Title: Florida Entomologist
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00098813/00193
 Material Information
Title: Florida Entomologist
Physical Description: Serial
Creator: Florida Entomological Society
Publisher: Florida Entomological Society
Place of Publication: Winter Haven, Fla.
Publication Date: 1959
Copyright Date: 1917
Subject: Florida Entomological Society
Entomology -- Periodicals
Insects -- Florida
Insects -- Florida -- Periodicals
Insects -- Periodicals
General Note: Eigenfactor: Florida Entomologist: http://www.bioone.org/doi/full/10.1653/024.092.0401
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Bibliographic ID: UF00098813
Volume ID: VID00193
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: Open Access

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Volume 42, No. 2 June, 1959


Provost, Maurice W., and Nina Branch-Food of Chirono-
mid Larvae in Polk County Lakes...-.................----- ......--- 49

Bidlingmayer, W. L.-Mosquito Penetration Tests with
Louver Screening ------...........-----...... ......-----.--.-- .....---- 63

Labrecque, G. C., H. G. Wilson, M. C. Bowman, and J. B.
Gahan-Studies on the Development of Resistance to
DDT and Malathion in House Flies.......................---------- 69

Brown, W. L., Jr.-Synonymy in the Ant Genus Macromischa
Roger ... .--. ........----........---...~..... ...--.... --------- 73

Gurney, Ashley B.-New Records of Orthoptera and Dermap-
tera from the United States -------------------------- 75

Harris, Emmett D., Jr.-Observations on the Occurrence of a
Milky Disease Among Larvae of the Northern Masked
Chafer, Cyclocephala borealis Arrow.......................----------- 81

Griffiths, J. T.-Results from the Use of Zineb in Citrus
Groves During the 1957 and 1958 Growing Seasons..-..... 85

Book Reviews ..---- ---....................--.....-------................. 92

Published by The Florida Entomological Society


OFFICERS FOR 1958-1959

President.........------------......................-........ William P. Hunter
Vice-President --........--...--...- ...................-. Andrew J. Rogers
Secretary .....-.----..--------.------.... Lawrence A. Hetrick
Treasurer....... ...------------.---- -- Robert E. Waites
Henry True
Other Members of Executive Committee John E. Porter
Irwin H. Gilbert

LEWIS BERNER--...--......-- ..-- --....................-.....-Editor
NORMAN C. HAYSLIP ....---........---.. Associate Editor
ROBERT E. WAITES--......--------....Business Manager

THE FLORIDA ENTOMOLOGIST is issued quarterly-March, June, Septem-
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Authors are urged to consult a style manual when preparing manuscripts.
For form of literature citations, see recent issues of THE FLORIDA EN-
TOMOLIGIST. Further, authors are referred to "Suggestions for the prepara-
tion of papers submitted for publication in THE FLORIDA ENTOMOLOGIST."
FLA. ENT. 41(4): 193-194. 1958.
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The lakes of the Winter Haven area of Polk County, Florida, produce
Chironomidae (= Tendipedidae), locally called "blind mosquitoes", in
large numbers. Glyptotendipes paripes predominates, and Tendipes decorus
is the most common of the lesser species. In the summer of 1956 a pre-
liminary survey was made to determine whether nutrient effluents were the
cause of eruptions of chironomid populations. Limnological and entomolog-
ical assessments were made concurrently on thirteen lakes. Larval stomachs
of G. paripes and T. decorus were studied for comparisons of food with the
lake planktons. Larvae collected in January 1957 were then used for sea-
sonal comparisons, although the plankton was not sampled at that time
for lack of personnel.
The summer field work was done by two men: E. H. McConkey of the
State Board of Health's Bureau of Entomology did the limnological work
and Harry J. Hutton of the Polk County Arthropod Control Program did
the larval sampling and lake bottom survey. Assistance in the ion measure-
ments was rendered by the Bureau of Laboratories of the State Board of
Health while the Bureau of Sanitary Engineering advised on B.O.D. and
02 measurements. Plankton determinations and counts, in water samples
and in stomachs, were made by the junior author. The winter larval col-
lections were made, again, by Harry J. Hutton.

Since it was desirable to learn the role of pollution in chironomid pro-
duction, the study lakes were selected as follows: Undisturbed, Lakes
Thomas (Auburndale) and "X" (Lake Wales); "Industrial", with canning
plants only significant nutrient source, Lakes Tracy (Haines City) and
Conine (Winter Haven); "Citrus", grove fertilizer runoff only significant
nutrient source, Lakes Tennessee (Auburndale) and "Y" (Lake Wales);
"Septic-tank", with non-sewered homes only possible nutrient source, Lakes
Deer (Winter Haven) and Lena (Auburndale); "Sewage-plant", receiving
effluents from sewage-treatment plants, Lakes Gibson (Lakeland) and
Effie (Lake Wales); "Chain-o-lakes", interconnected lakes with sewage-
treatment plant, canning plants, septic tanks, and fertilizer run-off all as
possible nutrient sources, Lakes Cannon, May, and Lulu (Winter Haven).
Morphometric, limnological, and chironomid surveys were made on these 13
lakes in the summer of 1956.
The lakes varied from 3 to 635 acres in size and 4 to 22 feet in maximum
depth. They were mostly quite turbid, with Secchi disc visibilities running
from 6 inches to 4 feet in all but the two undisturbed lakes where they
were 5 to 12 feet. Water temperatures (summer) ranged from 26.50 C to
32.00 with little change from surface to bottom. The pH readings ranged
from 4.4 to 9.5, the two undisturbed lakes being quite acid (4.4-5.0) and
the 11 disturbed lakes being circumneutral to basic. Alkalinity was low in
the undisturbed lakes (6-9 p.p.m.) and medium (max. 197 p.p.m.) in the
disturbed lakes. Dissolved oxygen one foot off the bottom ranged from zero

1Contribution No. 63 of the Florida State Board of Health, Entomologi-
cal Research Center, Vero Beach.

50 The Florida Entomologist Vol. 42, No. 2

to 14.1 p.p.m. and from 0 to 191% saturation, the supersaturations associ-
ated usually with algal blooms. The biological oxygen demand (B.O.D.)
ranged as a means from 0.4 p.p.m. in the undisturbed lakes to 11.4 (7.6-19.0)
p.p.m. in the lakes with sewage-treatment plants. Potassium ranged from
0.4 to 0.8 p.p.m. in the undisturbed lakes and from 1.4 to 4.9 p.p.m. in the
disturbed lakes. Phosphates ran from 0 to 2.0 p.p.m. and ammonia from
0.05 to 0.57 p.p.m. Nitrates ranged from 0.22 to 8.86 p.p.m.
Temperatures in both disturbed and undisturbed lakes were only slightly
higher than those recorded for an undisturbed lake and pond in the Welaka
area by Pierce (1947). In all chemical characteristics, Os, pH, alkalinity,
and dissolved ions, the undisturbed lakes closely resembled Pierce's waters
while the disturbed lakes were higher on virtually all counts. The high
potassium levels of the disturbed lakes may be the result of commercial
fertilizer washing in as well as increments from sewage plant effluent.
Barrett (1957) showed that this ion is not used by plankton much beyond
the naturally occurring levels (usually < 1 p.p.m.), therefore its artificial
excess in disturbed lakes should give an indication of the artificial load
of phosphates and nitrates introduced simultaneously but possibly con-
sumed by plankton.
The artificial introduction of nutrient ions apparently resulted in a
great increase in pH and in plankton, especially Myxophyceae (Brannon,
1945), and the plankton in turn increased the dissolved oxygen. The sum
total of morphometrical and physical measurements is a fairly representa-
tive picture of central Florida lakes, all of which are essentially eutrophic.
The differences in chemical measurements between the undisturbed and
disturbed lakes reflect the eutrophication speed-up which is expected with
increases in nutrient inflow (Hasler, 1947; Sawyer, 1947; Edmonton et al,

Fifty-two limnological stations were established on the thirteen lakes,
and all were visited two or three times between June and August. The
average plankton counts per lake represent an arithmetic mean for all
visits to all stations on any one lake. Plankton samples were collected
one foot off the bottom, using a 3000 cc. Kemmerer sampler. A liter bottle
was filled and centrifuged, the concentrate preserved with formalin and
transported to Vero Beach for analysis at the E.R.C. laboratory. Identifica-
tion was carried to genus in the more readily identifiable forms but for
such groups identifiable only by rare specialists, as the blue-green algae
(= Myxophyceae), most of the identification was to cells, filaments, spirals,
or colonies only. Counting was by aliquot in a Sedgwick-Rafter cell under
the compound microscope with calibrated optical micrometers.
The distribution and abundance of plankters is shown in a summary
form in Figure 1. The poorness of the plankton in the undisturbed lakes
is evident. There is a good correlation between plankton numbers and dis-
turbance of the lakes by nutrient addition, this being especially noticeable
in the critical blue-green algae.
Protozoa occurred in all lakes but the undisturbed Lake Thomas. They
were especially abundant in Lake Lulu (7,220,048/L) where the dominant
form was an actinopod, in Lake Effie (6,852,044/L) where euglenoids pre-
dominated, and in Lake "X" (1,357,024/L) where Dinobryon and other

Provost and Branch: Food of Chironomid Larvae

chrysomonads predominated. None of the protozoan forms identified be-
longed to the recognized "sewage protozoa".
ROTIFERS varied from 13/L in Lake Thomas to an enormous 76,564/L
in Lake Lulu. Since any count above 1000 per liter is considered unusual
and the highest recorded density from unpolluted waters is 5800 per liter
(Pennak, 1953), it seems that the following lakes could be considered "pol-
luted" by the rotifer criterion: May (mostly Trichocerca and Brachionus),
"Y" (mostly Brachionus, Keratella and Trichocerca), Lena (mostly unidenti-
fied), and Lulu (mostly Trichocerca).

00 s. 10.000 S. IOO.00O5. /0.000o 10O.OOO. I0.05 00.00 /oS000.0005.
0 1 2 3 40 I 3 0 8 16 1 6 06 28 0 16 24 16 0 8 16

mI I ll"X"

8 I I Tracy
I I Conine

i I Tennessee

SI Deer
60 L I Lena

S 1 dibson
SI ll811 11 Effie

1 AflMay
S ll 1 72 4 4ll10. il Lu/u

Fig. 1. Numerical occurrence of major plankton groups in
Polk County lakes, summer 1956.

CRUSTACEA were scarce in all lakes. They were mostly Eucopepoda and
Cladocera. The total absence of Ostracoda reflected the sparsity of vascu-
lar vegetation in these lakes.
MYXOPHYCEAE were scarce in undisturbed lakes and in "industrial"
lakes. The "citrus" lakes averaged 24 and 40 million per liter while the
lakes receiving effluents from either septic tanks or sewage-treatment plants
averaged from 12 to 1616 million organisms per liter. The most widespread
forms were round cells of various sizes (Microcystis type). These were
especially numerous in Lakes Lulu and Effie, the two lakes on which munici-

52 The Florida Entomologist Vol. 42, No. 2

pal sewage-treatment plants were located. Blue-green filaments (single
cells, narrow and very long) occurred in all but the undisturbed lakes; in
Lake Lena, which bloomed chronically, they averaged 1,596,624,000 per
CHLOROPHYCEAE, exclusive of Desmids, were found in relatively small
numbers in all lakes, with Scenedesmus predominating. The latter aver-
aged 13,844,000 per liter in Lake Lulu. Desmids were in very small num-
bers but in all lakes except the two undisturbed; the predominant form
was Staurastrum.
BACILLARIOPHYCEAE were well under the blue-green algae in abundance.
They reached above 72,000 per liter only in Lakes May and Lulu. Diatoms
have a pronounced annual cycle of abundance frequently peaking in the
cold season, so their position in these lakes cannot well be judged from
summer sampling only.
As in their physical features, so in zooplankton the undisturbed lakes
resembled those studied by Pierce (1947), but the disturbed lakes were
enormously richer in rotifers, although the same genera predominated.
The phytoplankton in the disturbed lakes generally exceeded densities
found by Pierce, even those in the St. John's River when in algal bloom
(average for summer-16,600,500 blue-green cells per liter). The green
algal densities were far above Pierce's findings in the Welaka area, as
were also desmids and diatoms. On the whole, the plankton densities dur-
ing the summer of 1956 in the Polk County lakes more nearly resembled
the classically high densities found during seasonal peaks in the Illinois
River at the turn of the century (Kofoid, 1910) and in Lake Mendota
(Birge and Juday, 1922) than those found in natural Florida waters by
Pierce (1947).

Each of the 13 lakes was visited three times during the summer and
systematically sampled with a 6-inch Ekman dredge. Sampling was along
various transects intersecting at the center of the lake. Bottom character-
istics and depth were recorded for each haul. All chironomid larvae were
preserved and sent to the Vero Beach laboratory for identification and
The chironomid fauna of these lakes was not very diverse. The two
species whose food habits were studied were absent from the undisturbed
lakes. G. paripes, the predominant pest species, was most abundant in
the Winter Haven "Chain-o-lakes" and in the "citrus" lakes. T. decorus
was abundant only in one of the "industrial" lakes (L. Tracy) and in one
of the "sewage plant" lakes (L. Effie). The ecological influence of lake
bottom type precluded any correlation directly with plankton density.
Of the 127 positive dredge hauls for G. paripes, 75% were on pure sand
and 18% on peaty sand. The preference for sand and avoidance of muck
definitely restricted this species in the deeper lakes to a littoral band of
sand and peat. Small areas of sand in the deeper waters also produced
this species although the surrounding muck bottoms were devoid of them.
Although T. decorus was not absent from muck, of the 38 positive dredge
hauls 92% had sand as a bottom ingredient, while peat prevailed consider-
ably more than in the G. paripes sites. These apparent preferences for
certain bottom types in both G. paripes and T. decorus may be related to

Provost and Branch: Food of Chironomid Larvae

actual preferences for tube building material. However versatile these
larvae may be in utilizing materials, it has been shown that in choice exper-
iments chironomid larvae exhibit very definite selectivity (Ohgaki, 1942).
The preference of sand by G. paripes seems to limit the percentage of lake
bottoms available to them as living substrates, in which case hydraulic
dredging, commonly practiced in these lakes, may conceivably expand suit-
able bottom areas by mixing naturally accumulated muck deposits with
sand or exposing the underlying sands.

IV. THE FOOD OF G. paripes AND T. decorus

From the summer collections, 259 G. paripes from nine lakes and 95
T. decorus from two lakes were dissected and stomach contents studied.
For winter comparisons 25 G. paripes and 13 T. decorus were examined.
Only large larvae were used. The contents of the forepart of the alimentary
tract were much better preserved than those of the hindpart. The practice
was then set of utilizing only the gut down to and including the fourth
abdominal segment. The gut was dissected out of this portion of the larva
and its contents, usually holding together well, were dispersed in a small
amount of formaldehyde. In order to particulate the material as homogen-
eously as possible, the mixture was gently macerated in a mortar. From
this point onwards the identification and counting of plankton-which con-
stituted the entire contents-were carried out with the Sedgwick-Rafter
cell technique given above for lake plankton studies. For convenience the
larvae were pooled for each lake at each visit, the variable numbers in the
pools always being correspondingly adjusted in the final "per 1/ gut" datum.
Since plankters vary so much in size, the average green algal cell being
about 100 times the average blue-green algal cell in volume and in turn
but 1/100 the average crustacean nauplii, the commonly employed numeri-
cal representation of lake plankton (Fig. 1) gives a distorted picture of
plankton as a food supply for other animals. From measurements with
calibrated ocular micrometers, the volume, in cubic microns, was estimated
for all the common plankters found. The lake plankton volumes were then
computed (Table I) for comparisons with larval stomach contents and also
computed volumetrically (Table II).
The average half-gut of G. paripes measured 741 million cubic microns
and of T. decorus, 417 million cubic microns. The food totals for summer
stomachs (Table II) represented stomach food densities of 10% and 11/2%
for the two species while the winter densities (Table III) were, respective-
ly, 1/2% and 11/2%. By comparison the lake plankton dilutions in the sum-
mer averaged .004% for the G. paripes lakes and .015% for the T. decorus
lakes. Plankton in the larval stomachs was therefore 2500 times as con-
centrated in G. paripes stomachs as in the lake waters and in T. decorus 100
times. This gives a rough estimate of the efficiency of the filter-feeding
mechanism in these chironomid larvae.
The larvae of G. paripes fed overwhelmingly (98.7%) on phytoplank-
ton, with blue-green algae (60.7%) and green algae (31.3%) accounting
for most of the dietary. The dominance between these two algal groups
was evenly divided among the nine lakes. The blue-green algal food, vol-
umetrically, was evenly divided between colonies and single cells. The
green algal food occurred mainly as single cells, with Scenedesmus easily

The Florida Entomologist

predominating. Desmids constituted 5.9% of the total food with a maxi-
mum in any one lake of 28.3%; the predominant form was Staurastrum.
Diatoms, though numerous in the stomachs, nevertheless accounted for a
mere 0.8% of the total food bulk. Protozoa represented the same percent-
age but they did reach as high as 15% in one lake. Rotifers were taken
sparingly in larvae from several lakes and Crustacea only in one lake.
The winter stomachs presented a very different picture, with Crustacea
predominating as bulk (60.0%), green algae in second place (27.8%), and
blue-green algae in a very minor role (2.4%).

decorus. IN 10' /A PER ml.

1* 2 3 4 5 6 7 Total

G. paripes lakes



.1 tr
11.2 tr
.3 tr
.2 tr
.5 tr
.1 tr
.5 tr
tr 2.9
.7 1.4
1.5 .5


T. decorus lakes
Tracy tr 108.3 .4 tr 2.2 tr 4.2 115.2
Effie 33.2 1.5 tr 139.1 .5 3.2 177.5
Average: 16.6 54.9 .2 tr 70.7 .3 3.7 146.3

Thomas tr tr tr tr .2 .3
"X" .2 1.6 tr 13.5 .2 .2 15.6

Column headings for major plankton groups: 1. Blue-green algae, 2. Green algae,
3. Desmids, 4. Diatoms, 5. Protozoa, 6. Rotifers, and 7. Crustacea.

The larvae of T. decorus in the summer fed also predominantly on phy-
toplankton (91.7%), but more on green algae (50.8%) than blue-green
(26.2%). The blue-green algae were altogether single cells; the green
algae were likewise single cells, with Scenedesmus predominating. Desmids
figured more prominently (13.1%) than in G. paripes stomachs, with Staur-
astum similarly predominating. Zooplankton, all forms, were fed upon
more than in G. paripes, Crustacea alone amounting to 5.0% of the food by
bulk. The winter stomachs, as in G. paripes, contained far less blue-green
algae, slightly more green algae and considerably more Crustacea.

Vol. 42, No. 2


G. paripes T. decorus Aver
G. T. O
Lake: Con. Tenn. Y Lena Deer Gibs. Can. May Lulu Tracy Effie paripes decorus
No. stomachs 10 50 40 4 17 11 50 60 17 25 70 259 95

Blue-green algae 1.1 26.3 137.6 5.5 1.3 99.3 55.3 6.6 10.2 tr 2.1 45.5 1.6
Green algae 12.5 15.0 .6 .9 5.2 8.8 12.7 35.9 125.0 1.5 4.1 23.5 3.1
Desmids 5.2 4.7 tr 1.6 3.4 1.3 6.5 8.4 .1 3.2 4.4 .8
Diatoms .5 .4 tr .1 .2 .1 .1 1.8 .1 .1 .3 .6 .1
Protozoa .4 .2 1.0 1.8 tr .8 .2 2.6 tr .1 .6 .1
Rotifers 1.3 .3 .1 .1 .3 .1 tr .2 .1
Crustacea .5 .5 .3 .1 .3
Phytopl. o 19.3 46.4 138.2 8.1 10.1 109.5 74.6 52.7 135.4 4.8 6.5 74.0 5.6
Zoopl. .4 1.5 1.3 .5 1.9 tr .9 .5 2.6 .6 .4 .9 .5


Blue-green algae
Green algae

19.7 47.9 139.5 8.6 12.0 109.5 75.5 53.2 138.0 5.4 6.9 74.9 6.1

ae 5.6 54.9 98.7 64.0 10.8 90.7 73.3 12.4 7.4 tr 30.4 60.7 26.2
63.5 31.3 .4 10.5 43.3 8.0 16.8 67.5 90.6 27.8 59.4 31.3 50.8
S 26.4 9.9 tr 18.6 28.3 1.2 8.6 15.8 .1 59.3 5.9 13.1 S
[ 2.5 .9 tr 1.1 1.7 .1 .1 3.4 .1 1.8 4.4 .8 1.6
2.0 .3 .7 15.0 1.1 .4 1.8 tr 1.4 .8 1.6
2.7 .2 .9 .1 .5 1.8 tr .3 1.6
5.8 9.3 4.4 .2 5.0
98.0 97.0 99.1 94.2 84.1 100.0 98.8 99.1 98.2 88.9 94.2 98.7 91.7
2.0 3.0 .9 5.8 15.9 tr 1.2 .9 1.8 11.1 5.8 1.3 8.3

The Florida Entomologist

The larvae of both G. paripes and T. decorus live in tubes on the lake
bottoms which they build of bottom materials held by salivary secretion or
silk. Within these tubes they spin nets which strain particulate matter
out of the water made to flow through the tube by undulations of the
larva's body (Leathers, 1922; Walshe, 1947, 1951; Ohgaki, 1942; Tsilova,
1955). The net and its contents are then consumed and a new net is spun.


20 '/omo





P -e d,
L O~ \A

o ,y ',,




_ -

Fig. 2. Volumetric comparisons, on percentage basis, of major plank-
ton groups, in stomachs of G. paripes and T. decorus with plankton in
lakes from which collected.

' lIL

- --I-

C-I H n





M EL- = L.-

Vol. 42, No. 2


Provost and Branch: Food of Chironomid Larvae 57

Walshe (1951) found individual filterings to last from 1 to 5 minutes, with
undulation frequencies ranging from 111 to 200 per minute. This activity
goes on night and day. Such a feeding method can be inferred to be non-
selective except for the exclusion of very fine particles which if smaller than
the mesh of the net may pass through. In T. plumosus, Walshe (1947) found
all particles greater than 17 IA in diameter and most over 12 k retained.
Tsilova (1955) reports only that particles leaving the tubes are incompar-
ably smaller than those entering. These important details have yet to be
determined for G. paripes and T. decorus.
Correlations between lake plankton and G. paripes, larval stomachs for
the summer of 1956 are given on a percentage basis, volumetrically, in
Figure 2. The preponderance of blue-green algae in most G. paripes lakes
and G. paripes stomachs is evident, but the picture is clouded by a few
reversed ratios, as in Lakes Deer and Cannon. This may be due to the
larvae filtering out mainly the larger blue-green cells and colonies. In
both lakes small (< 100 i') cells predominated in the lake plankton, con-
stituting 99.2% of blue-green algal bulk in Lake Deer and 98.2% in Lake
Cannon. The blue-green algal cell stomach content, contrariwise, was
only 6.4% small cells in Lake Deer and 41.3% in Lake Cannon. The pro-
portion of blue-green algal material existing in the lakes as free and small
cells, which this analysis determined crudely only, may then determine the
proportion of it actually retained in the larval nets, -assuming that the
very small cells pass through the nets.




0 6 \


Fig. 3. Relationship between density of G. paripes larvae and
lake plankton density for nine Polk County lakes, summer 1956.

In all lakes but two, one of G. paripes and one of T. decorus, the pro-
portion of green algae in the stomachs was much larger than the propor-

The Florida Entomologist

tion in lake plankton. This is almost certainly related to the large size of
these cells compared, for instance, to most blue-green algal cells or diatoms.
The same would apply to desmids which were similarly favored as food in
all lakes but one. Diatoms, although reported by most of the literature
on chironomid feeding (Thienemann, 1954) as the principal food, in this
study showed poorly both in lakes and stomachs.
For virtually all lakes zooplankters constituted a greater percentage
of bulk in the lake waters than in the larval stomachs. The most likely
explanation is that their motility and large size together prevent their
being drawn into the larval nets by the slight current set up by the larval
undulations. The exceptions occurring with Crustacea and Rotatoria in
T. decorus and with Crustacea in G. paripes from Lake Lena remain un-

Glyptotendipes paripes AND Tendipes decorus.

G. paripes T. decorus

FOOD GROUPS summer winter summer winter
259 25 95 13

Myxophyceae 45.52 .10 1.57 .21
Chlorophyceae 23.53 1.16 3.13 4.27
Desmidiaceae 4.38 .23 .84 .67
Bacillariaceae .57 .02 .07 .09
Protozoa X .57 .13 .04 .03
Rotatoria .19 .03 .04 .03
Crustacea .19 2.50 .25 1.00
Phytoplankton 74.00 1.51 5.61 5.24
Zooplankton .95 2.66 .33 1.06
TOTAL 74.95 4.17 5.94 6.30

Myxophyceae 60.7 2.4 26.4 3.3
Chlorophyceae 31.4 27.8 52.7 67.8
Desmidiaceae 5.9 5.5 14.1 10.6
Bacillariaceae 0 .8 .5 1.2 1.4
Protozoa .8 3.1 .7 .5
Rotatoria o .2 .7 .7 .5
Crustacea .2 60.0 4.2 15.9
Phytoplankton 98.8 36.2 94.4 83.1
Zooplankton 1.2 63.8 5.6 16.9

TOTAL 100.0 100.0 100.0 100.0

The difficulty in correlating plankton volume with chironomid larval
numbers is that seasonal cycles in both are probably never synchronized,
so that there can be no day-to-day correlation between them any more
than there can be between plankton volume and its nutrients. The com-
plexity of production, with all its lags and periodic reversals, can be under-

Vol. 42, No. 2

Provost and Branch: Food of Chironomid Larvae

stood only after several years of systematic sampling of nutrients, plank-
ton, and larvae. In the short season here studied, there seemed to be an
inverse relationship in the case of G. paripes (Fig. 3). This resembles
the finding of Bradley (1932) in one of the few studies of mosquito (An-
opheles quadrimaculatus) numbers as related to plankton abundance, where
excessively high plankton densities in low mosquito production waters are
attributed to other environmental factors than larval feeding. The two
highest plankton lakes in Fig. 3 are Lena and Lulu, both frequently in
algal bloom.

6- 4-




3 4

2- k 3-

0- I I I
0 2 3 0 I z 3

Fig. 4. Plankton density in stomachs of G. paripes as related to den-
sity in lakes: major plankton groups. Logarithms plotted for organisms
per liter in lakes and organisms per half-gut in larvae.

If resort is made to plankton numbers rather than volumes, a relation
between G. paripes larval feeding and plankton density does appear to exist
(Fig. 4). The correlations are not very good with blue-green algae nor
with diatoms, nor with total organisms which is so much affected by these

The Florida Entomologist

small forms. But the correlations are good with green algae, desmids, and
protozoa. They are even better with individual genera within these groups,
e. g. Scenedesmus, Staurastrum, and actinopods (Fig. 5). It goes without
saying that the possibility of food intake being related to amount of food,
viz. plankton, present in the lakes is urgently in need of clarification.
Should this be definitely proven, there would be at hand incontrovertible
evidence that nutrients added to lakes increase the populations of G. paripes
by way of the food-chain effect on rate of development and hence abundance.
Accelerated individual growth rates within a population of constantly
propagating animals will directly affect production by shortening or tele-
scoping the generations and thus pyramiding the total numbers. If the
growth rate of G. paripes is proportional to the rate of food intake, a rea-

Scenedesmus S/auras/rum

3 Z _

I- II I i
2 3 4 2 3


Ot'----|---7-----------I -^--- ----i---

0 3

Fig. 5. Plankton density in stomachs of G. paripes as related to den-
sity in lakes: small plankton groups. Logarithms plotted for organisms
per liter in lakes and organisms per half-gut in larvae.

Vol. 42, No. 2

Provost and Branch: Food of Chironomid Larvae

sonable assumption, then its populations will be likewise proportional.
The amount of feeding activity, i. e. frequency of spinning nets and eating
them and rate of undulation, was measured in one species of Glyptotendipes
by Burtt (1940) and two species of the same genus by Walshe (1950, 1951).
Burtt found the activity correlated with temperature and light intensity,
and Walshe found it negatively correlated with dissolved oxygen. But the
significant finding of both workers is that the activity is completely inde-
pendent of the amount of food trapped or load of the nets. It must follow
then that light, temperature, and O2 being equal the rate of food intake
must be proportional to the food content of the water, i. e. plankton density.
This conclusion from a knowledge of the feeding behavior is substantiated
by the findings of the summer 1956 stomach analyses of G. paripes and the
plankton in the Polk County lakes producing them.

The summer's survey left no doubt about the dominant role of Glypto-
tendipes paripes in the "blind mosquito" problem. Its larvae occur on
sand-peat bottoms and appear to be adversely affected by deposition of
organic matter on lake bottoms, such as was demonstrated in Lakes Effie
and Lulu. Since, however, an increase in plankton is likely to increase
the production of this chironomid, it appears that enriching the lakes,
whether through organic or inorganic nutrients, gears the lakes to G.
paripes production at pest levels. Organic accumulations on the lake bot-
tom may check this, but if.dredging operations and other disturbing prac-
tices keep sandy bottoms exposed to larval invasion, the problem may be-
come acute. This may be the explanation for the "blind mosquito" situa-
tion in the Polk County lakes, but it remains a hypothesis to be dem-
Barrett, Paul H. 1957. Potassium concentrations in fertilized trout lakes.
Limnol. and Oceanogr. 2(3): 287-294.
Birge, E. A., and Chancey Juday. 1922. The inland lakes of Wisconsin.
The plankton. Its quantity and chemical composition. Wis. Geol.
and Nat. Hist. Surv. Bull. No. 64, Sci. Ser. No. 13. ix + 222 pp.
Bradley, G. H. 1932. Some factors associated with the breeding of An-
opheles quadrimaculatus. J. Agric. Res. 44(5): 381-399.
Brannon, Melvin A. 1945. Factors affecting the growth and distribution
of Myxophyceae in Florida. Quar. J. Fla. Acad. Sci. 8(4): 296-303.
Burtt, E. T. 1940. A filter-feeding mechanism in a larva of the Chirono-
midae (Diptera: Nematocera). Proc. Roy. Ent. Soc. Lond. 15:
Edmonton, W. T., G. G. Anderson, and D. R. Peterson. 1956. Artificial
eutrophication of Lake Washington. Limnol. and Oceanog. 1(1):
Hasler, A. D. 1947. Eutrophication of lakes by domestic drainage. Ecol-
ogy. 28: 383-395.
Kofoid, C. A. 1908. The plankton of the Illinois River, 1894-1899, with
introductory notes upon the hydrography of the Illinois River and
its basin. Bull. Ill. State Lab. Nat. Hist. 8: 2-360.
Leathers, A. L. 1922. Ecological study of aquatic midges and some re-
lated insects with special reference to feeding habits. Bull. U. S.
Bur. Fish. 38: 1-61.

62 The Florida Entomologist Vol. 42, No. 2

Ohgaki, Masakiro. 1942. (Nest building habit of Chironomus larvae.)
(In Japanese). Zool. Mag. (Tokyo) 54(10): 375-386.
Pennak, Robert W. 1953. Fresh-water invertebrates of the United States.
ix + 769 pp. New York: The Ronald Press Co.
Pierce, E. Lowe. 1947. An annual cycle of the plankton and chemistry
of four aquatic habitats in northern Florida. Univ. Fla. Studies,
Biol. Sci. Ser. 4(3), 67 pp.
Sawyer, Clair W. 1947. Fertilization of lakes by agricultural and urban
drainage. J. New Engl. Water Works Assoc. 61:109-127.
Thienemann, A. 1954. Chironomus. Die Binnengewdsser, Bd. 20. xvi +
834 pp. Stuttgart.
Tsilova, A. N. 1955. (On the filtration method of feeding of flies [Dip-
tera, Tendipedidae]). (In Russian). Doklady Academii Nauk, 105
(3): 596-598.
Walshe, B. M. 1947. Feeding mechanisms of Chironomus larvae. Nature,
Lond. 160:474.
Walshe, B. M. 1950. The function of haemoglobin in Chironomus plumo-
sus under natural conditions. J. Exp. Biol. 27: 73-95.
Walshe, B. M. 1951. The feeding habits of certain chironomid larvae (sub-
family Tendipedinae). Proc. Zool. Soc. Lond. 121: 63-79.



Prior to World War II, the 16 x 16 mesh per square inch wire screening
was widely used for excluding flies and mosquitoes from homes and build-
ings. It was not entirely satisfactory, as Herms and Gray (1944) had
stated that many Aedes and some Anopheles mosquitoes would pass through
it. Earle (1932) had approved the use of 16 x 16 mesh screening for use
in malaria control in Puerto Rico. The U. S. Army (1945), however, speci-
fied 18 x 18 mesh screening.
During World War II, a wire screening with 18 vertical wires by 14
horizontal wires was produced to replace the 16 x 16 mesh as the new size
could be manufactured more rapidly. Today, this mesh is a standard size and
has replaced the 16 x 16 mesh screening. Tests comparing the 18 x 14
mesh with the 16 x 16 mesh were discussed by Bacon (1946) and reported
in detail by Block (1946). Block found that Anopheles quadrimaculatus
and Culex quinquefasciatus were unable to pass through either size mesh.
When Aedes aegypti was used fourteen per cent of the normal sized mos-
quitoes escaped through screens of both sizes although the tolerances per-
mitted the manufacturer would result in the 18 x 14 mesh screen being
slightly less effective. From 30% to 50% of undersized A. aegypti escaped
through these screens. No differences were noted whether the 18 x 14
mesh screen was mounted vertically or horizontally.
Louvered screening is produced with the purpose of excluding sunlight
as well as insects. The louver screening used in the following tests was of
copper, painted black, and had vertical wires spaced %/ inch apart and with
17 or 23 louvers to the inch. Each louver was from .048 to .050 inches
wide and .006 to .007 inches thick. The 17 mesh screening had the louvers
tilted at an angle of about 350 while the louvers of the 23 mesh were
tilted about 250. To determine the effectiveness of this type of screening,
the 17 mesh louvered screening was compared with an 18 x 14 mesh copper
screen and the 23 mesh louvered screening with a 22 x 22 mesh fiber-glass

The louvered screening was installed in a position to simulate the ob-
stacles that would be encountered by a mosquito while it is trying to pen-
etrate a louvered screen in a window. Confined mosquitoes had to pass
upward between the downward sloping louvers in order to escape. The
interior surface of the louvered screen covering the cage thus represented
the exterior surface of the screen as it is usually installed. The 18 x 14
mesh screen was tested with the 18 mesh wire vertically and the 14 mesh
wire horizontally.
Two methods were used to test these screens. In the first method,
pint mason jars were used to hold the mosquitoes. A % inch hole was
bored in the side of the jar and a circular piece of screening replaced the

1 Contribution No. 64 of the Florida State Board of Health, Entomologi-
cal Research Center, Vero Beach.

The Florida Entomologist

jar lid and was held in place by the mason jar ring. As the screening was
cut into circular pieces, the louvers were distorted along the edges where
not supported on either side by a vertical wire. Therefore a paper disc
with a 11/2 inch by 11/ inch hole was placed between the screen and jar
ring of all jars to expose only the central portion of the screen. A small
cotton pad moistened with water was placed in each jar to maintain a suit-
able level of humidity.
A sheet metal cylinder, 19 inches in diameter and 10 inches high, had
holes, each just large enough to insert a mason jar ring, cut into it mid-
way about the circumference. In the center of the cylinder was either a
25-watt frosted light bulb or a 17-inch circular cage containing a rabbit,
to serve as attractants.
Eight female mosquitoes were blown into the pint jars through the
hole bored in the side which was then closed with masking tape. The jars
were wrapped in several thicknesses of black cloth so only light that had
passed through the screen could enter the jar. The jars were placed in a
horizontal position around the outside of the cylinder by inserting the jar
ring in the hole in the cylinder and placing a support under the bottom.
Each jar then faced inward toward the attractant and with the jar ring
fitted into the hole in the cylinder.
The second method to test the screens used large cages with dimensions
2 feet on each side. The cages were constructed entirely of wall board
except for one side which was covered by the screen to be tested. All
inside joints were sealed with masking tape to make a smooth interior.
A % inch hole in the side of the cage was used for putting mosquitoes
into the cage and a large door in the rear made it possible to insure com-
plete removal of the mosquitoes at the end of a test. Each cage contained
only a cotton pad moistened with water. The cages were arranged in
pairs, face to face and about 12 inches apart. A rectangular rabbit cage,
10 inches wide, 20 inches long and 12 inches high was placed between
the cages.
One hundred female mosquitoes were placed in each cage at the start
of a test. At the completion of the test the front of the cage was covered
with a sheet of clear celluloid, sealed with masking tape, and the mos-
quitoes knocked down with carbon dioxide. They were then collected with
an aspirator, killed and counted.
The mosquitoes used in these tests were adult females of Aedes aegypti
and Aedes taeniorhynchus. The A. aegypti were of normal size and were
secured from a laboratory strain. The A. taeniorhynchus were collected in
the field as immatures and allowed to emerge in a cage. The mosquitoes
were at least 3 days old before use, although during those tests when
light was used as an attractant, the addition of new adults into the stock
cage made it possible that a small proportion of the adults could have been
less. All adults were three days of age or older whenever a rabbit was
used as the attractant.
The tests were made at a constant temperature of 250 C. and each test
lasted from twenty to twenty-four hours. The percentage of mosquitoes
which escaped was determined by the formula where X = the total
number of mosquitoes placed in a cage, A = the total number recovered

Vol. 42, No. 2

Bidlingmayer: Mosquito Penetration Tests 65


No. of Mosquitoes Per cent Escaped
Type of* No. of
Screen Tests Run A. taenio-
Tested Escaped rhynchus A. aegypti

Light as Attractant
L 17 6** 44 0 0
4 30 2 6.7
C 18 x 14 6 47 0 0
4 26 0 0
L 23 6 46 0 0
4 30 0 0
FG 22 x 22 6 44 0 0
4 29 0 0

Rabbit as Attractant
L 17 12 94 2 2.1
12 96 42 43.8
C 18 x 14 12 93 0 0
12 95 0 0
L 23 12 95 2 2.1
12 95 3 3.2
FG 22 x 22 12 95 0 0
12 96 0 0

L = Louvered; C = Copper; FG = Fiber glass.
** Upper number for A. taeniorhynchus; lower for A. aegypti.


No. of Mosquitoes Per cent Escaped
Type of No. of
Screen Tests Run A. taenio-
Tested Escaped rhynchus A. aegypti

L 17 5 481 204 42.4
9 893 111 12.4
C 18 x 14 5 440 114 25.9
9 895 13 1.5
L 23 5 398 10 2.5
9 892 4 .4
FG 22 x 22 5 355 2 .6
9 899 1 .1

The Florida Entomologist

from the cage and B = the number of mosquitoes dead at the termination
of the test.

The results of the two tests with mosquitoes confined to pint jars and
large cages are given in Tables 1 and 2, respectively. In Table 1 the re-
sults of using light and a rabbit as attractants are shown separately as
it was noted that about six times as many A. aegypti would escape when
the rabbit was used instead of the light. With the rabbit used as the
attractant, 43.8% of the A. aegypti escaped through the 17 mesh louvered
screening while none penetrated the 18 x 14 mesh copper screen. The
differences between these screens are significant, with a P value of less
than .01. There is no statistical significance to the differences found be-
tween the 23 mesh louvered screen and the 22 x 22 fiber-glass screen.
Table 2 presents the results from tests using the large cages. Again
the loss of A. aegypti through the 17 mesh louvered screen was signifi-
cantly different (P = < .01) from the escape through the 18 x 14 mesh
copper screen. Large losses of A. taeniorhynchus through both coarser
screens are apparent. These adults were noticeably smaller than those
used in the jar tests, although both groups were collected in the field as
mature larvae or pupae. The conditions in the breeding area did not
appear to be unfavorable at the time of collection, so the cause of the
smaller size is not known. However, adults of A. taeniorhynchus smaller
than those used in these tests have been frequently observed to occur
naturally so that the use of these mosquitoes is not considered prejudicial to
the results. The intraspecific variation in size of mosquitoes is just as
important in screening performance as size differences between species.
The few escapes (Table 2) reported for the 22 x 22 fiber-glass screen are
probably due to errors made when counting mosquitoes as occasionally more
than 100 would be removed upon completion of a test.
Within the louver type of screening, the 17 mesh permitted far more
mosquitoes to escape than the 23 mesh. It is also to be noted that the 23
mesh louvered screen was superior to the copper 18 x 14 mesh screen in
retaining the smaller-sized A. taeniorhynchus (P = .01).
Aside from the retention and escape features of louver screening, it
showed itself in this testing to be rather fragile in the sense that minor
pressures distort and spread the louvers, resulting in larger openings at
those points which could in practical use diminish or nullify their mosquito
exclusion value. Such injuries to the louver screening were not present
in the testing above reported.

These experiments demonstrate that the 17 mesh louver screening is
not adequate for exclusion of the mosquitoes common in Florida. The
23 mesh louver screening may be satisfactory as long as it remains un-
damaged, i. e. never pushed against or crushed in any manner.


Bacon, R. W. 1946. Effectiveness of insect wire screening. Mosq. News,
6(2): 85-88.

Vol. 42, No. 2

Bidlingmayer: Mosquito Penetration Tests

Block, S. S. 1946. Insect tests of wire screening effectiveness. Amer. J.
Pub. Health, 36(11): 1279-1286.
Earle, W. C. 1932. Some observations of anti-mosquito screening and
screening materials. Puerto Rico J. Pub. Health & Trop. Med. 8:
Herms, W. B., and H. F. Gray. 1944. Mosquito Control. The Common-
wealth Fund, New York, p. 281.
War Department Technical Manual TM 5-632. 1945. Insect and rodent
control, p. 26.

One of our Florida entomologists, Lewis Maxwell, has just published a
handbook illustrates each species discussed with photographs taken by Mr.
Maxwell. Copies can be purchased for $1.00 from the author or from the
Great Outdoors Association, 4747 28th Street, St. Petersburg, Florida.

Dr. D. O. Wolfenbarger requests that all members of the Florida En-
tomological Society who expect to attend the International Congress of
Entomology in Vienna in 1960 get together to make plans for the meeting.
If you are interested in coordinating efforts with Dr. Wolfenbarger, he can
be reached at The Subtropical Experiment Station, Route 2, Box 508, Home-
stead, Florida.

Some interest has been shown in the names of the Honorary Members
of the Florida Entomological Society. The following list is current:
A. C. Brown
K. G. Bragdon
W. V. King
G. B. Merrill
W. W. Others.

A Cyanamid Report:

What's new with Malathion?

New intervals for Malathion- Malathion continues to be the ideal
material for late season insect control. Reduced intervals between last
application and harvest were received on these crops in 1958:
Tomatoes from 3 days to 1 day with malathion 57% Emulsifi-
able Liquid, malathion 25% Wettable Powder and
malathion 4% to 5% dusts.
Pears from 3 days to 1 day with malathion 57% Emulsifi-
able Liquid.
Squash from 3 days to 1 day with malathion 57% Emulsi-
Melons fiable Liquid, malathion 25% Wettable Powder and
4% to 5% dusts.
Brambleberry Family from 7 days to 1 day with malathion 57%
Emulsifiable Liquid, malathion 25% Wettable Pow-
der and 4% to 5% dusts.
Extended interval: The label for leaf lettuce has been extended from
10 days to 14 days. The label for head lettuce remains the same: 7 days.
New crop uses for Malathion Label acceptance of malathion for
insect control on figs and okra extends its already long crop use list to 95.
Okra For the control of aphids. Use recommended rates of
malathion Emulsifiable Liquid, Wettable Powder or dusts
up to time pods start to form.
Figs For control of dried fruit beetles and vinegar flies. Use
Emulsifiable Liquid or dusts at recommended rates. Apply
when necessary up to 3 days from harvest.
New animal claims In addition to label acceptance for direct appli-
cation on cattle, hogs, poultry, cats and dogs, malathion has received
these labels for direct application on sheep, goats and swine:
For the control of lice, ticks and keds on sheep and goats. Apply 16 lbs.
of malathion 25% Wettable Powder per 100 gallons of water. Spray
animals thoroughly. Repeat application after 2 or 3 weeks if needed.
Do not apply to milk goats. Do not treat animals under one month of
age. When applying sprays, avoid contamination of feed, food contain-
ers and watering troughs.
For the control of lice on swine, use malathion 4% or 5% dust making
a thorough application to the animals. In addition, pens should also be
thoroughly dusted. Repeat application in 10 days, and thereafter as
needed. Avoid contamination of feed, food containers and watering

Developer and producers of
malathion and parathion. crMaXa

American Cyanamid Company, A
Agricultural Division, Dept. HE, M L H


Entomology Research Division, Agr. Res. Serv., U. S. D. A.1

Resistance to DDT in house flies (Musca domestic L.) is now world-
wide. Organophosphorus insecticides have been suitable replacements
under most conditions, but resistance to many of these insecticides is also
developing (Keiding 1956, Lindquist 1957, LaBrecque et al. 1957, 1958, and
Kilpatrick et al. 1958).
Studies were initiated at the Orlando, Florida, laboratory in 1956 to
determine the effect of selection with an organophosphorus insecticide and
a chlorinated hydrocarbon when used individually, alternately, and in com-
bination, on the rate of development of resistance.
Four experimental colonies of house flies were started from the regular
(susceptible) colony by subjecting the adults of each generation to contact
sprays in a wind tunnel by the technique of LaBrecque et al. (1957).
Colony M was treated with malathion, colony D with DDT, colony DM
with a combination of malathion and DDT, and colony DM-A with DDT or
malathion alternately in successive generations. Selection was accom-
plished by exposing 100 to 200 4- to 5-day-old flies of undetermined sex
to 0.25 ml. of an odorless kerosene solution of the insecticide. After treat-
ment the flies were held for 24 hours and the mortality was recorded. The
survivors were then released in a rearing cage where oviposition medium
was available. Twenty-four hours later the eggs were collected and
placed in larval medium for rearing of the subsequent generation.
The spray used in selecting the first 12 generations of each colony con-
tained 1% of one or both insecticides, which killed about 90% of the flies.
In later generations the concentration of either toxicant was raised only
when all those colonies subjected to that toxicant could tolerate the in-
creased concentration. The concentration of DDT was increased to 5%
in the 13th generation, to 10% in the 17th, and to 20% in the 29th gen-
eration, in selecting the D, DM, and DM-A colonies. The concentration
of malathion was increased to 2% in the 29th generation in the M, DM,
and DM-A colonies.
As resistance developed its progress was followed by conducting wind-
tunnel tests with DDT and malathion against 4- to 5-day-old female flies
from the 11th, 15th, 20th, 25th, 30th, 31st, and 32nd generations. The
concentration of insecticide was varied with the resistance encountered.
After treatment the flies were transferred to screen holding cages and
supplied with 10% sugar solution on absorbent cotton pads. Mortality was
recorded after 24 hours. Duplicate tests with 20 female flies were run at
each concentration of insecticide. An LC-50 was computed from the con-
centration-mortality data, and the degree of resistance determined from
the ratio of this LC-50 to that of flies from the regular colony. The results
of these tests are presented in table 1.
After 30 to 32 generations resistance to DDT was lower in the DM-A
colony than in the D or DM colonies, but had nevertheless reached a high

1 C. R. Crittenden and P. H. Adcock assisted in these studies.




D Colony

Generation LC-50 Ratio

M Colony



DM Colo


ny DM-A Colony Regular

Ratio LC-50 Ratio LC-50

9.6 10.3
12.5 19.0
2.4 41.2
>15.4 >40.0
28.9 >40.0
12.2 28.0
12.3 35.0






lot a
lot b






lot a
lot b


Labrecque: Resistance to DDT and Malathion

level, and even the M colony had developed 10- to 30-fold resistance to
DDT. Resistance to malathion was much lower than to DDT, and was
variable between generations, but the M and DM colonies consistently
showed more than 2-fold resistance.
Since resistance to DDT was present in the M colony although the
selection was made with malathion, tests were conducted to determine
the extent of DDT detoxification to DDE. Adult flies were exposed to
residues of 3.5 mg. of p,p'-DDT per square foot on glass surfaces for 5
hours. The flies were then analyzed for internal DDT and DDE. The
analyses showed an average of 26.2 Ag. of DDT and 89.5 gg. of DDE per 100
flies, indicating a high rate of detoxification of DDT to DDE in this strain
of flies.
Keiding, J. 1956. Resistance to organic phosphorus insecticides of the
housefly. Science 123: 1173-74.
Kilpatrick, J. W., and H. F. Schoof. 1958. A field strain of malathion-
resistant house flies. Jour. Econ. Ent. 51: 18-9.
LaBrecque, G. C., and H. G. Wilson. 1957. House fly resistance to organo-
phosphorus compounds in Florida. Agr. Chem. 12: 46-7, 147, 149.
LaBrecque, G. C., H. G. Wilson, and J. B. Gahan. 1958. Resistance of
house flies in Florida to organophosphorus insecticides. Jour. Econ.
Ent. 51: 616-7.
Lindquist, A. W. 1957. Effectiveness of organophosphorus insecticides
against houseflies and mosquitoes. Bul. World Health Organ. 16:

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q: -




Museum of Comparative Zoology, Harvard University

The heterogeneous assemblage called Macromischa Roger includes more
than 80 named forms as it now stands. The genus is unsatisfactorily de-
fined, merging into Leptothorax Mayr, and it probably represents a grand
radiation of a Leptothorax stock in the Caribbean area, particularly in
Cuba. It is also clear that much synonymy exists at species level in the
group. Probably most of the synonymy involves forms that are geographi-
cal variants of single species. Another class of synonyms includes those
described chiefly during the 1930's, when W. M. Wheeler, C. Aguayo and F.
Santschi published a large number of forms within a brief period, resulting
in some double description. I have been able to compare types of most
of the forms discussed below in the Museum of Comparative Zoology (M.
C. Z.). Only some of the most obvious and relatively uncomplicated synony-
my is dealt with here.

Macromischa wheeler Mann

Macromischa wheeleri Mann, 1920, Bull. Amer. Mus. Nat. Hist., 42: 422, fig.
6, worker, female. Type loc.: Mina Carlota, Trinidad Mts., Cuba. Syn-
types in U. S. National Museum.
Macromischa wheeleri subsp. petri Aguayo, 1931, Psyche, 38: 181, worker.
Type loc.: La Vigia, Maya Jigua, Las Villas Prov., Cuba. Syntypes
Of five nest series taken in the Caibarien-Maya Jigua area of north-
eastern Las Villas, evidently seen by Aguayo at the time of his description,
three contain workers both with and without the brief propodeal teeth sup-
posedly diagnostic of petri, and all intergrades occur. Even in several
topotypical collections of wheeleri (leg. W. S. Creighton, G. Salt, E. 0.
Wilson) the propodeal angles are often distinctly developed in certain work-
ers in nests that also contain workers with perfectly rounded propodeum.
The two populations therefore differ only in the breadth of the range of
variation in propodeal armament.

Macromischa darlingtoni Wheeler

Macromischa darlingtoni Wheeler, 1937, Bull. Mus. Comp. Zool., 81: 450,
worker. Type loc.: coast below Pico Turquino, Oriente, Cuba. Syntypes
in M. C. Z.
Macromischa opalina Wheeler, 1937, Bull. Mus. Comp. Zool., 81: 451, work-
er. Type loc.: same as for M. darlingtoni. Holotype in M. C. Z.
I consider that the unique holotype of M. opalina is merely a small,
lightly sculptured worker of M. darlingtoni. The size difference is not so
great as indicated by Wheeler, and his statements about the differences in
clypeal shape and scape length are contradicted by the opalina type itself.

The Florida Entomologist

Macromischa dissimilis Aguayo

Macromischa dissimilis Aguayo, 1932, Bull. Brooklyn Ent. Soc., 27: 220,
worker. Type loc.: Buenos Aires, Trinidad Mts., Cuba. Holotype in
M. C. Z.
Macromischa chloana Wheeler, 1937, Bull. Mus. Comp. Zool., 81: 454, work-
er. Type loc.: Buenos Aires, Trinidad Mts., Cuba, 2500 to 3500 feet
altitude. Syntypes in M. C. Z. NEW SYNONYMY.
Types compare well. The greenish infuscation of the head, nodes and
gaster are seen to extend to the alitrunk in a series collected by E. O.
Wilson at Naranjo, which is also in the Trinidad Mts.

Macromischa archeri (Wheeler) new status

Croesomyrmex aguayoi var. archeri Wheeler, 1931 (July), Bull. Mus. Comp.
Zool., 72: 26, worker. Type loc.: San Vicente Valley, Vifiales, Pinar
del Rio Prov., Cuba. Syntypes in M. C. Z.
Macromischa (Croesomyrmex) bierigi Santschi, 1931 (September), Rev.
Ent., Rio de Janeiro, 1: 273, fig. 7, worker. Type loc.: Vifiales, Pinar
del Rio Prov., Cuba. Types in Santschi Coll., Naturhistorisches Mu-
seum, Basel; not seen. NEW SYNONYMY.
Santschi's description and figure leave no doubt that his bierigi is the
same as the var. archeri from the same general locality. E. O. Wilson
has also collected several nest series of this form in the Vinales area and
from Las Acostas, Pinar del Rio, somewhat farther west. The var. archer
is essentially like M. aguayoi Wheeler, but has the head smooth and shining
above over the posterior half or third. In aguayoi the back of the head is
subopaquely sculptured (opaquely sculptured in subsp. natenzoni Aguayo).
M. barroi Aguayo is another member of this complex.
It is most convenient now to treat archeri, aguayoi, natenzoni and
barroi arbitrarily as species. But it seems likely, when collections from
the mountains of Pinar del Rio are more complete, that these four close
allopatric forms will prove to be only local populations of a single variable

Make plans now to attend the



in Miami on September 10 and 11.

Vol. 42, No. 2


Three of the four species here recorded from Florida (two cockroaches
and one earwig) are primarily West Indian, and the fourth, Conocephalus
cinereus (Thunberg), a small widespread katydid, is more dominant there
than in Central or South America. One of the cockroaches, Hemiblabera
tenebricosa R. & H., was taken on Key Largo, Florida, more than 60 years
ago, but a recent capture on Elliott Key is of interest in confirming its
recent occurrence in Florida. Except for C. cinereus, which has been
taken about 35 miles northwest of Lake Okeechobee, records of these four
species in the United States are limited to Dade County or the Keys. The
earwig, Pyragropsis buscki (Caudell), is represented by three specimens,
all taken within about ten miles of Miami. This species is the first mem-
ber of the family Pygidicranidae to be recorded from the United States.
Except as noted, all specimens recorded are in the U. S. National.
I am grateful to the following scientists who have assisted materially
by their generous cooperation in supplying specimens or collection data, or
by making other specimens available for comparison: R. M. Baranowski,
Subtropical Experiment Station, Homestead, Florida; H. H. Keifer, Cali-
fornia Bureau of Entomology, Sacramento, California; J. A. G. Rehn, Acad-
emy of Natural Sciences of Philadelphia; Albert Schwartz, Albright Col-
lege, Reading, Pennsylvania; H. F. Strohecker, University of Miami, Coral
Gables, Florida; Howard V. Weems, Jr., Florida State Plant Board, Gaines-
ville, Florida.
Eurycotis lixa Rehn (Orthoptera, Blattidae)
Figures 12-14
U. S. records: Key West, Fla., July 1952 (Schwartz and Porter), 1 female;
Key West, Fla., Sept. 21, 1956 (W. W. Warner), 1 female.
Other records: "Taken at New York City on banana ship from Jamaica,
Oct. 20, 1924 (F. M. Schott)", 1 male holotypee), 1 female (allotype)
(Acad. Nat. Sci. Phila.). Original material described by Rehn (Trans.
Amer. Ent. Soc. 56: 45-48, pl. 4, figs. 1-9, 1930).
This species was thought by Rehn (1. c.) to be native to Jamaica. Un-
fortunately, no confirming data are available. Concerning the Key West
specimen taken in 1952, I am indebted to one of the collectors for com-
ments about the circumstances of capture. Dr. Albert Schwartz (in litt.,
Oct. 8, 1955) stated that the specimen was collected at night in the "down-
town" section of Key West, probably along a low wall which separated
a garden from a sidewalk. Regarding the 1956 specimen, Dr. Howard V.
Weems has informed me (in litt., April 25, 1958) that three additional speci-
mens of lixa were taken by Mr. Warner.
The Key West specimens were identified by comparison with the types
of lixa and a review of described species, especially the West Indian species
treated in my 1942 key (Bull. Mus. Comp. Zool. 89: 34-37). E. lixa (fig.

SEntomology Research Division, Agricultural Research Service, U. S.
Department of Agriculture.

The Florida Entomologist

12) is approximately the same size as E. floridana (Walk.), which was
shown in habitus sketch by Hebard (Mem. Amer. Ent. Soc. 2: pl. 6, fig. 11,
1917) and in photographs by Roth and Willis (Smithsonian Misc. Coll. vol.
122, no. 12: pls. 1, 3, 5, 1954).
E. floridana, the only other species of Eurycotis established in the
United States, has very broad, subquadrate tegmina, quite unlike the lat-
eral subtriangular tegmina of lixa, which in the Key West specimens vary
as in figs. 13-14 and differ slightly from those of the allotype (Rehn, 1. c.,
pl. 4, fig. 4). Most specimens of floridana are definitely brownish, whereas
lixa is essentially black to the naked eye, though under magnification in
a strong light a brownish tinge is noticeable, this being more conspicuous
in the 1952 than in the 1956 specimen. The basal segment of the hind
tarsus of lixa is more elongate than that of floridana, and the pulvillus oc-
cupies about one-fourth the ventral length of the segment, as contrasted
with one-third to one-half the length in floridana.
Compared with E. tibialis Hebard of Hispaniola, lixa is blacker, aver-
ages larger, and the hind tibia is not broadened and pitted as in tibialis (see
Gurney, 1. c., fig. 4). The Brazilian E. manni Rehn is much like lixa, but
differs noticeably in that the latero-posterior angles of abdominal terga 5-7
are only briefly produced as acute points. E. manni was described by Rehn
(Trans. Amer. Ent. Soc. 42: 238-239, pl. 14, fig. 15, 1916), based on a single
male. I have examined a male in the U. S. National Museum collected at
Natal, Brazil, May 1925, by E. C. Green. Apparent relationship to E. nigra
Princis may also be noted. Described from Caracas, Venezuela (Ann. Istit.
Mus. Zool. Univ. Napoli 4: 4-6, fig. 2, 1952), nigra is smaller (body length
of male 20 mm., pronotum 5.5), and the lateral tegmina have the apices
reaching almost to the hind margin of the metanotum.
The two Key West females of lixa show some variation in the number
and position of the spines borne by the hind tibia, and neither agrees ex-
actly with the allotype as regards the spines on the outer lateral margin
of the hind tibia (Rehn, 1. c., pl. 4, fig. 8). Respective measurements in

i Explanation of Plate
1. Pyragropsis buscki (Caud.), male genital armature, non-KOH prepa-
ration in alcohol. Jamaica.
2. Same, partial details of distal lobe, KOH preparation on slide. Cuba,
intercepted at N. Y.
3. Same, male forceps of elongate type, dorsal view. Holotype.
4. Same, male forceps of arcuate type, ventral view including apex of
subgenital plate. Same specimen as fig. 1.
5. Same, female forceps, dorsal view, reconstructed from broken speci-
men. Palm Island, Fla.
6. Conocephalus fasciatus fasciatus (De G.), left cercus of male, dorsal
view. Alachua Co., Fla.
7. C. cinereus (Thunb.), left cercus of male. Martin Co., Fla.
8. Same, left cercus of male, laterodorsal view. Same specimen as fig. 7.
9. C. fasciatus, left cercus of male, laterodorsal view. Same specimen as
fig. 6.
10. Same, fastigium of female, dorsal view. Martin Co., Fla.
11. C. cinereus, fastigium of female, dorsal view. Martin Co., Fla.
12. Eurycotis lixa Rehn, dorsal view of female. Key West, Fla., July 1952.
13. Same, left tegmen, dorsolateral view. Key West, Fla., Sept. 21, 1956.
14. Same, left tegmen, dorsolateral view. Key West, Fla., July 1952.
(All drawings by the author)

Vol. 42, No. 2

Gurney: Records of Orthoptera and Dermaptera 77

di. lo

1 pm

T 54

7 64


9 _

The Florida Entomologist

millimeters of the 1952 and 1956 specimens are as follows: Body length,
34.0, 36.0; interocular width, 4.0, 3.7; length of pronotum, 10.5, 9.8; maxi-
mum width of pronotum, 14.6, 14.0; costal length of tegmen, 6.7, 5.7; max-
imum width of tegmen, 3.3, 3.2; length of hind tibia, 13.0, 11.7; length of
hind tarsus, 8.7, 8.0.

Hemiblabera tenebricosa Rehn and Hebard (Orthoptera, Blattidae)
U. S. Records: Elliott Key, Fla. [about 20 miles south of Miami], about
1952 (Ray Porter), 2 females (Strohecker Collection); Key Largo,
Fla., Jan. 1896 (E. A. Popenoe), 1 male, 1 female.
Other records: West Indies, including Nassau, Bahamas (Rehn and He-
bard, Bull. Amer. Mus. Nat. Hist. 54: 271-274, pl. 19, figs. 9-11, 1927).
Brief comments on tenebricosa, including the Key Largo record, ap-
peared in my 1953 paper (Gurney, Proc. U. S. Nat. Mus. 103: footnote, p.
46). This is a predominantly reddish-brown cockroach, ranging from 32
to 46 millimeters in body length, and with subquadrate tegmina covering
less than half of the abdomen. In view of the recent Elliott Key records,
it appears to be established in the Florida Keys, and perhaps on the ad-
jacent mainland.

Conocephalus cinereus (Thunberg) (Orthoptera, Tettigoniidae)
Figures 7-8, 11
U. S. records: Sebring, Fla.,'Nov. 25, 1954 (H. V. Weems, Jr.), 1 male;
Martin Co., Fla., Nov. 5, 1954 (H. V. Weems, Jr.), 8 males, 2 females;
Dade Co., Fla., Oct. 22, 1954 (H. V. Weems, Jr.), 2 males, 4 females;
Homestead, Fla., Dec. 2, 1946 (D. O- Wolfenbarger), 1 male. (Fore-
going specimens Fla. Plant Board and USNM). 8 miles east of Home-
stead, Fla., Jan. 17, 1957 (R. M. Baranowski), 2 males (Baranowski
and Strohecker collections).
Other records: This is a well known species of the Neotropical region,
occurring from the Bahamas and northern Mexico to British Guiana
and Peru. Tampico and Mazatlan are northern known limits in Mex-
ico. It is a dominant species of the genus in the Bahamas, Greater
Antilles, and northernmost Lesser Antilles (Rehn and Hebard, Trans.
Amer. Ent. Soc. 41: 243-248, 1915); Hebard, Ibid. 58: 335, 1932). It
was not listed by Piran in his catalogue of Argentine Tettigoniidae
(Rev. Soc. Ent. Arg. 11: 119-168, 240-287, 1941 and 1942).
Conocephalus cinereus was originally described from Jamaica, and has
been discussed fully by Rehn and Hebard (1. c.). It has been reported as in-
jurious to tobacco seedlings at San Lorenzo, Puerto Rico, by Wolcott (Jour.
Agric., Univ. P. R. 32: 54, 1950). Dr. R. M. Baranowski (in litt., May 19, 1958)
has reported that the specimens he collected were actively feeding on the
banded cucumber beetle, Diabrotica balteata Lec. Among the few studies
of food habits of the genus Conocephalus are those of the late F. B. Isely
dealing with C. fasciatus (De G.) (Isely, Ann. Ent. Soc. Amer. 37: 62,
1944; Isely and Alexander, Science 109: 115-116, 1949), on the basis of
which he concluded that Conocephalus is mainly carnivorous and seed-eat-
ing. It appears that careful observations are required to determine the
exact food preferences of these small orthopterons.
C. cinereus is a small, slender katydid, or "meadow grasshopper," about
16 to 27 millimeters in length (including apices of folded tegmina). It is

Vol. 42, No. 2

Gurney: Records of Orthoptera and Dermaptera

most likely to be confused with C. fasciatus, a species very widespread in
the United States. The best feature enabling the separation of the two
species is the cerci of adult males (figs. 6-9). The cercus of cinereus has
on the dorsal surface a distinct flattened apical portion, but that of fasciatus
is tapered near the apex. The cercus of cinereus usually is the same color
as the apical portion of the abdomen, normally yellowish or light brown,
while that of fasciatus usually is green, in contrast to the abdomen. In
both sexes the lateral lobe of the pronotum is a helpful separating feature:
In cinereus the humeral sinus is less evenly and broadly rounded, and the
ventral margin is about right-angled, in contrast to the more evenly and
broadly rounded humeral sinus and very broadly rounded ventral margin
in fasciatus (see Rehn and Hebard, Trans. Amer. Ent. Soc. 41: pl. 17,
fig. 2, pl. 22, fig. 12, 1915). When seen in dorsal view, the apical portion
of the fastigium of cinereus usually shows lateral expansion, rather than
approximately equal width as in fasciatus (figs. 10-11).
Other species of Conocephalus recorded from Florida are aigialus R. &
H., brevipennis (Scudd.), fasciatus fasciatus (De G.), gracillimus (Morse),
nigropleuroides (Fox), and spartinae (Fox). Material of fasciatus from
Martin Co., Fla., with label data identical to that of cinereus, has been ex-
amined, suggesting that both species may occur together in some areas.
The most distant Floridian localities occupied by cinereus are some 150
miles apart, and the earliest record is 1946, so the species appears to be
well established. It is one of the very few katydids occurring in both the
United States and South America. Isely (Ecol. Monogr. 2: 470, 1941)
stated that Neoconocepharus triops (L.) is unique in such a distribution,
and in a hasty check I had found no others until, now, C. cinereus.

Pyragropsis buscki (Caudell) (Dermaptera, Pygidicranidae)
Figures 1-5

U. S. records: Little River, Fla. [adjacent to Miami] intercepted in plant
quarantine inspection of box of palm seed, at Redondo Beach, Los
Angeles Co., Calif., March 9, 1947 (through H. H. Keifer), 1 male;
Palm Island, Miami Beach, Fla., in house, July 24, 1951 (M. B. Byrne),
1 female; Key Biscayne, Fla., on Cocoa nucifera, June 5, 1958 (C. F.
Dowling, Jr.), 1 female (Fla. Plant Bd.).
Other records: Baracoa, Cuba, Oct. 14, 1901 (August Busck), 1 male (holo-
type), 1 nearly mature female; Cuba, intercepted in plant quarantine
inspection at New York City, May 6, 1937, 1 male; Jamaica, in rotten
palm, March 12, 1907 (J. R. Johnston), 3 males; Dominican Republic,
intercepted in plant quarantine inspection at New York City, July
1934, 1 female.
This species originally was described in the genus Pyragra by Caudell
(Jour. N. Y. Ent. Soc. 15: 166-167, 1907). It was listed in the genus Pro-
pyragra by Burr (Trans. Ent. Soc. London, p. 167, 1910; Gen. Insect. 122:
22, 1911). Rehn and Hebard (Bull. Amer. Mus. Nat. Hist. 37: 635-636,
1917) transferred it to the genus Pyragropsis and recorded a male from
Santiago de Cuba, Cuba. Gowdey (Cat. insect. Jamaicensis, Dept. Agric.
Jam. Ent. Bull. 4: 9, 1926) recorded it from Jamaica as Pyragropsis buscki.
No records additional to those cited have come to my attention.
P. buscki varies in body length from 14 to 19 millimeters, and is fully
winged. The abdomen is dark reddish-brown; the pronotum and tegmina

The Florida Entomologist

light brown, the pronotum pale in the central area and along the lateral
margins, each tegmen with small pale area near base; exposed portion of
folded wings pale adjacent to tegmen; both tegmina and tip of folded wing
bear numerous short stiff setae. Male forceps of two types (figs. 3-4),
either evenly arcuate or more elongate; posterior margin of subgenital
plate emarginate. Female forceps elongate with numerous denticulations
(fig. 5); posterior margin of subgenital plate narrowly projecting mesally;
terga 5-7 each with a very pronounced longitudinal ridge along lateral mar-
gin in male, ridge absent in female. This species differs from all other
United States earwigs in the possession of a well developed padlike arolium
between the tarsal claws, as illustrated for the Costa Rican P. tristani
Borelli by Burr (Gen. Insect. 122: pl. 3, fig. 2a, 1911). The only other
United States earwigs whose males have forceps at all resembling those
of buscki are the species of Euborellia and Anisolabis, and of these E.
cincticollis (Gerst.) is the only one here with fully developed wings, though
rare winged examples of E. annulipes (Lucas) have been recorded abroad.
The pronotum, tegmina and wings of cincticollis (which is frequently but
not always winged) bear no such conspicuous setae as occur in buscki. A
list of the United States species accompanied the initial report of cincticol-
lis in this country (Gurney, Proc. Ent. Soc. Washington 52: 200-203, 1950).
P. buscki is the only species of Pygidicranidae in the United States. For
information on the relationships of the family and genus, readers may con-
sult the keys and references given by Hincks (Acta Zool. Lilloana 7: 623-
652, 1949) in his comprehensive paper on Argentine earwigs. The male
armature of buscki is distinctive, and differs from that of P. brunnea (Burr)
of Argentina (Hincks, 1. c., p. 627, fig. 1) by having curved parameres
(fig. 1, pm) instead of relatively straight ones. Presumably the sclero-
.tized structures of the distal lobes (di. lo.) (see fig. 2) also differ, but de-
tails of those structures in brunnea are not available to me. Hincks (pp.
66-69 in Taxonomist's glossary of genitalia in insects, S. L. Tuxen, Ed.,
1956) has briefly discussed the anatomy of earwig genitalia.

Make plans now to attend the



in Miami on September 10 and 11.

Vol. 42, No. 2

ARROW 1, 2

Everglades Experiment Station, University of Florida

The larvae of the northern masked chafer, Cyclocephala borealis Arrow,
occur frequently among the roots of grasses in organic soils of the Ever-
glades. They do not frequently cause noticeable damage to pastures but
often distress the sod grower when he harvests his product. The sod pieces
tend to fall apart as a result of root pruning and loosening of the soil when
lifted from the soil surface. Under drought conditions root damage has
resulted in the death of the grass.
On October 12, 1958, the author visited two pastures, one in pangola-
grass, Digitaria decumbens Stent., at Clewiston and the other in St. Augus-
tinegrass, Stenotaphrum secundatum (Walt.) Kuntze, at Belle Glade that
were heavily infested with northern masked chafer larvae that were causing
brown areas. At each site there were approximately 8 to 10 grubs per
square foot.
At the Belle Glade pasture five (17%) of thirty chafer larvae collected
appeared to be diseased. Some of the sick larvae were flaccid and more
opaquely white than healthy grubs, whereas others were darker and even
more limp denoting a more advanced stage of the disease.
Diseased grubs were sent to Dr. S. R. Dutky, Beekeeping and Insect
Pathology Section, U. S. D. A., Beltsville, Maryland. Dr- Dutky replied:
"The specimens were examined and all were found to be milky diseased.
The organism present in all specimens closely resembles the Cyclocephala
strain of Bacillus popilliae."
Dutky (1940) described and named the organism, Bacillus popilliae
Dutky, that is the causitive agent of type A milky disease of the Japanese
beetle, Popillia japonica New. Dutky (1941) stated that Cyclocephala
borealis Arrow larvae were susceptible to type A milky disease infection
by injection and puncture inoculations and that a few instances of natural
infection with type A milky disease had been found. White (1947) found
northern masked chafer larvae in the field that were naturally infected
with the milky disease. In most instances the causative agent was an or-
ganism similar to that causing type A milky disease. The milky disease
was designated originally as atypical type A but later called type A
(Cyclocephala strain). White reported an instance of northern masked
chafer grub control with atypical type A milky disease at a site where the
Japanese beetle grubs were infected with regular type A milky disease.
He cited this as an indication that both organisms were present and work-
ing independently. A full description of the disease, the causative agent,
and a review of the literature are given by Steinhaus (1949).

SFlorida Agricultural Experiment Station Journal Series, No. 783.
2 The author wishes to thank Mr. C. E. Seiler for help in making obser-
vations and Mr. Edward King, Jr. for preparing the graph.

82 The Florida Entomologist Vol. 42, No. 2

60 12

50 % Diseased Grubs 10

In \\ \
8 40 8
o \ / \
S30 6-

20\ Grub Population /sq.ft. 4

10 -.. 2

0 0
Oct. Oct. Oct. Oct. Nov.
12 18 -23 31 6
Observation Dates
Fig. 1. Northern masked chafer grub population and incidence of milky-
diseased individuals on several dates in a St. Augustine grass pasture.

The Belle Glade pasture was visited at 6 to 8 day intervals and exam-
inations were made to obtain an estimate of the average number of grubs
per square foot and the percentage of grubs that were diseased. Obser-
vations were hampered by difficulty in finding grubs that had decomposed
after death. The area of soil examined gradually became larger as it be-
came more difficult to find grubs because of the decreasing population.
The number of grubs examined on each date was as follows: 12 October-
30; 18 October-50; 23 October-52; 31 October-53; 6 November-21.
The area of pasture soil examined on October 18 was not recorded so no
estimate of the grub population per square foot is recorded for this date.
In less than one month the number of grubs per square foot fell from 9
to 0.5 at the Belle Glade pasture (Figure 1). The percentage of diseased
grubs increased from 17% on October 18 to 52% on October 23. It fell to
34% on October 31 but rose to 52% on November 6.
The pasture at Clewiston was not examined periodically, but Mr. W. G.
Genung visited this location in late October and observed that there was a
high incidence of diseased individuals and the grub population was greatly
It seems that the dry summer exaggerated the damage done by the
grub and was unfavorable to the dissemination of the disease organism and
inoculation of grubs. The wet soil caused by heavy rains during October
and November probably accelerated dissemination and inoculation.

Harris: Occurrence of a Milky Disease Among Larvae 83

Dutky, S. R. 1940. Two new spore forming bacteria causing milky dis-
ease of Japanese.beetle larvae. Jour. Agr. Res. 61(1): 57-68.
Dutky, S. R. 1941. Susceptibility of certain scarabaeid larvae to infec-
tion by type A milky disease. Jour. Econ. Ent. 34(2): 215-216.
Steinhaus, Edward A. 1949. Principles of insect pathology. McGraw-
Hill Book Company, Inc., New York. Pp. 258-276.
White, Ralph T. 1947. Milky disease infecting Cyclocephala larvae in the
field. Jour. Econ. Ent. 40(6): 912-914.

Specialist! :#'

This handsome fellow specializes 1
in "inside jobs." He's the corn
borer. He may not be the ugliest
insect known to Agriculture, but
the damage he inflicts ranks him
right up there with the worst. i :
One fact remains very clear. The
corn borer and his flying, crawling,
burrowing and hopping "cousins" still get too large a share of
Agricultural production.
Only through continuing research and experimentation can we
hope to win the vigorous-battle with the insect world. Shell
Chemical Corporation, with the valuable co-operation of inde-
pendent entomologists, U.S.D.A. staff researchers, extension work-
ers and growers, strives to develop better and more successful
pesticides to reduce crop losses.
Modern Shell pesticides, now in use as a result of this close
co-operation, include aldrin, dieldrin, endrin, Methyl Parathion
and Phosdrin insecticides; D-D and Nemagon Soil Fumigants
and Allyl Alcohol weed seed killer.
Newer pesticides, now in the laboratory stages at Shell Chemi-
cal's experimental research center at Modesto, California, promise
an even more effective defense against insects.

Shell Chemical Corporation looks to a better tomor-
row for Agriculture through chemical research today.
For technical information on Shell products, write to:





In 1956, Fisher (1957) found that zineb could be used to control citrus
fruit russet. For many years sulfur had been the only known material
which would satisfactorily kill rust mites, and thus prevent rust mite in-
jury on fruit russeting. Fisher reported outstanding success with zineb.
This stimulated considerable interest in the material, and a more detailed
report was made by Johnson, et al. (1957) at the 1957 meetings of the
Florida State Horticultural Society. They concluded that zineb killed rust
mites and that it was very effective when applied during the post bloom,
summer and fall spray periods. They reported good results with dosage
as low as 1/ pound per 100 gallons of spray material.
Work with zineb was started by the Eloise Groves Association in Jan-
uary 1957 in four 40-acre blocks of 12-year-old Valencia oranges. Four
rows were set aside in the center of each block. Two of these in each
block were sprayed with zineb by a Speed Sprayer driven at 2% miles per
hour and applying approximately 5 pounds of zineb per acre. The other
two rows were sprayed with a Speed Sprayer driven at 11% miles per hour.
In both blocks a double-headed machine was used. A similar application
was repeated at the post bloom period. In the summer, the two rows where
the Speed Sprayer had been driven at 2/2 miles per hour were sprayed
with a combination of oil-parathion and approximately 5 pounds of zineb
per acre. The other two rows in each block were sprayed with a similar
combination but at the rate of only 21/2 pounds of zineb per acre. In both
instances, a Model-36 Sprayer was used and the material was applied at 1
mile per hour with a single head. The remaining portion of all four blocks
was sprayed with conventional wettable sulfur programs for rust mite con-
trol. In only one of the four zineb-sprayed blocks were additional sulfur
sprays required for rust mite control. In this one block, one extra spray
was sufficient. In the case of the standard wettable sulfur sprays, at least
three additional sprays or dusts were required in each of the four blocks
in order to maintain rust mite control throughout the fall. No differences
were noted between rates of speed of application or between the amounts
of zineb used in the summer application.

During the summer scalicide period in 1957, zineb was applied in com-
bination with oil or oil-parathion on more than 50% of the total acreage in
Eloise Groves Association. In almost all cases zineb was used at 5 pounds
per 500-gallon tank and applied at a rate of 10 pounds per acre on oranges,
15 pounds per acre on grapefruit and approximately 5 pounds per acre on
trees which averaged about 10 to 12 years of age. In some blocks, this
dosage was cut in half so the comparison could be made between the two
rates of zineb.

SA report presented at the 41st annual meeting of the Florida Entomo-
logical Society, August, 1958.
2 Production Manager, Eloise Groves Association, Winter Haven, Florida.

The Florida Entomologist

Zineb was found to be very effective in controlling rust mite infesta-
Table I shows the number of spray or dust applications which were re-
quired, following the summer scalicide spray, in order to maintain rust
mite control throughout the late summer, fall, and early winter months.
The only differences of any consequence will be noted between the presence
or absence of zineb in the summer scalicide spray. Wherever zineb was
used, regardless of the dosage, less applications were required.


Lbs. Zineb per 500-Gal. Tank

Scalicide Grapefruit Oranges

0 21 5 Avg. 0 2% 5 Avg.

Oil 1.6 0 0.5 1.1 1.4 0.6 0.4 0.8
Parathion 1.7 0.2 1.0 2.4 0.8 0.8 1.3

Table II shows the actual number of days that elapsed between the time
that the summer scalicide spray was applied and the time that an additional
application was required for rust mite control. Some of the figures show
a plus mark, which indicates that the period was longer than that listed.
SThus, in many instances, no additional sprays or dusts were required until
the post bloom application in 1958, but the tabulations were terminated
during December, 1957. In this table, it becomes obvious that zineb was
markedly superior to straight oil or oil-parathion, and that the 2/2 pounds
per tank were not quite as effective as the 5 pounds. However, the 2
pounds were sufficiently satisfactory that there appears to be little justifi-
cation for using the higher dosage. This is in line with results presented
by Johnson (1957).


Lbs. Zineb per 500-Gal. Tank


0 21/2 5

51 81 104+

23 114+

Avg. 37


0 22 5

54 114


24 71 116+

39 83 114+



Vol. 42, No. 2

- 109+

Griffiths: Results from Use of Zineb in Citrus Groves 87

It should be noted here that, in a few places, russeting did occur fol-
lowing zineb application. This occurred where heavy infestations were not
controlled with a zineb spray.
In a commercial operation, if rust mite control can be maintained from
June or July for a period of approximately 90 days, it is possible to use
sulfur dusts as an effective and economical method of rust mite control.
Thus, it would be cheaper to apply an additional one or two dusts at this
time than to use the increased amount of zineb during the summer scali-
cide spray in order to obtain somewhat longer control.
In three cases where the cost of the spray program was calculated in
paired blocks, it was found that the zineb program resulted in savings of
15 cents, $4.60 and $1.90 per acre, when labor, equipment and materials
were all included at standard cost figures. However, the cost picture does
not tell the entire story, since the use of zineb resulted in less necessity
for checking the grove for rust mites, and in a much more flexible work
Due to the disastrous freezes during the winter of 1957-58, no dormant
sprays were made in Eloise Groves Association. Rust mites were at a
generally low level throughout the winter, and post bloom sprays were
applied during April, 1958. During this operation comparisons were made
between sprays containing only sulfur; copper and sulfur; zineb and cop-
per; and zineb alone. Some sprays contained zinc, manganese, or arsenic,
but these materials were ignored so far as the results reported here are
concerned. All sprays were concentrated and were applied with a Speed-
Sprayer, using a double head and driven at 21/ miles per hour. Mature
groves received zineb at approximately 5 pounds per acre. Groves in the
10 to 14-year-old category received only 3 pounds per acre. The results
of these sprays are shown in Tables III and IV.
Table III shows the results where copper was included in the spray,
and Table IV where no copper was present. The groves are divided into
four categories depending on age and variety. The number of groves
sprayed with each combination is shown; the average percentage number
of fruit infested with rust mites is shown for the approximate dates of June
1st and July 1st. Some of the figures for July 1st are shown with a plus
mark, which indicates that the populations would have been higher but,
of necessity, were sprayed prior to the July 1st count. In the fourth column
under each category is shown the percentage of groves in which rust mites
were sufficiently high that treatment was required by approximately
June 15th.
Zineb was materially superior to sulfur whether or not copper was
included, but the inclusion of copper in the spray resulted in a reduced rust
mite control with both materials. In spite of the reduction where copper
was used with zineb, this was still a superior application to wettable sulfur
alone. In no instance was it necessary to re-treat any of the groves sprayed
with either zineb or zineb-copper prior to the summer scalicide.

As this report is being presented at the Annual Meeting of the Florida
Entomological Society, it is impossible to finally evaluate the summer scali-




No. Rust Mites
Groves June 1 July 1

Old Grapefruit
Old Oranges
Old Tangerines
Oranges (8-14 yrs.)

Retreated No.
By June 15 Groves

Rust Mites
June 1 July 1


By June 15

0 5




No. Rust Mites
Groves June 1 July 1

Old Grapefruit
Old Oranges
Old Tangerines
Oranges (8-14 yrs.)

By June 15





% Groves
Rust Mites Retreated
June 1 July 1 By June 15

0 0
0 P



Griffiths: Results from Use of Zineb in Citrus Groves 89

cide sprays. However, certain trends have become obvious and the results
are worth noting here.
Zineb was applied in most instances in concentrated oil-parathion com-
binations with Speed Sprayers driven at 1 mile per hour. Model-40 Spray-
ers used a double head, and Model-36 Sprayers used a single head. On
groves of approximately 10 to 14 years of age, about 3 pounds of zineb
were applied per acre. On old oranges approximately 5 pounds were ap-
plied per acre, and on old grapefruit about 7 pounds were applied. At
approximately 135 locations, rust mites were at a very low level when the
summer scalicide was applied. As of the middle of August rust mites have
not appeared in sufficient numbers to be cause for alarm in any of these
blocks. In 32 locations, 20 grapefruit and 12 orange or tangerine, in which
more than 40% of the fruit was infested at the time of the summer scali-
cide spray, failures were recorded in 75% of the grapefruit and approx-
imately 20% of the orange and tangerine blocks. The criterion of failure
was that 25% or more of the fruit was infested. In general, the infested
fruit was found inside the tree, usually as clustered grapefruit. Leaves
were generally completely uninfested, and outside fruit had a very low
rate of infestation.
These results suggest that when high infestations are present at the
time that the summer scalicide is applied, it may be well to increase the
dosage of zineb. Whether or not this would result in fewer failures remains
to be determined, but it is worth considering during the 1959 spray season.


The results presented here, as well as those by many other commercial
operators in Florida, all point up the fact that zineb gives excellent rust
mite control. They show that zineb is effective both at post bloom time
and during the summer scalicide period, that it may be applied at as little
as 5 pounds per acre on old groves, and that coverage, at least during the
post bloom period, is not as critical as may have previously been believed.
The data presented here indicate that none of the failures following
the 1958 summer scalicide were groves in which straight zineb was applied
at post bloom time. However, three failures followed a post bloom copper/
zineb. All other failures followed the use of straight sulfur or copper-
sulfur at post bloom. This is certainly suggestive that the use of zineb at
post bloom time would result in better rust mite control, not only during
the late spring but also following the summer scalicide period. If it can
be successfully used when applied at 21/2 miles per hour and relatively low
dosage, the elimination of failures following the summer scalicide will
justify any additional cost of material at post bloom time. Additional in-
formation is necessary to establish this as fact, but the suggestion that
zineb be used at post bloom time is made for the 1959 season.
No results observed by the author give any indication of deleterious
results from the use of zineb. This does not mean that such will not be
the case in the future, as it may take several years for adverse results to
become evident. Since zineb is a fungicide, it is to be expected that there
may well be an increase of some insect or mite populations, perhaps even
of insects or mites that have normally been considered to be of no economic
importance in the past. It is possible that the elimination of sulfur from

The Florida Entomologist

a spray program may also have deleterious effects, but no such results
have yet become evident.
During both the 1957 and 1958 seasons, various combinations of zineb
and wettable sulfur were tried. These varied from dosages of 1 pound of
zineb with 50 pounds of wettable sulfur to 3 pounds of zineb with 25 pounds
of wettable sulfur per 500-gallon tank, with approximately 1 tank of
material being applied per acre of old grove. The replications of these
dosages were too small to present here as averages. However, even the
addition of 1 pound of zineb in a 500-gallon tank appears to have resulted
in materially enhanced rust mite control. There have been no instances when
these combinations as compared with wettable sulfur were not strikingly
better than the wettable sulfur applications. Comparisons are too scanty
for valid conclusions to be drawn, but they are very suggestive that such
combinations should be further studied as they may represent a very satis-
factory application for some periods of the year. If it becomes evident
that sulfur is needed for the control of some insects, it may well be that
zineb-sulfur combinations offer the correct answer. Certainly these com-
binations are well worth considering as a permanent part of a spray pro-
gram during the coming years.
At the present time it is impossible to speak with authority on the
type of over-all spray program that should be carried out in citrus groves
in Florida today, but so far as the Eloise Groves Association is concerned,
it is anticipated that zineb-sulfur sprays will be used for rust mite control
during August, September and" perhaps October, with sulfur dusts ap-
plied thereafter. Miticides for the control of purple mites or Texas citrus
mites will be used only where infestations become relatively heavy during
the fall months. Whether or not a routine dormant application will be
made will have to be determined as the result of mite infestations and
weather conditions during the late fall and early winter.
It is quite conceivable that citrus may well be placed on a program which
involves no more than 3 spray applications, and in many instances, only
two. It is quite possible that the elimination, or virtual elimination, of
sulfur from the spray program will result in lowered purple mite infesta-
tions. If this be true, it may be possible to go through the winter in many
groves without the necessity for purple mite control. This is perhaps wish-
ful thinking, but it further emphasizes the fact that careful checking of
groves during the fall and winter months will be essential in order to be
certain that neither six-spotted mites, purple mites, nor Texas citrus mites
are increasing.

Zineb was applied on groves belonging to Eloise Groves Association dur-
ing the 1957 and 1958 seasons in such a manner that comparisons on meth-
ods of application and dosage could be made.
(1) Zineb was found to be very effective for rust mite control, but
russeting did occur after the application of zineb in a few groves where
rust mites were not satisfactorily controlled.
(2) Dosages in old orange groves as low as 5 pounds per acre were found
to be quite effective.
(3) Excellent results were obtained with such dosages at post bloom

Vol. 42, No. 2

Griffiths: Results from Use of Zineb in Citrus Groves 91

time when applied with a double-headed Speed Sprayer driven at 21/2 miles
per hour.
(4) Failures of zineb in the summer scalicide in 1958 appear to be the
result of heavy rust mite populations at the time of spray. These infesta-
tions were related to the use of sulfur combinations at post bloom time.
None was recorded where zineb had been used at post bloom.
(5) It is suggested that combinations of zineb and wettable sulfur may
be practical for use at some times of the year on citrus.

Fisher, Fran E. 1957. A summer application of Zineb for the control
of citrus fruit russet. The Citrus Industry. 38(5): 5-6.
Johnson, R. D., John R. King, and J. J. McBride, Jr. 1957. Zineb controls
citrus rust mite. Proc. of the Fla. St. Hort. Soc. 70: 38-48.

Factories and Offices: TAMPA and FORT PIERCE, FLORIDA



92 The Florida Entomologist Vol. 42, No. 2

Book Reviews

pp., 135 figs. 15 pls., 1 map. MacMillan Co., New York. 1958. Price
The title of this book clearly indicates its coverage. The first part, de-
voted to collecting, tells where to look for insects, catching and trapping
them, keeping, breeding and rearing, and killing and temporarily preserv-
ing the catch. Part II gives instructions for preparing and mounting for
permanent preservation, examining insects in a collection and photography.
The last section concerns the study of insects, including the principles of
zoological classification and nomenclature, what are insects and their allies,
and how insects are identified. Further chapters discuss additional reading
in entomology and the description of new species.
The book is written for the adult who becomes interested in insects
or for students of entomology who are in the beginning stages of developing
a knowledge of this science. It has been carefully planned to answer the
needs of these two groups. Professionals may also find much of value in
the book, particularly for use as a ready source of general information
about insects.-L.B.

NESTS, by Ellis A. Hicks. 681 pp. Iowa State College Press, Ames.
The author states that "This work represents an attempt to assort and
consolidate information for the convenience of the user. As a result, the
approach is two-fold: (1) entomological, and (2) ornithological. These
two checklists are complimented by a third portion, a bibliography, which
is as inclusive as I could make it over a period of about four years."
This massive compilation is a most valuable asset to entomologists
studying relationships between birds and insects. For the beginner, here,
ready-made, is a starting point which will save him countless hours of
library study.-L.B.

92 The Florida Entomologist Vol. 42, No. 2

Book Reviews

pp., 135 figs. 15 pls., 1 map. MacMillan Co., New York. 1958. Price
The title of this book clearly indicates its coverage. The first part, de-
voted to collecting, tells where to look for insects, catching and trapping
them, keeping, breeding and rearing, and killing and temporarily preserv-
ing the catch. Part II gives instructions for preparing and mounting for
permanent preservation, examining insects in a collection and photography.
The last section concerns the study of insects, including the principles of
zoological classification and nomenclature, what are insects and their allies,
and how insects are identified. Further chapters discuss additional reading
in entomology and the description of new species.
The book is written for the adult who becomes interested in insects
or for students of entomology who are in the beginning stages of developing
a knowledge of this science. It has been carefully planned to answer the
needs of these two groups. Professionals may also find much of value in
the book, particularly for use as a ready source of general information
about insects.-L.B.

NESTS, by Ellis A. Hicks. 681 pp. Iowa State College Press, Ames.
The author states that "This work represents an attempt to assort and
consolidate information for the convenience of the user. As a result, the
approach is two-fold: (1) entomological, and (2) ornithological. These
two checklists are complimented by a third portion, a bibliography, which
is as inclusive as I could make it over a period of about four years."
This massive compilation is a most valuable asset to entomologists
studying relationships between birds and insects. For the beginner, here,
ready-made, is a starting point which will save him countless hours of
library study.-L.B.

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