected greenhouse crops (e.g. Malausa et
al. 1987, Alomar et al. 1990, Fransen 1994). Research has been conducted in Europe
on various biological aspects of predaceous mirids in the genera Cyrtopeltis, Dicyphus,
and Macrolophus (e.g. Fauvel et al. 1987, Malausa 1989, Fransen 1994). Macrolophus
caliginosus Wagner is currently sold commercially for whitefly control (van Schelt et
al. 1996. Hunter 1997). Deraeocoris spp. have also been recognized as efficient preda-
tors of whiteflies, and their potential has recently been evaluated against B. tabaci
(Susman 1988, Kapadia & Puri 1991). The North American species D. brevis (Uhler)
is sold commercially for whitefly management (Hunter 1997).
Deraeocoris nebulosus (Uhler) occurs throughout most of the United States and
Canada (Carvalho 1957, Henry & Wheeler 1988). Its value as a predator was recog-
nized over a century ago (Uhler 1876, Howard 1895). Field populations ofD. nebulo-
sus can be high. This predator was observed in commercial cotton fields in association
with aphids in west-central Mississippi, even under heavy insecticide use (Snodgrass
1991) and has been associated with whitefly infestations in cotton there in recent
years (G.L.S., unpublished). Aspects of the biology of D. nebulosus have been studied
previously with the oak lace bug Corythucha arcuata (Say) (Wheeler et al. 1975) and
the cotton aphidAphis gossypii Glover (Snodgrass 1991) as prey. Wheeler et al. (1975)
critically reviewed the literature concerning D. nebulosus and summarized the vari-
ous host and habitat associations of this well-known predator; whiteflies (Aley-
rodidae) and other sessile Homoptera are prominently mentioned. The goals of the
present study were to determine if B. argentifolii is a suitable prey for development
and reproduction ofD. nebulosus, and to provide basic information for further inves-
tigations on the potential of this predator as a management tool against the Bemisia
spp. complex and other whiteflies.

MATERIALS AND METHODS

Insects were colonized from several dozen nymphs and adults collected in cotton
near Stoneville, Washington County, in west-central Mississippi in August 1996. The
duration of each immature stage was measured on F, progeny from the field-collected
insects. Fecundity was derived for females from the development rate observations. To
obtain eggs, about 10 unsexed adults from the initial field collection were placed to-

















Jones & Snodgrass: Biology of Deraeocoris nebulosus 347

gether in each of several 120mm x 25 mm ventilated plastic culture dishes. Each dish
contained a whitefly-infested sweet potato leaf. Leaves had previously been excised
and placed individually in floral aquapics where they readily rooted in hydroponic so-
lution (Aqua-Ponics International, Los Angeles, CA 90041). Prior observations indi-
cated that eggs are deposited primarily in the leaf petioles and main leaf veins. First
instar nymphs were obtained on the day of eclosion by daily examination of each leaf
assembly containing eggs. Because preliminary observations also suggested that
nymphs sometimes prey on each other when confined, these studies used isolated in-
dividuals. Thirty, newly emerged, nymphs were placed individually in a 120mm x 25
mm ventilated plastic culture dish with a rooted sweet potato leaf containing about
250 B. argentifolii nymphs of various ages. All tests were conducted at 27 + 2 C, 55
10% RH, and a photoperiod of 16:8 (L:D). Test insects were examined daily for change
to the next instar or stage. Leaves with host nymphs were changed every 3-4 days.
The sex of each insect was determined when it reached the adult stage.
Fecundity was measured by placing individual, general females with one or two
males of mixed age, in dishes with infested leaves as described above. Males were not
replaced after death. Leaves were examined daily for eggs. Eggs deposited over each
24-hr period were marked with colored ink so that one day's egg production could be
distinguished from the next. Viability was not determined. Leaves were kept with
each female for 3-4 days before replacement. A continuous series of infested leaves
was kept with each female until her death. Some qualitative behavioral observations
on mating, oviposition, and foraging were also made.
Developmental data were analyzed by ANOVA, and compared by sex using a t-
test. Mean developmental time per instar and sex were subjected to Tukey's HSD test
(P < 0.05) (SYSTAT, Inc. 1992).

RESULTS AND DISCUSSION

Eggs were usually found embedded in plant tissue with only the long hairlike mi-
cropylar process protruding as described by McCaffrey & Horsburgh (1980); the cap
was usually visible through the oviposition slit. Occasionally, eggs protruded from the
plant surface or were not embedded at all. Unembedded eggs were not observed for
eclosion. Although not specifically recorded, eggs sometimes were observed to be de-
posited in small groups. Generally, more eggs were deposited in the leaf petiole than
in the leaf veins. McCaffrey & Horsburgh (1980) previously reported that eggs of D.
nebulosus were deposited in leaf mid-veins of apple, but not in petioles or twigs. Other
predaceous mirids have been reported to deposit their eggs in major leaf veins and
leaf petioles (Cobben 1968, Khristova et al. 1975, Ferran et al. 1996).
There were five nymphal stages, as previously reported by Wheeler et al. (1975).
Kapadia & Puri (1991) reported that a Deraeocoris sp. in India had six nymphal
stages. Twenty-four of 30 nymphs reached adult, 16 males and only 8 females; at least
two deaths were due to injury during handling. Total time from egg eclosion to adult
at 27 C averaged 13.3 d (Table 1). There was no significant difference in development
rate by sex (df = 22; P = 0.69). Wheeler et al. (1975) reported development ofD. nebu-
losus to take 19.8-d at 21-22 C; Westigard (1973) recorded D. brevis piceatus Knight
to have a mean development time of 25 days at 21 C. Susman (1988) reported the
nymphal duration ofD.pallens Reuter to be 11.1 days at 25-28 C. Differences among
reported development rates is at least partially a function of the different tempera-
tures and species used.
Mean egg deposition per female was 1.5 on day four, then ranged between 9.5-13.9
eggs per day until day 22, whereupon egg production began to decrease with increas-
ing age (Fig. 1). Daily egg production was calculated on the basis of the number of fe-



















348 Florida Entomologist 81(3) September, 1998

TABLE 1. DEVELOPMENT TIME FOR EACH INSTAR OF DERAEOCORIS NEBULOSUS NYMPHS
FED NYMPHS OF BEMISIA ARGENTIFOLII.

Mean Development time (days SE)


Male

2.5 0.18
2.0 0.12
2.3 0.14
2.2 0.10
4.4 0.24
13.3 0.30


Female

2.8 0.25
2.0 0.19
2.1 0.35
2.8 0.25
3.5 0.19
13.1 0.30


Male + Female

2.6 0.15
2.0 0.10
2.2 0.15
2.4 0.12
4.1 0.19
13.3 0.22


males surviving for a given day. One individual lived 58 days, depositing its last eggs
at day 57. Mean fecundity was 242.3 eggs per female, ranging from 0-392. No D. neb-
ulosus deposited eggs before the third day as an adult. Fecundity and female longevity
were greater than that previously reported for any other predaceous mirid. Fecundity
in D. nebulosus has not previously been reported. The oviposition period of an Indian
species of Deraeocoris fed with B. tabaci averaged 11.3 days, with females living an
average of 13.4 days at about 24 C (Kapadia & Puri 1991); D. pallens females depos-
ited 23-268 eggs per female over an average lifespan of 14-34 days when fed with B.



2011


- Mean Eggs per Day
"." Percent Females alive


- 75



-50
IL



- 25


Fig. 1. Mean daily egg production per female (solid line), and daily survival (dotted
line) of female D. nebulosus.


Instar


IV
V
Total


15-




0
V 10
(A
CD




0"
5-





0- ^
9

















Jones & Snodgrass: Biology of Deraeocoris nebulosus 349

tabaci (Susman 1988). The commercially available predator M. caliginosus, when fed
whitefly immatures, had a preoviposition period of 4 days at 23 C, and began oviposi-
tion at two eggs per day, which increased to over seven eggs per day for the rest of a
15-d study on fecundity (van Schelt et al. 1996).
Qualitative observations suggested that most foraging may not take place during
daytime hours. Nymphs and especially adults were usually found resting under
leaves or under the filter paper. When maintained in the greenhouse, these insects
were primarily found within leaf litter of potted plants. Nevertheless, it was difficult
keeping enough whitefly immatures to maintain the colony. Mating and oviposition
was rarely witnessed.
Our preliminary observations showed that nymphs probably prey on each other
when confined. Thus, the possibility of production for release against whiteflies may
require special rearing conditions that minimize cannibalism.
These results demonstrate that D. nebulosus can survive, develop, and reproduce
normally using B. argentifolii immatures as prey, and that the fecundity of this pred-
ator is greater than that of other predaceous mirids previously tested on any host.
There is no evidence that this species is also partially phytophagous, as is the case
with certain other predaceous mirids studied for their potential in managing white-
flies. Further studies are warranted to measure the efficacy ofD. nebulosus against
Bemisia spp., as well as other pests that are potential prey of this mirid.

ACKNOWLEDGMENTS
We greatly appreciate the assistance and perseverance of Patty Silva in helping to
maintain the insects and record data and to Reyes Garcia III for statistical analysis
and graphics.

REFERENCES CITED

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COBBEN, R. H. 1968. Evolutionary trends in Heteroptera. Part I.: Eggs, architecture
of the shell, gross embryology and eclosion. Centre for Agricultural Publishing
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FAUVEL, G., J. C. MALAUSA, AND B. KASPAR. 1987. Etude en laboratoire des princi-
pales caracteristiques biologiques de Macrolophus caliginosus (Heteroptera:
Miridae). Entomophaga 32: 529-543.
FERRAN, A., A. RORTAIS, J. C. MALAUSA, J. GAMBIER, AND M. LAMBIN. 1996. Oviposi-
tional behaviour of Macrolophus caliginosus (Heteroptera: Miridae) on tobacco
leaves. Bull. Entomol. Res. 86: 123-128.
FRANSEN, J. J. 1994. Bemisia tabaci in the Netherlands; Here to stay? Pesticide Sci-
ence 42: 129-134.
HENRY, T. J., AND A. G. WHEELER, JR 1988. Family Miridae Hahn, 1833, pp. 251-507.
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HOWARD, L. O. 1895. Some scale insects of the orchard, pp. 249-276. In: Yearbook
USDA, 1894.
HUNTER, C. D. 1997. Suppliers of beneficial organisms in North America. California
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KAPADIA, M. N., AND S. N. PURI. 1991. Biology and comparative predation efficacy of
three heteropteran species recorded as predators of Bemisia tabaci in Maha-
rashtra. Entomophaga 36: 555-559.

















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daceous bug Macrolophus caliginosus Wagner (Heteroptera: Miridae) on glass-
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MALAUSA, J.-C. 1989. Lutte int6gr6e sous serre: Les punaises pr6datrices mirides
dans les cultures de Solanac6es du sud-est de la France. Rev. Hort. 298: 39-43.
MCCAFFREY, J. P., AND R. L. HORSBURGH. 1980. The egg and oviposition site of Der-
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SNODGRASS, G. L. 1991. Deraecoris (sic) nebulosus (Heteroptera: Miridae): little
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SUSMAN, I. 1988. The cotton insects of Israel and aspects of the biology of Deraeocoris
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Vanderbilt et al.: R. cruentatus Mating Behavior


MATING BEHAVIOR AND SEXUAL RESPONSE TO
AGGREGATION PHEROMONE OF RHYNCHOPHORUS
CRUENTATUS (COLEOPTERA: CURCULIONIDAE)

CLAUDIA F. VANDERBILT, ROBIN M. GIBLIN-DAVIS' AND THOMAS J. WEISSLING
Fort Lauderdale Research and Education Center, University of Florida, IFAS
3205 College Avenue, Fort Lauderdale, FL 33314

'To whom correspondence should be addressed

ABSTRACT

Mating behavior ofRhynchophorus cruentatus (Fabricius) was investigated in the
laboratory. The sequence of behaviors was consistent for all weevils that mated. Males
exhibited rostral rubbing and antennal tapping before copulation, guarding females
afterwards. Mating frequency and celerity were compared between sequestered male-
female pairs and for focal males in simulated aggregations. Field-collected and virgin
males in groups were significantly quicker to initiate mating behavior and attempted
to mate more often per session than males in sequestered pairs. Increased sexual
stimulation in weevil aggregations appears to be semiochemically-mediated. Visual
and tactile cues were eliminated as contributing stimuli in simulated aggregation
arenas. Males were significantly more stimulated to mate in the presence of synthetic
aggregation pheromone, 5-methyl-4-octanol (cruentol) than in its absence.

Key words: aggregation, mating behavior, pheromone, Rhynchophorus cruentatus, 5-
methyl-4-octanol

RESUME

El comportamiento de apareo de Rhynchophorus cruentatus (Fabricius) fue inves-
tigado en el laboratorio. La secuencia de comportamientos fue la misma para todos los
gorgojos que se aparearon. Los machos exhibieron frotamiento con el rostro y golpeci-
tos con las antenas antes de la copulaci6n, la que fue seguida por la guardia de las
hembras. La frecuencia y rapidez del apareo fueron comparados entire parejas aisla-
das de macho y hembra y machos focales en agregaciones artificiales. Se observe que
los machos colectados en el campo y los machos virgenes en agregaciones iniciaban el
comportamiento de apareo significativamente mas rdpido y que intentaban aparearse
mas seguido en cada sesi6n que los machos de parejas aisladas. El incremento de la
estimulaci6n sexual en agregaciones de gorgojos parece estar mediado por un com-
puesto semioquimico. Fueron eliminados los estimulos visuales y tactiles como contri-
buyentes al apareo dentro de arenas con agregaciones artificiales de gorgojos. Los
machos fueron significativamente mas estimulados para aparearse en la presencia de
la feromona sintetica de agregaci6n 5-metil-4-octanol (cruentol) que en su ausencia.




The palmetto weevil, Rhynchophorus cruentatus (F.), is the largest weevil (24-33
mm long) in the continental United States (Woodruff 1967). This weevil is sympatric
with the native cabbage palmetto, Sabal palmetto (Walter) (Woodruff 1967) from the
Florida Keys through the coastal regions of South Carolina and Texas (Wattanapong-
siri 1966). In most cases, R. cruentatus is not considered to be a primary pest of cab-
bage palmetto, but a secondary pest that attacks transplanted or otherwise stressed

















Florida Entomologist 81(3) September, 1998


palms in the landscape (Giblin-Davis & Howard 1989). Recent research suggests that
it can be a serious pest of field-grown Phoenix canariensis (L.) (unpublished data). The
weevil is attracted to the fermenting plant volatiles from chopped palm tissue and
chopped sugarcane, Saccharum officinarum (Weissling et al. 1993). There is a syner-
gistic effect when these plant volatiles are combined with S,S-5-methyl-4-octanol
(cruentol), the aggregation pheromone produced by R. cruentatus males (Weissling et
al. 1994a; Perez et al. 1994). Large aggregations of male and female R. cruentatus are
attracted to this combination, presumably for mating and oviposition purposes (Gib-
lin-Davis et al. 1994; Weissling et al. 1993).
Many species of insects and other animals are known to aggregate for mating pur-
poses (Landolt 1997). Evolutionary biologists have investigated advantages for males
calling in conspecifics (which invites competition from other males) (Thornhill & Al-
cock 1984) and the advantages of multiple mating for females (Sakurai 1996; Lewin
1988). The production of aggregation pheromones may serve to recruit widely distrib-
uted conspecifics to rare resources (i.e. stressed hosts). Therefore, it may be advanta-
geous to males to call females as a way to reduce the amount of time spent searching
for widely dispersed potential mates. This may also be an adaptation that enables R.
cruentatus to cope with the seasonal emergence patterns characteristic of this species
(Weissling et al. 1994b), and to overwhelm the defenses of a potential palm host (Gib-
lin-Davis et al. 1996).
Rhynchophorus cruentatus males are morphologically well adapted to mating in
aggregations. On the tibiae of the forelegs, males possess a row of setae, commonly re-
ferred to as a "sex comb". A similar structure is used by males of some other species
of insects to facilitate grasping and control of females (Spieth 1952). This structure
may also prevent aggregated males from dislodging copulating males. Another possi-
ble function for the tibial hairs may be to distribute pheromone. Males of R. pal-
marum (L.) apparently produce pheromone in the prothoraxic glands and pass the
molecules forward to the rostrum where it is distributed by setae (Sanchez et al.
1996). Rhynchophorus cruentatus is the only species of Rhynchophorus that lacks
these rostral setae but instead possesses rostral ferrugae (Wattanapongsiri 1966).
Possibly they wipe the rostrum with the tibial hairs to help distribute pheromone. Be-
cause little is known about the mating behavior of the agriculturally important Rhyn-
chophorinae we endeavored to characterize the mating behavior of R. cruentatus in
the laboratory.


MATERIALS AND METHODS

Adult weevils were collected in Hendry and Dade Counties, Florida during the
peak trapping seasons of 4/96-7/96 and 4/97-7/97. In Hendry County, 120 weevils were
collected in four live traps set in a field with cabbage palmettos from which the buds
had been removed by "palm heart" collectors. In Dade County, weevils were trapped
from a grove of P. canariensis that had sustained severe damage from R. cruentatus.
Fifty-five virgin weevils (harvested directly from cocoons) and 140 adults with un-
known mating histories were collected. The trap design used was previously described
by Weissling et al. (1992). Each trap was baited with sugarcane (400 g), ethyl acetate
(6 ml) in open-topped vials and one controlled-release dispersal unit containing syn-
thetic racemic cruentol; 5-methyl-4-octanol (96% pure). Cruentol was obtained from
Dr. A. C. Oehlschlager (ChemTica, San Jose, Costa Rica) (release rate @ 25 C = 3 mg/
d). Once collected, weevils were maintained in covered disposable polyethylene con-
tainers with sugarcane and separated by sex for no less than 18 h prior to each mating
session. Adult insects for bioassay were sexed using dimorphic rostral and tibial char-

















Vanderbilt et al.: R. cruentatus Mating Behavior


acteristics (Wattanapongsiri 1966). Rhynchophorus cruentatus is a relatively rare in-
sect (Weissling et al. 1994a) and it was necessary to reuse the same weevils in
repeated trials, except in the trials involving virgins. Insects were selected arbitrarily
from containers for use. Weevils smaller than 29 mm were not used for male-female
pairs and size assertive mating was not examined.
Mating was defined as the attempted insertion of the aedeagus of one male weevil
while in contact with another female or male weevil. No assumptions were made
about spermatophore transfer. Mating behaviors were observed by placing weevils in
polystyrene arenas (Tri-State Plastics, Dixon, KY) (21 cm diam x 8 cm high) for 30
min sessions. Experiments were conducted under ambient fluorescent lighting (0.74
klux) at 22-26C and 44-60% RH. In all experiments, two sexual stimulation indica-
tors for males were measured: 1) the frequency of mating per 30 min session and 2)
the time from placement into the arena until mating was initiated.


Experiment 1. Field-collected Weevils: Description of the Mating Sequence of Seques-
tered Pairs; Observation of Behaviors in Simulated Aggregations and Comparison of
Sexual Stimulation Factors for Sequestered Versus Artificially Aggregated Males

A. Ethogram. Preliminary examination of weevil pairs allowed for the preparation
of an ethogram. This preparatory ethogram was quantified using observations of the
complete mating sequence of the 20 sequestered males in experiment 1C.
B. Observation of behavior in aggregations. Initially, 10 trials of scan sampling
were conducted and some general observations were made about mating tendencies
in aggregations. An ethogram of behaviors in the group environment was not pre-
pared because the pace of activity in these arenas was so frenetic that quantification
of any single behavior was impossible.
C. Comparison of the two sexual stimulation indicators for sequestered versus arti-
ficially aggregated males. Comparisons were made for the frequency of mating and
the time to begin mating between 20 sequestered males and 20 focal males in an ar-
tificial mating aggregation. The artificial aggregation was assembled by simulta-
neously placing one randomly selected male weevil that was marked with a small
amount of metallic marker (Sanford silver coat, Bellwood, IL) on the pronotum, with
nine other males and 10 females into an arena. Male sexual stimulation indicators
were then compared between sequestered and artificially aggregated males as previ-
ously described.

Experiment 2. Virgin Weevils: Comparison of Sexual Stimulation Indicators for Se-
questered Versus Artificially Aggregated Males

Experiment 1C was repeated with virgin weevils. Twenty replications with se-
questered virgin male-female pairs were compared to marked focal virgin males in ar-
tificial aggregations, 15 replicates.
In order to isolate the factors responsible for male sexual stimulation in groups,
experiments 3, 4, 5 and 6 were conducted using the same containers in a different ar-
rangement. A mating arena consisted of two containers stacked one on top of the
other, open sides together, with a barrier separating them (Fig. 1). The lower chamber
contained the treatment and the mating pair under observation was placed in the up-
per chamber, moving about on the barrier. This created a fractional aggregation. Bar-
rier components and upper chambers were washed with soap and water and dried
after each repetition. Arena placement was randomized for each replicate of the fol-
lowing experiments.

















Florida Entomologist 81(3) September, 1998


Observed
-- ~ aipair
Perforated
-.. aluminum
barrier
Simulated
aggregation

Fig. 1. Schematic diagram of the fractionally aggregated mating arena used in ex-
periments 3 and 4. In experiment 5 only, glass barriers replaced the perforated alu-
minum. In experiment 6, synthetic aggregation pheromone replaced the weevils in
the lower chamber.



Experiment 3. Comparison of Sexual Stimulation Indicators for Sequestered Versus
Fractionally Aggregated Males

This experiment involved two treatments and tested whether semiochemical, tac-
tile or visual cues influenced the frequency and celerity of mating for upper-chamber
males. A barrier assembly consisted of a sheet of pierced aluminum (1.5 mm thick, 2
mm diam perforations, 12 holes/cm2) overlaid with black polyester open-weave stretch
fabric. The design of this arena allowed for the diffusion of volatiles into the observa-
tion chamber, while preventing the mating pair from seeing or touching weevils below.
Chambers were allowed to equilibrate for 30 min immediately prior to each trial. The
fractionally aggregated arena (treatment 1) held nine females and nine males in the
lower chamber, with the mating pair under observation in the upper chamber, simu-
lating the original group of 20 total weevils in experiment 1C. The lower chamber of
the control arena (treatment 2) was left unoccupied. There were 20 replications of
each treatment.


Experiment 4. Comparison of Sexual Stimulation Indicators for Fractionally Aggre-
gated Males by Sex of Semiochemical Source

Three fractional aggregation arenas were arranged as described for experiment 3
to test whether semiochemicals from males, females or both were important in stim-
ulating the mating behavior of the male in the chamber above. The treatments were:
nine males plus nine females, 18 females, and 18 males. There were 20 replications of
each of the three treatments.


Experiment 5. Comparison of Sexual Stimulation Indicators for Fractionally Aggre-
gated Males by Sight and Sound of Other Weevils

To test whether the sight of or vibrations from other weevils were important stim-
uli, sheets of glass (3.5 mm thick) were used as barriers in place of the fabric and alu-
minum used in experiments 3 and 4. The glass prevented volatiles from the treatment
chamber below from entering the upper chamber. Treatment 1 consisted of a clear
glass barrier with nine male plus nine female weevils below creating a situation

















Vanderbilt et al.: R. cruentatus Mating Behavior


where the pair could see and feel vibrations from the lower group but not sense semi-
ochemicals produced by the group. Treatment 2 utilized clear glass with a vacant
lower chamber exposing the weevil pair to no group-produced stimuli. Treatment 3
used the 18-weevil arrangement of treatment 1, but with painted glass as the barrier,
allowing only vibrational cues to be received. This glass sheet was sprayed with matte
black enamel (Rust-oleum Corp., Vernon Hills, IL) on the side facing the lower cham-
ber 3 wks prior to use to allow the surface to fully dry and ventilate.


Experiment 6. Comparison of Sexual Stimulation Indicators for Pheromone in Frac-
tionally Aggregated Chambers

The effects of synthetic aggregation pheromone on mating behavior of weevils
were examined. There were three treatments: two doses of (+) cruentol and a control
(no cruentol). The aluminum-fabric barriers were used in each mating arena. One-Pl
capillary glass tubes (Drummond Scientific Co., Broomall, PA) were filled with cruen-
tol and then secured upright in Seal-ease tube sealer and holder (Becton Dickenson &
Co., Rutherford, NJ). An equal amount of the Seal-ease was placed in the lower cham-
ber of the control arena. The cruentol-containing arenas held either one or five micro-
caps (release rate = 3.02 + 0.92 SD ng/h/tcap). The release rate was calculated by
placing ten 1 il microcapillary tubes in Seal-ease in the lower chamber of an arena
with an aluminum-fabric barrier and upper chamber cover. After 24 h, the amount of
cruentol lost from each tube was measured to determine the mean release rate.
Cruentol was handled with disposable gloves and stored in a -10 C freezer when not
in use. Weevils and cruentol were introduced into the testing room in separate, tightly
closed containers. Arenas were randomized and placed 2 m apart. Cruentol was intro-
duced into the lower chambers of arenas and was allowed to equilibrate for 3 min im-
mediately prior to introduction of weevils into the upper chamber. After each
replicate, lower chambers were quickly covered with lids to minimize diffusion of
cruentol into the room. There were 20 replicates of each experiment.


Statistics

A preliminary scatterplot of the time to begin mating in experiment 1 suggested
that mating in the first 250 sec was optimal for measuring sexual stimulation between
sequestered and aggregated males. Therefore, the number of males mating within the
first 250 sec was used for analysis by the Kruskal-Wallis (chi-square approximation)
test (SAS Institute 1985). The number of apparent matings per 30 min observation pe-
riod were square root transformed (x + 0.5) and analyzed by analysis of variance using
PROC ANOVA (SAS Institute 1985). Least significant difference tests (SAS Institute
1985) were used for means separation where significant differences occurred.


RESULTS AND DISCUSSION

Experiment 1. Field-collected Weevils: Description of the Mating Sequence for Se-
questered Pairs; Observation of Behaviors in Artificial Aggregations and Comparison
of Sexual Stimulation Factors for Sequestered Versus Artificially Aggregated Males

A. Ethogram. Of the 20 sequestered pairs studied for sequence of mating events,
14 mated as previously defined. All males and females made numerous physical con-
tacts with one another whether or not they later mated. A summary of the sequence

















Florida Entomologist 81(3) September, 1998


of mating events is presented in the ethogram in Fig. 2. All males engaged in rostral
rubbing, defined as touching the female's elytra with the distal tip of the rostrum and
moving it in a serpentine pattern from the pygidium forward. A similar behavior has
been observed in Ips beetles by Birch (1978) who suggested that this is a placating
gesture. Another possible explanation for this behavior is that the weevils are dis-
criminating heterospecific cuticular hydrocarbons (Takahasi & Gassa 1995). Five of
the 20 male weevils did not engage in any behaviors other than the general physical
contact and rostral rubbing (Fig. 2). The sixth male that did not mate moved directly
from rostral rubbing to guarding, described below. Of the males that did mate, all fol-
lowed a stereotyped sequence of behaviors. Both during and subsequent to the rostral
rubbing the male tapped his antennae on the elytra and pronotum of the female as he
began to mount her (Fig. 2). This antennal tapping and the actual mounting of the fe-
male was the first indication that a copulatory event was about to take place. There
were not any other discernible behaviors that could be identified as "courtship". The
antennal tapping was immediately followed by attempts to insert the aedeagus (Fig.
2). In all cases, the female remained very still during mating (Fig. 2). After a period
of time (approximately 2 min) she initiated the termination of mating by moving her
legs and walking across the arena floor. All of the males that mated maintained close
physical proximity to the female, referred to here as guarding (Fig. 2). In most cases,
the male was able to grasp the female with all six of his legs, remaining on top and
riding on her back as she moved about the arena. If he grasped with only two or four
of his legs he was dragged around with his pygidium scraping the arena floor. The
guarding behavior might serve to deter mating attempts by other males in an aggre-
gation, to stimulate the female to oviposit more quickly or to reduce the likelihood
that the female will accept another partner (Eberhard 1996). Ten of the 14 males that
mated proceeded from guarding the female to a second copulatory event (Fig. 2).
There was not always the same level of female cooperation in subsequent attempts. Of
the 10 males which went on to attempt a second mating, six attempted a third time
and two of these attempted a fourth time. The sequence of virgin mating behaviors ob-
served in experiment 2 was as illustrated in the ethogram (Fig. 2), except that some
of the virgins did not guard their female partners or they separated immediately after
mating, returning after several seconds to guard her.
B. Observation of behavior in aggregations. Male weevils seemed to be stimulated
to mate while in a mixed-gender group. This phenomenon was originally noticed when
weevils were being transported from collection sites, before they had been separated
according to sex. These original observations led us to hypothesize that males were
more highly stimulated to mate in aggregations.
In artificial aggregations, weevils engaged in frequent and apparently deliberate
physical contact irrespective of gender. Males scrambled to obtain females quickly
and there was a frenetic quality to the activities. Both males and females multiply




Ih H1 I .... 0.1 _




Fig. 2. Ethogram of Rhynchophorus cruentatus mating behavior from experiment
1A. Values represent percentage of mating pairs that proceeded to the next activity, as
indicated by arrows.




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