Progress report on studies of Hypera brunneipennis (Boh.) in the Yuma Valley of Arizona

MISSING IMAGE

Material Information

Title:
Progress report on studies of Hypera brunneipennis (Boh.) in the Yuma Valley of Arizona
Physical Description:
Book
Creator:
McDuffie, William C
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine ( Washington, D.C )
Publication Date:

Record Information

Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030285301
oclc - 779489042
System ID:
AA00023064:00001

Table of Contents
    Introduction
        Page 1
    Extent of infestation
        Page 2
    Methods of spread
        Page 3
    The adult stage
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    The egg stage
        Page 9
    The larval stage
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
    The pupal stage
        Page 15
        Page 16
        Page 17
    Summary of seasonal history and host plants
        Page 18
    Parasites
        Page 19
    Economic importance
        Page 20
        Page 21
        Page 22
Full Text


5f\~V IA ~


E-551 U.S. September 1941
\ DEPARTMENT
FOF
AGRICULTURE
BUREAU OF
ENTOMOLOGY AND
rLANT QUARANTINE






PROGRESS REPORT ON STUDIES OF HYPERA BRUNNEIPENNIS (BOH.)i/
IN THE YUMA VALLEY OF ARIZONA

By William C. McDuffie,
Division of Cereal and Forage Insect Investigations



INTRODUCTION

On April 11, 1939, an insect believed to be the alfalfa weevil
Hypera postica (Gyll.) was discovered feeding on fenugreek (Trigonella
foenum-g9raeum L.) and alfalfa (Medicago sativa L.) near Yuma, Ariz., by
L. P. Wehrle and Robert Flack of the University of Arizona Agricultural
Experiment Station. Specimens submitted to the Bureau of Entomology and
Plant Quarantine were determined by L. L. Buchanan as Hypera brunneipennis
(Boh.), an insect occurring in Egypt, Ethiopia, and India but new to the
United States. Other than a brief summary of its habits and development in
Egypt by Willcocks, 2/ and the indication that it is a minor pest there on
berseem clover (Trifolium alexandrirum L.), nothing was recorded of this in-
sect in entomological literature.

A preliminary survey of the Yuma Valley by J. L. E. Lauderdale
and other Arizona State workers immediately following the discovery re-
vealed the infestation to be confined to the northeast portion of the tract.
Further investigation during the spring by J. C. Hamlin and W. C. McDuffie,
of the Bureau of Entomology and Plant Quarantine, and California State in-
spectors revealed an extension of the infestation about 1 mile north of
Yuma near Winterhaven, Imperial County, Calif. Other areas in California
and Arizona were examined, but no further infestations were found at that
time.


1/ Order Coleoptera, family Curculionidae.

2/ Willcocks, F. C. A Survey of the More Important Insects and
Mites of Egypt. Sultanic Agr. Soc., Tech. ec., Bul. No. 1. 1922. (See
pp. 43-44.)







-2-


In addition to fenugreek and alfalfa, Hyera brunneipennis was
found to be feeding on bur-clover (edicago hispida Gaertn.), hubam (annual
form of Melilotus alba Desr.), and sourclover (elilotus indica L.). The
sourclover is of general occurrence on uncultivated areas in the Yuma
Valley. Sufficient feeding occurred ci this plant to be classed as eccncm-
ic damage. Bur-clover in one small field was also heavily attacked. Noth-
ing definite concerning the suitability of alfalfa as a host was determined,
since the fiLst and a portion of the second crop had been harvested prior
to the discovery of the weevil, Consequently, the economic importance of
the weevil as a pest of alfalfa could not be evaluated until the advent of
another larval brood.

A preliminary investigation during the last days of April 1939
showed that larvae were scarce and mostly mature, cocoons containing pupae
were fairly numerous, and adults %%ere extremely abundant in the few heavily
infested spots. It was thus apparent that a brood was almost completed
and that little could be determined until another appeared. The immediate
consideration .'-as whether or not this would occur immediately and endanger
the valuable summer alfalfa seed crop Subsequent discovery that adults
were apparently aestivating, tcgetheor with studies showing the sexual im-
maturity of both malcs and females, appeared. t.0 indicate a period of inac-
tivity which might possibly exteid thogh the extreme sumwor heat into early
fall. Nevertheless, it vwas decided tc cciLinue the studies under the super-
vision of J. C. Hamiin as a part cf the Bureau's alfalfa ;eevil investiga-
tions, and for this purpose a sudstaticn of the Salt Lahe tLy Utah, office
of the Alfalfa ;'eil Investigat.on -was established at Yuma during June 1939
This paper is an account of the findings during the first year.

EXTENT OF INFESTATION

S, n Q79j i that Hypera brunne~ennis was confined to
the Y,, ma T, amaLi 'noj ec t ios-"ly to the northwest portion of the Yuma
Valley, YLLa County, 1iz in an area approximately miles long and 2 miles
wide. A smal oxte.sion of this area was foue immediately north of Yuma
on the Fot Indian rvao ea iterhaven, Imperial County, Calif.
Further scouting outward from these limits and i other suspected areas of
California ai Arizona gave negative results. Iowever, the :ear-cimpletion
of the larval brood cast doubt on the validity of the survey.

In 1940, as soon as the insect resumed activity in the fields, a
thorough survey vas conducted ly the Bureau of E tcmolcg) a.,d Plant Quaran-
tine in cocperation v'ith the Arizn4.a State Eitomologist office and the
Califor.Sia ita lpartme. tof Agriculture. Preliminary scouting during
Januarryai resulted in Fb L, :ekable extei:ison of the area known to
be infested ii the uma Valey a. I i th Cnli formia portion of the Ytma
Reclamation reject Two small ir s i ns weie also discovered in the Gila
Valley, uortheast aid east of Y, rv 1 hese infestations, however, were
within a radius of about 9 miles mrm the city.





-3-


A snail but important infestation was found on i U ni orsLty of
Arizona Date Experiment Farm neoir Tempe, Maricopa County, A K 1his in-
festation rs limited to a few square rods, and evadica on ieO ures were
applied by Lhe State Entomologist, Mr. J. L. E. Lauderdale. 11 irea *ithin
a 3-mile radius was placed under State quarantine.

Intensive scouting throughout southern and ce-ntra Cli %v ia and
southern Arizona failed to reveal other infestation is of H. I>u 'in nnis

METHODS OF SPREAD

The manner in which Hpera brunnjipennis was itroduced into the
United States is unknown but two possibilities have been adh :ced. These
are, first, through importation of date palm stock fic. Egyp so e 20 or
30 years ago, and second, through movement of produce or tran nts from
other portions of the United States or Mexico not now known uk he iinfested
The first possibility offers the most reasonable solution, since it is known
that large numbers of adults aestivate among the stubs of the old leaf stems
attached to the bases of date trees in the Yuma Valley. In vie,i of this fact
it seems probable that the infestation at Tempe, Ariz., can be attributed to
adults carried there with date palm offshoots from the Yuma Valley in 1937
or 1938. The principal evidence against H. brunneipennis having been intro-
duced through this medium is the fact that infestations have not been found
in other date-growing areas, some of which are older plantings than those of
the Yuma Valley, notably at Indio, Calif. There is, of course, a possibility
that the insect has been introduced into other areas but that certain factors
have prevented its establishment.

During the summer of 1939 a study was begun to determine the possi-
bility of weevil spread from the Yuma Valley through shipments of various
agricultural products. To date, only alfalfa seed and flax seed have been
studied thoroughly. The work on alfalfa seed indicated little danger of
weevil spread through shipment of this product. Factors supporting this
conclusion wcere (1) the apparent absence of weevils from alfalfa fields
during the seed harvest (July 15 to August 15), (2) the effeciveness of
threshing machines in destroying and preventing entrance i nto the seed of
artificially introduced weevils, (3) the effectiveness of recleaning in
eliminating all foreign material from the thresher-run seed and (4) the
unlikelihood of contamination from mill premises. A similar study of flax,
however, indicated a distinct possibility of weevil disse iin tion through
shipment of flax seed, since (1) weevils occur in most fieldc on volunteer
hosi plants (2) a few adults remain in fields during Jhe period of flax
harvest (late in May to July 1), and (3) flax threshing machines do not de-
stroy adults or prevent their entrance into the seed. Further ore, examina-
tion of seed from a representative flax field reveled the natural occur-
rence of an occasional adult. Biological studies to date in Yuna Valley
indicate that weevils which remain in fields as late as flax harvest are
abnormal and do not reproduce or survive the summer. If this is true there
apparently would be little danger of establishment resulting from their





-4-


accid 2' dstrihution into uninfsted areas, although there is no cer-
taity th.at e ould not recover and reproduce where the climate is more
tempera 1a i the Yuma Vall>, Tn this regard, however, it appears
likel, fiat t current requiremnnt tLat flax seed be shipped direct to the
mills Cor a.. eiatJ processing, o fumigeted when it is to be sold for seed,
would practically remove the possibility of weevils escaping.

The nost likely means of ,ex spread would be through shipment of
baled alalfa, hay and date palm of-shoots. However, fumigation of these is
required. A rity of other products shipped from Yuma Valley may possibly
spread th -;_, l hut none of these have been investigated as yet. Spread
may also occur 'rough the medium of vehicular traffic and through natural
dissemination, Iut nothing is definitely known of the possibilities in either
case.

THE ADULT STAGE

Description

The adult of Hypera brunneibennis (fig. 1, A and B) is a small snout
beetle approxLnately three-sixteenths of an inch in length. The newly
emerged weevil is bronze in color tut within a short while becomes brown.
The adult loses its covering of hairs and becomes shiny black when old.
In appearance K adult is very similar to the alfalfa weevil (H. postica),
but because of a slight difference Ln the contour of the back it is possible
to distinguish between the two species.

Emergence of Adults

The firs. new, adults during the 1940 season were collected from
sourclover o- -reh 13. The I'indin. of pupae 2 weeks before, however,
suggests that a f,% adults may ha merged slightly earlier. After March 13
the abunC foot o urclo on April 22, in spite of the fact that small numbers began
co migrate.. from th field to aesti'vation quarters aLout April 1. On April 29
adults wer equally abundant, but the scarcity of cocoons and larvae showed
clearly that production of adults %as virtually completed. Therefore, it is
indicated t1a Che haviest emege. c of new adults occurred during the 6-
week period from mid-March to late in April.

Post-emergence Activity of Adults

Afttr unergence from cocoons, new adults fed heavily on the nearest
aailable succulent lkguminous host, principally on the leaves. Large num-
bers of adults partially or completely defoliated some plants and also fed
to some extent on the epidermis of stems. The post-emorgence feeding period
lasted from 2 to 3 weeks. Feeding ceased rather abruptly, and most adults
migrated from fields in search of places for aestivation, where they remained
inactive throughout the summer and early fall months.





-5-


A few adults fed by day, but the heaviest feeding o ured at night,
especially during the late spring when daily maxiilu-n te p -,tur o
or exceeded 100 F. During such teirperatures aduls pr,(ee, d to ren
under cover on or near the ground in comparative inactivity ,i the cover
in feeding areas was inadequate, adults concentrated inearhy gra uaeas or
in soil cracks during the day and returned at night to resu c fncding.

An occasional adult aestivated in feeding are h d ground
cover existed, but virtually Lll left these areas to c gr( to n tions
affording more suitable protection. A fe' indiviK Iid t tive in
fields and could be swept from then at night until .he bo harvest loe in
June. Thereafter, neither sweeping nor examination of deri S fro fields
revealed adults.

The few weevils remaining active in the field developed e some extent, some of the females attaining the state of dexeloping ova and
even full-sized eggs. Dissection of these adults revealed apparent dis-
integration of the sexual system, and apparently aiLl died, since none was
found to be intermixed with aestivating weevils. moreover, the practice of
abandoning alfalfa fields, with consequent absence of succulent food and
cover during the heat of the summer and early fall months, i Iitates against
survival of these adults. Two seasons' study of these 1......viduals
shows conclusively that they are unii:portant under Yuma Valjey conditions,

Abundance of Adults

Late in April in 1939, extremely large numbers of culta congregated
by day in grassy borders surrounding alfalfa varietal rolrs on the University
of Arizona Valley Experiment Farm at Yuma. Considerable num'bes also c-
mained hidden about the base of alfalfa crowns. At ni4h-, alfalfa plants
nearest to grassy areas were literally covered by adults, soie plants having
an estimated 200 to 400 on them, which resulted in rapid CefoliaticnSamples
from a sourclover breeding area in a pecan grove on April 30 co-trained an
average of 72 adults per square foot, Adults crawled pro~ise i usj on the
ground and even in the trees. A nearby Bermuda grass l&n, wdith a sparse
mixture of sourclover, contained 13 adults per square foot, A*dults were
fairly numerous on the University of Arizona Mesa E:xperient Frar' and the
Oasis Ranch near the city lihiits of Yuma, but otherwise were scarce through-
out the infested area. In alfalfa fields adjacent to the most heavily in-
fested areas comparatively few adults existed. This was attributed, in part
at least, to heavy migration following earlier harvest of the first hay crop.

In 1940 the production of adults was greatly curtailed because
of' a high mortalityy of the larvae. By way of comparison \ith P 39, con-
tinuous sampling of the most heavily infested sourolover breeding area on
the Arizona Valley Experisent Farm showed a peak abuidance of only 4 adults
per square foot. Samples from the most favorable cover ar nr ccre n saoved
a peak of olly 7 per square foot. in alfalfa varieta_ piots and nearby
alfalfa fields adults were actually difficult to collect by s,-ecping alethods.





-6-


It v-as Ys Iea -l- -- onstrat.,d hat fh a Kucn o- -ats as Euch l s
than i 19 r'd hat the parent rculaicn for 141 will he O1nS-dc ?'1y
less th u i 1940 hen it ,'as cvs dere ec scal. -act or irolced in
this dcclii o aouIt populations a elie Co h> >ee w ath-r unsuit-
able for he deelopment of the larvae and parasitiation,

Aestivation of Adults


follow.A ;
eai~ >

~.xo '


e a n

: us,'o h mo th D : g! a e n

dou' ss approximate e du-ratioi Q Lte a o.. LS


of gro n u ...a..... ..
tions a g .. A' also ei.. < c r: vbs
of old ." -a u a > oil
passed the and fall in h a -
in heaiy ': ci nrcas, and ii g'-'iss
vived in I h I~ -ations. Noe
fence costs or < the cracks a r. c o o arm


W. "
ration >hc:
ficaio iof ti
moisture or
for others.

Dtio

C ond iion


va.~ e ~ cc 'a. ~''. ~ ~. .

r~. ~. cauecU aCi~lt~ u & a.~ ~ci. a


~ I I''Ou 0 ~ ~ AH-
1 -
-A .iaa b ul ~


C -.

'-4

1~"
'1 -ir-
-cc
1-.


.2


~A jj .. -~ cain s~n:oh


1 -
4 --
yUl'


Studies of Sexual Develoi:nt


tO oji A


tion a.
maturity.


1- 1i 4


a
(A ~.

1,
v.~.aP ~n


H
1 F ~i. I


I. 0 -1
-ll. icalls a. ai


. '] <0~l t I = '.:<
4- .x "' P. cuT cii




C '

U ZL Li~ k( L LL


k 1 :1


To
.210
a-
~~1





-7-


of aestivating females lagged considerably behind that of' males, s1in
but little ovarian development until mid-November. Segmentation vas oiserved
on November 24 and developing ova on December 7, but none attained the full-
sized egg stage by December 16, the date of final dissections. It was thus
indicated that females migrate to fields before attaining complete sexual
maturity. None of the aestivating females was fertilized, indicating that
mating does not occur until after migration to fields,

The initial collection from fields on November 24 of adults recently
emerged from aestivation revealed some of the females with full-sized eggs
and fertilized. All field-collected females were fully mature by December
30 and many were undoubtedly ovipositing. Almost one-third of the males in
the field were fully mature on November 24 and all were fully mature by
December 16. It is believed that the full maturity of all adults in the
field indicated that emergence from aestivation was complete.

Night collections showed that a few adults of the current season
remained active in the fields until late in June and developed sexually, a
few males attaining full maturity. Occasional fertilization was attributed
to the presence of old males, since new ones had not attained full maturity,
although occasionally one exhibited sperm in the testes. These developing
adults appeared to be abnormal and exhibited signs of internal discoloration
and deterioration. Failure to encounter these during the summer and early
fall, either in fields or in the course of regular dissections, clearly
indicated that these developing adults die.

Preoviposition Period

The preoviposition period of Hypera brunneipennis is equal to the
length of the aestivation period plus a 2- to 4-week post-aestivation feeding
and mating period. Calculated in this manner, the preoviposition period is
8 to 81 months.

Oviposition

Ecological samplings from an alfalfa field on December 12 failed
to reveal eggs, but oviposition is believed to have begun about December 17
the date of initial oviposition in laboratory cages, Oviposition was well
under way by January 3 and was extremely heavy during January and the first
half of February. The peak abundance -f P5 eggs per square foot appeared
on February 5. Thereafter the egg population declined and remained at a
low level until none were found on or after April 2. It is therefore indi-
cated that the oviposition period in the alfalfa study field this season was
approximately 3 months.

Similar studies in sourclover were not begun until late in the season,
but it is unlikely that oviposition began on this host until about mid-Janu-
ary, since it failed to obtain an appreciable growth before that time.
Initial studies on March 13 showed 74 eggs per square foot, but thereafter






-8-


the nu-ber declined and remained at a low level. A few clusters of eggs
were still present as late as May 6, the date of the final sampling. It
was thus indicated that oviposition in sourclover growths may continue a
month or more longer than in alfalfa.

Individual oviposition records were not attempted, but average figures
were obtained on three hosts by establishing bulk cages, each containing
10 pairs of adults. The cages ,ere ordinary jelly glasses with a small
amount of soil packed in their bottoms and with the original tin lids per-
forated to provide adequate fresh air. Fresh food and new dry stems were
supplied on alternate days when counts were made. Adults confined on al-
falfa were collected from aestivation early in December and records are com-
plete Cages containing huban or sourclover were not established until Janu-
ary 4, when these plants first beca._e available. Adults for these were swept
fro r alfalfa, 'here they had alreadJ fed and oviposited for approximately
2 eeks. Consequently oviposition records for adults confined on these
foods are not co,-1.plete. The fact that these plants were not available to
adults e erging from aestivation renders it certain that all adults fed
initially on alfalfa and later dispersed to such other hosts as became
available.

Oviposition in two alfalfa cages lasted for 4 and 4]1 months, respec-
tive-,, after initial eggs were deposited on Decenwber 19. Assuming that
oviposition of the adults confined on hubam and sourclover began at the same
time, the oviposition period for huba. cages was 3 and 5 months and for
sourclover 3 and 31 months. If calculated from the date of establishment,
the oviposition period on both hubar- and sourclover would be approximately
2 weeks shorter. Results indicate some slight differences in the duration
of the oviposition period on various hosts, but the evidence is insufficient
to warrant a final conclusion in this regard. On the basis of only one sea-
son's work it was indicated that huba., and sourclover promoted equally
heavy oviposition and alfalfa significantly less, in spite of the fact that
records on the two first-named hosts were incomplete Data are given in
table 1.
Postoviposition Period

~ost caged females died before their complements of eggs were com-
pletely exhausted, and no spent fe" ales have yet been encountered in dis-
sections of field-collected adults. In oviposition cages, however, a few
females survived from 2 days to more than a month after final oviposition.

Longevity of Adults

A.dult3 began to die shortly after e..ergence from aestivation, but
field ,_ cIie tudies indicjted that .ortality was of small consequence
until r-iiy ii ar.h, ,ortali oa old adults was virtually complete by
April i. but a -;v individual. 13Urvyived throughout May. In 1939 one was
encountered as late as June 6, It was thus indicated that adults may




-9-


Table l.--Oviposition of Hfpera brunneipennis under insectary conditions
on alfalfa, hubam, and sourclover. Yuma, Ariz., December
1939 to May 1940

Approximate Number of egs_posited
Date oviposition Mean eggs Mean
Cage established period (months) Total per female average

Alfalfa Dec. 9 4 5,810 605 l/
do. do, 41 5,158 580 1/ 593

Hubam 2/ Jan. 4 5 7,729 1,066
do. do. 3 3,602 563 815

Sourclover 2/ do. 31 5,292 864
do. do. 3 5,202 724 794

l/ A mean number of 105.8 eggs per female was deposited on alfalfa
before cages on other hosts were established.

2/ Adults used were already ovipositing when these cages were es-
tablished.


aestivate for approximately 8 months, emerge, and survive for a further per-
iod of 5 or 6 months in the field, a total period of some 13 to 14 months.
The majority of adults apparently live from 10 to 11 months.

Adult Dissemination

Adults possess well-developed wings, but none have been observed in
flight in the field or captured on tanglefoot screens. Attempts to force
flight were unsuccessful. Adults are capable of flight, however, this having
been observed on several occasions in the laboratory. Nothing is known con-
cerning the frequency, the time, or the distance of adult flight in the
field, and no evaluation of its importance in dissemination and spread can
as yet be made. There was considerable local movement of adults by crawling,
but it is unlikely that any great distances are thus covered. especially
after the adults have established themselves satisfactorily in fields.

THE EGG STAGE

Description

The freshly deposited egg (fig. 1, C) is bright lemon yellow but be-
comes dusky or dark in appearance, usually in about a week. It is oval in
shape, averaging 0.63 mm. in length and 0.40 mm. in width; the length ranges
from 0.54 to 0.70 mm. and the width from 0.36 to 0.44 mm.





- 10 -


Where Eggs Are Laid

Egg laying in alfalfa fields was confined almost entirely to dead,
dry alfalfa stems composing the surface litter. Only a few clusters of eggs
were encountered in living alfalfa stems or in living or dead grass stems.
About 95 percent were deposited in small, dry, easily punctured stems 1.5 mm.
and less in diameter. Eggs were deposited in clusters ranging in size from
1 to 46 but comparatively few contained more than 25. The average cluster
in dry stems of alfalfa fields contained 14.3 eggs.

Early egg laying in sourclover was also confined mostly to dead stems,
but by early March the majority wele contained in the growing stems, indi-
cating a marked difference in adult reaction to the two hosts. The fact that
virtually no eggs were found in stems of growing alfalfa suggests the possi-
bility that this plant is an unsuitable host in this respect. This ap-
parent reaction of the ovipositing adults to sourclover is closely analogous
to the oviposition habits of Hypera postica on alfalfa in Utah and other
States.

Incubation Period

The incubation period was determined under insectary conditions
where temperatures closely approximated those in the field. Eggs were ob-
tained from oviposition cages and incubated in salve jars on moist blotting
paper. Moisture was added in small amounts as needed until hatching ceased.
Except in a few instances, eggs for this study were obtained only from
adults caged on alfalfa.

During nost of January, when the prevailing mean cutdolor temperatures
were about 540 F., incubation required 20 to 22 days, but slightly warmer
weather late in the month and eaIy in February shortened the time to 16 to
19 days. By early March the incubaticn period had shortened to about 10 days
and by early April, with outdoor minan temperatures of about 750 F., it was
only about 6 days. Incubation of several series of eggs late in the season
from alfalfa, sourclover, and hubam indicated that the host plant of the
parent adult had no significant bearing upon either the incubation period
or the viability of eggs. Data on the incubation period are presented in
table 2.

THE LARVAL STAGE

Information concerniig the larval s (ae (fig. ), D) was obtained
through rneasdreuets of larval iead si'es, laboratory rearings, and periodic
ecological sa plin.gs of alfalfa fields aid sourclover patches, supplemented
by general field observations.

Description of the Larva

Keasu eyoe of hoad s izes o .4' ,itely showed that HP'jera brunneipennis
has four larval instars. Small numbers of measurements at intervals through-
out thQ season showed no variation either in the number or the head size of




- 11 -


Table 2.--Approximate duration of the incubation period of eggs o;
Hypera brunneipennis under insectary conditions, Yuma,
Ariz., January to May 1940

Incubation eiod a
Date deposited Range Average

Dec. 30 Jan. 2 21 24 21.2
Jan. 6 Jan. 8 21 23 21.5
Jan. 8 Jan. 10 20 21 20.1
Jan. 12 Jan. 14 22 22,0
Jan. 20 Jan. 22 18 19 18.2
Jan. 26 Jan. 29 14 19 15.8
Feb. 2 Feb. 5 19 22 19.4
Feb. 5 Feb. 7 17 21 18,2
Feb. 7 Feb. 9 17 21 18.3
Feb. 10 Feb. 12 16 17 16.2
Feb. 12 Feb. 14 15 21 15.9
Feb. 16 Feb. 17 13 16 14.1
Feb. 19 Feb. 21 11 15 11,9
Feb. 24 Feb. 26 10 14 11,8
Feb. 26 Feb. 28 11 13 11 5
Mar. 2 Mar. 4 11 15 11 7
Mar. 6 Mar. 8 11 13 114
Mar. 8 Mar. 11 9 12 10,5
Do. 9 12 10.0
Do. 9 12 10.3
Mar. 15 Mar. 18 8 9 8.8
Do. 8 9 8.8
Do. 8 9 8.9
Apr. 10 Apr. 12 4 7 5.1

larval instars. Larvae of each stage vary greatly in body size and there is
an overlapping between successive stages which renders classification on
this basis uncertain. Results of head measurements of 100 specimens of each
instar are shown in table 3.

Table 3.--Measurement of larval head sizes to determine number of
instars, of Hypera brunneiennis, Yuma, Ariz., 1940

Larval Width of head capsules {mm.)
Number measured instar Range Average

100 First 0.195 210 0.203
100 Second .260 .300 285
100 Third .395 .445 .418
100 Fourth .565 .650 607









The ne;ly hatched first-stage larva is about one thirty-second of an
nch in _e~g.h The body color varies from yellowish to light gray and the
head is black. After feeding for a time the larva increases in size and the
body usually assumes a somewhat dingy-gray color; the head remains black.

I-e nately upon molting to the second stage the larval head is yel-
low, as it is after succeeding molts, but soon becomes dark. The body is
dingy gray, but a few individuals acquire a faint greenish tinge immediately
before molting to the third stage.

The head of the third-stage larva is mostly black but with traces of
brown about the center. Its body is light green with a readily visible white
stripe down the middle of the back.

The head capsule of the fourth-stage larva is almost entirely brown
but with noticeable darkness about the edges, especially posteriorly. The
body is light green with a broad white stripe down the middle of the back
paralleled by smaller but distinct white stripes on each side. A limited
number of measurements showed a range in body length from one-fourth inch to
almost oi.e-half inch; the average body length was four-tenths of an inch.

Lar\ae of' Hvpera brunneipennis are similar to comparable stages of
H. Lostica, aeid no distinguishing characteristics were discovered.

Feeding Habits of Larvae

Newly hatched larvae preferred the tenderest portions of host plants,
usually heing Concentrated in the buds or stem tips and sheaths at the base
of stems. Mony small larvae buried themselves in these tissues and remained
hidden for short periods while feeding. Second-stage larvae fed in a similar
manner but were usually more easily observed than the smaller first-stage
larvae. Conparatively few of either stage could be collected by net-sweeping
of plants.

Lalger third and fourth instars also fed upon the tender portions of
plants but i. t heavily upon the open leaves. Alfalfa leaves were skeleton-
ized by initesve feeding, leavii.g only the principal leaf veirs and some-
tines pote s f the lower epidermis. Larger larvae, however, feeding upon
the thicV'er ves of sourclover aid hubam, tended to consume all the leaf
tissues, r _aEig clean holes or completely removing portions of the leaves,
thu.; gi ii iad appearance to Lhe plant. In general, larvae concentrate
first c the uii ot portions of plants and move downward as the foliage
is destroy~ : he manner f feeding and damage inflicted H ~era brun-
neipenni appears to be identical w-ith the alfalfa weevil (H. postica) on
alfalfa.

1 2v e tha becci:e diis o d .e from plai.ts readily ascend and feed upon
the riearest ,aiu;h host plat. They are capable of crawling short dis-
tarices oxer dy exp sed soil, if not too hot, and also over soil following
irrigti h ;rv e nave been observed actually to remain in water for short
period 1 2 a.e its subsidence, t ascend and resume feeding on the near-
est host plant.





- 13 -


Duration of 1 I a:1a Sta I


Duration of the
determined by bulk ae r
conditions where tempa n
field. Each rearing os)1 <
30 to 50 newly hatched
son. Cages used were c
tin, paper in the bo
evaporation and diry -,
and fresh food was suC pl0.

I n i t ia 1 r e s u I Ls
1 month, developing s] 1
period decreaod con
vanced, being onl' Ae,
rearing larvae rec y
sourclover or huh ic, h

Data. showing he different hosts are gi.v. n


tae 01)
1101i
10r *2 to


jelly1l :'

Koo, 1,1 :


(I P


o1 e ,
tly lIs ti fT t
ared about eq Il

'2, ti\e (lOVEl
ble 4


Larfv -a A.nda ice aid Develojicn


The first newly
but very few were pre
eggs gave promise of (
and continued ovipositio*
with that of eggs. 1
only a small fraction
ceeding stages. pp I
and development o al
were observed fol]ovinS
January, and their eh
vent of favorable
lation again decli.nIed f{
February and continued to
due in part to a decline
tality. The fact that !-
the advent of warni spr .
alfalfa as a larval host.


Jar ao
'ml lae an J .nIa:l ; 1

1) s SOr uever t( [;i
21[ f"l0 I' f P 0

a:,o~ to ish se(o U
}S, 0o1e factor o-r-

a piod of frosiy 111?
attributed o 1 .
2d]a\ae c-uickl, ,ou1
o],1 : 1 a secoe a ol<.

PC,) O option, :
Ia <1 mortsl' .
1 f t @ s 0r0?g ( J


Information on 'he ' .ance ard dep
was not obtained during n since ts,
growth until late in -l o- Early in
revealed larvae to l- ous in so- l o I
and this was even morc p l n
affected the populatio. n A same manner sn






- 14-


Table 4.--Duration of the larval stage of Hypera brunneipennis on
alfalfa, hubam, and sourclover, Yuma, Ariz., 1940

_LenZth of larval stage (days)
Date Mean days in states

Food started Ist 2nd 3rd 4th Range Mean

Alfalfa 1/29 6.6 8.0 9.8 6.6 30-32 31.0
Hubam 1/30 7.0 10.1 8.1 7.2 30-40 32.4
Sourclover 1/30 9.3 8.2 7.6 7.6 29-36 32.7

Alfalfa 2/12 9.4 4.1 3.8 6.2 23-27 23.5
Hubam 2/12 10.0 5.6 5.8 7.0 27-32 28.4
Sourclover 2/12 9.7 5.2 5.1 6.9 23-24 26.9

Alfalfa 2/24 3.6 4.3 4.3 7.8 20-22 20.0
Hubam 4j ---..---. ........
Sourclover 2/25 5.6 5.0 6.8 7.7 21-29 25.1

Alfalfa 3/2 4.0 3.8 6.4 5.9 19-21 20,1
Hubam 3/2 5.9 5.5 5.7 5.0 21-27 22.1
Sourclover 3/2 5.3 7.4 2/ --- ---

Alfalfa 3/10 6.8 4.4 4.4 5.3 19-25 20.9
Hubam 3/10 7.0 4.2 4.6 6.1 21-23 21.9
Sourclover 3/10 7.8 4.9 4.2 2/ ---

Alfalfa 3/21 3.2 3.5 4.3 6.3 17-21 17.3
Hubam 3/2] 5.7 5.2 5.4 5.1 19-23 21.4
Sourclover 3/21 4,9 4.2 4.2 6.4 17-23 19.7

I/No cage established.
2/Cage closed because of complete mortality,


v .JU~,,hat bsaI by greater ce of larvae resulting from a larger
pare. t adult population. Ecological studies begun in sourclover on March 13
r-eveale a sizeable larval p:pulatci. and an abundance of eggs, indicating
a tiii ued iiiciease of larvae, Hcwever, the larval population failed to
ii-.rease and sox. began to decline. with relatively few developing to ma-
turity. Comparison cf data on the two hosts indicated that sourclover was a
more suitable host than alfalfa, but even on sourclover only a minor portion
of the population developed to the adult stage. Consequently this plant must
be considered only as the most satisfactory of the available hosts. Com-
parative data on the abundance and development of larvae on alfalfa and sour-
clover are presented in table 5.





- 15 -


Table 5.--Comparative larval abundance and development by stages of
Hypera brunneipennis in alfalfa and sourclover,
Yuma, Ariz., 1940


Number of larvae
Instar
2nd 3rd


Field






"Date
Grove"
alfalfa











"Pecan
Grove"
sour
clover
area


Jan.
Jan.
Jan
Jan.
Jan.
Feb.
Feb.
Feb.
Mar.
Mar
Mar
Apr.
Apr.

Mar
Mar.
Mar.
Apr
Apr
Apr
Apr
Apr.
May


per square foot


Date
sampled


I/Growth clipped
larvae.


on April 3. causing considerable mortality of immature


THE PUPAL STAGE

The pupal stage (fig. 1, E) is passed in thin, white, netlike cocoons,
usually oval in shape. Mature larvae usually attach their cocoons to the
growing leaves of host plants. One or more leaves may be utilized to pro-
vide satisfactory protection during this state of inactivity. A considerable
number are also attached to dead leaves and stems above the ground. Com-
paratively few are spun in the surface litter or on the bare soil. The
spinning of cocoons above the ground is not a seasonal habit but a charac-
teristic of the species. In this respect Hypera brunneijpennis differs from
the alfalfa weevil (H. postica), which spins most of its cocoons in the sur-
face litter.

Shortly after spinning, the larva curls up and remains relatively in-
active during a short period in which it gradually transforms into a pupa.



STATE P gT BO


ist


4th




0
0
0
0
0
0
0.13
0.38
0.13
0
0.13

5.43
3.57
3.29
7.00
4.13
0.25
0
0
0


0
2.00
1.50
5.13
6.25
4.25
4.00
0.88
0.13
0
0.25

5.43
3.86
6.86
3.29
0.38
0
0
0
0


0
0
0
0
0.75
0.25
0.25
0.50
0.25
0. 13
0

4.43
2.71
4.86
4.57
0.63
0
0
0
0


0.75
16.00
18.50
33.13
25.63
19.13
3.88
9.25
2.25
1.75
0.25

9.86
16.00
9.14
7.00
0.13
0
0
0
0


Total


0.75
18.00
20,00
38.25
32-63
23.63
8.25
11.00
2.75
1.88
0.63

25.14
26.13
24.14
21.86
5.25
0.25
0
0
0


13
20
27
2
10 l/
16
22
29
6






- 16 -


The newly formed pupa is usually light green but as development progresses
it gradually assumes the structure and light-bronze color of the adult. The
exoskeleton of the newly formed adult is thin and soft, but in a few days it
hardens and the adult is able to emerge from the cocoon.

Duration of the Pupal Stage

The duration of the prepupal and pupal periods was determined by con-
tinuing larval rearing cages until the emergence of adults.

During the early part of March the length of the prepupal period ranged
from 4 to 1 days and averaged 4.0, 4.3, and 4.9 days, respectively, for
larvae reared on sourclover, hubam., and alfalfa. The duration of the pupal
stage on these hosts ranged from 12 to 21 days and averaged 9.0, 11.1, and
10.2 & s, rspcctively. The length of the enTire pupal period on sourclover,
huham, and al'alfa, respectively, was 13.0, 15.3, and 15.1 :ays. Both the pre-
pupal and pupal stages required fewer days during the remainder of March,
and there ,as no significant difference attributable to the larval food.
The final rcaring begun early in April revealed a marked shortening of the
prepupal and pupal stages, with the entire pupal period requiring only 6.2
to 6.8 d.a s. Adults remained in cocoons 2 to 5 days before emerging but
most of them emerged in 2 to 3 days.

Data on the approximate duration of the pupal period are shown in
table 6.

Abundance and Development in the Field

Ecological studies in an infested alfalfa field throughout the 1940
season failed to reveal a cocoon containing either a larva or pupa, and
only one empty cocoon was encountered Many other fields were examined,, but
in only a few was an occasional cocoon observed. This clearly indicated
that very few larvae survived and developed to maturity in alfalfa.

Similar studies in a heavily infested sourclover area showed that
only a small proportion of a sizeable larval population survived to spin
cocoons. Furthermore, only a minor portion of cocooned individuals reached
the adult stage. This condition also prevailed in the many other sourclover
areas ots.rvcd. A portion of the mortality within cocoons probably was
attributable to the same factor or factors that affected the larval popu-
lat~ic Thre we.ro, however, several known factors involved, principally
xpo Sure Lo A sun. and parasites. The combined effect of the various
f'actoris n in- abundance and survival of pupae is shown by the date
given in table 7.






- 17-


Table 6.--Duration of the pupal period of larvae of Hyp -, f r i nieiennLs
reared on alfalfa, hubam, and sourclover, Yuma, Ariz 1940


Lengt


Larval
food
Al fal fa
Hubam
Sourcluver

Alfalfa
Hubam
Sourclover

Alfalfa
Hubami
Sourclover

Alfalfa
Hubam
Sourclover

Alfalfa
Hubam
Sourclover2

Alfalfa
Hubam
Sourclover


Date
first cocoon
2/28
2/29
2/28


3/6
3/10
3/6

3/15

3/17

3/21
3/23


3/29
3/31


4/7
4/9
4/7


Preppal stage
Range Mean


4-11
4-15
4-11

4-9
5-9
4-15

2-8

4-12

2-6
2-6


4-9
2-4


4-6
2-6
2-6


4.9
4.2
4.0

4.0
5.2
4.2

3,7

2.1

2.5
3.1


4.1
3.4


3.9
1.8
2.3


_period_(ayIL
Pupa Ist ae


Range

9-14
11-17
8-16

9-Il
6-10
9-15

6-10

6-11

6-12
6-13


7-9
7-


2-7
4-9
4-9


102
i! .0
90


9.9
6.5
76

5.6

6.2

6.6
7,7


6 4
6.3


2.3
5.0
4.0


i/No cage established


2/Larvae died before cocooning


Table 7.--Abundance and development of H vera brunneipennis coons per
square foot on sourclover, showing effect of mortality upon
production of adults, Yuma, Ariz., March to May. 1940


Contents living
Percent
Total pupated


3.71
8.71
3.29
3.29
7.00
5.38
0.38
0
0


50.00
66.18
39.39
30.77
73.21
88.37
100.00


Contents
dead'

0.14
1.00
1.43
0.57
6.63
11.00
4.25
2.25
0.29


Total
(all)

3.85
9.71
4.72
3.86
13.63
16.38
4.63
2.25
0.29


Number of
new adults
emerged

0.29
0.71
1 14
1 57
2,00
2.75
4.00
3.88
1.00


l/Total dead from all mortality factors.
_Clipping growth on April 3 hastened cocooning


of many maturing larvae.


13-18
15-21
12-20

1,3-15
11-15
13-19

8-1

10-15

8-14
S8-15



11-13
9-


Mean

15.1
15.3
13.0

13.9
11.7
11.8

9.3

8.3

9.1
10.8


10.5
9.7


6-Il
6-11
6-11


6.2
6.8
6.3


Date
sampled


iar
Mar
Mar
Apr
Apr.
Ap~r.
Apr
Apr
May


13
20
27
2
102
16
22
29
6






- 18 -


SUMMARY OF SEASONAL HISTORY

Except for a few individuals that remained active late in May and in
June, Hera brunneirennis adults were in aestivation from the middle of
May until late in November, 1939, under the loose bark of growing trees,
among tVe 2L~d leaf stubs about the bases of date palms, and to a lesser
extent in he soil and debris abouI the bases of trees, in heavily weeded
areas, and in grassy ditch banks Emer'gence of adults from aestivation was
gradual and was completed by January 1, 1940., the greatest exodus having
occurred during the first half of December.

Oviposition began in alfalfa fields about the middle of December,
was at its height during January and early in February, and gradually de-
clined to insignificance in early April Eggs were abundant in sourclover
as late as the middle of March and declined thereafter, although a few were
still present as late as May 6. In alfalfa fields eggs were deposited al-
most entirely in pieces of dead, dry, easily punctured alfalfa stems in the
surface litter in clusters of 1 to 46, In sourclover patches early ovipo-
sition was also mostly confined to litter stems, but by the middle of March
most of the eggs were contained in the living stems, indicating a marked dif-
ference in the adult reaction toward sourclover and alfalfa. During the cool
weather of January eggs hatched in about 21 days, but as the weather became
warmer the time gradually shortened to only 5 or 6 days in early April.

The larvae matured in 26 to 32 days during the winter months and in
17 to 22 aps during March and early April. The mortality of larvae feeding
on sourclover in the field was very high and almost complete on alfalfa,
relatively few finally attaining maturity. By the middle of April very few
larvae remained either on sourclover or alfalfa.

A fIe' larvae matured and forced cocoons as early as the end of Febru-
ary, but th majority matured and formed cocoons during the latter half of
March and early April. The pupal period lasted about 15 days during early
March but gradually shortened to 6 or 7 days during April.

-he t ne," adults were o&ser,.d on March 13, and emergence was ap-
pareiA com !lt Ly the end of Ap'l, the greatest number having emerged
from It-: hoKi-April E, th i ddl of May practically all the new-
je/3 n ( K .s hd completed _ejing and gone into aestivation. Only
one generation. occurred during the year.

HOST PLANTS

of'ul H ,) uineiue S have 1 cjn observed to feed
on ali (fXi"iL s'._t ixvt), huham (annual form of Mlilotus alba), bur-
cloy .r (M{ Cj~ Vo id'j .), fcn ugre (TT i nla foenurr-Fraecum) and sour-
clovCr (M in ica). Of' plants onl alfalfa is of economic im-
portance .. fl Yuma area, it beit, he pincipal forage crop. Hubam and
source o ar occasionally planted an greenQmanure crops but are mostly
volunteer rus and pecan gre and ulong dit ches and rds ides, Bur-
clover exist oi]y in small amouints, moatl_, in lawns. To date the growth of
fenugreeti ha'I been limited to a f(w experimental patches.




- 19 -


Other legumes, such as sesb ;)rj nSeshani mirci i) an ca (Cj-
amopsis tetragonoloba) are widely grown as gree. -r," ure crops durun 1he
summer months when the weevil is aestivating. and their status as hosts is
not known.

Triplicate plantings of ibe following 10 legumies were made with v
to learning something about host range and preference; alfalfa (MeL ago
sativa), bur-clover (MLorlc.ro hubam (annual fo rm of Melilotut' aIla)
sorrc I'er (Meci lotus ii-ndira) bereem clover (T rfolium a!ex an in m
whi te Dutch clover (Tr i foli um -I ha fenugreek (Tr; oLella foenum-0r~em)
vetch (Vicia sp.), Canadian field pcas (Pisum sp.), in welga p {Lhy
sp.). Hypera brunneipennis ad'its congregated 1aturally in these plots
early in the season, making artificial infestation ui. .ecessary,

Larvae fed to some eXv!e iaci- <1 these p of pia)ts except
wedge peas and Canadian field pe s The total absence of" feeding n, tlose
p 2a'r s indicated that peas and poe.. >1 y beans 'ay -t be svitabie ho a
On the other hand, it appeared that. tae species c,, I re success y on
alfalfa,. the clovers, ve, ch, and fe' groek. More complete tests v'. oiher
legumes would doubtless reveal ms'u: that would serve as hosts, at .s
to a limited extent.

Larvae failed to survive nd develop in lbeis on any of these 10
legumes, thus obscuring any real differences in attractiveness. Farl]. in
the season larvae were most easier ?nund on alfafa, but later this host
harbored no more larvae than the clovers, and feeding on all was entirely
negligible. Late in the season a large number of larvae were introduced in
an effort to obtain definite indications as to the preferred host, but most
of them apparently died within a short time.

Under natural fiela condition -,:eevi! populations were considerably
larger on sourclover than on alfalfa, but only a mJror portion of the larvae
survived to become adults, Theref' scurclover shvu d not be considered
a perfect host but rather the most suitable of those available, Fu.,rther
study must be given this phase before final conclusions can be made.

PARASITES

Incubation of Hypera brunnei)eunis eggs from field samples and 1Inde-
pendent field collections failed to rpveal a single parasite of this stage
Parasites were reared from both t1-,e larval and pupal stages These incled
at least one dipterous and three hymneropterous species, and positive identi-
fication of the quantity of material collected may reveal several others.
Some of them may prove to be secondary parasites.

Late in March and early in April parasites appeared to be of consider-
able importance, as almost one-third the cocooned individuals from sour-
clover samples were affected Thereafter, however, the combined effective-
ness of parasites declined to a relatvely unimportant level. Larval para-
sitization was at all times negligible and confined to maturing indivi luals.
These findings indicate that parasites may become a potent factor in cur-
tailing the production of adults, but further studies must be made before
their importance can be established conclusively.





20 -

ECONOMIC IMPORTANCE

Populations of 1ypera brunneipennis on alfalfa during the 1940 season
were insufficient to inflict material injury to a single field. In no
instance did feeding become noticeable or even approach damaging proportions.
Larvae were fairly abundant and caused slight injury only in a few small
patches of sourclover, a plant of no economic importance in the Yuma Valley
of Arizona. This indicated that the insect is capable of inflicting damage
under certain conditions, but too little is yet known of its potentialities
to warrant a conclusion as to its status as an economic insect. All that can
be said at this time is that winter and spring pasturing and cutting of
alfalfa as regularly practiced in the Yuma Valley apparently would tend to
prevent this insect from becoming a serious pest of this crop in that lo-
cality.































C






D ,.











Figure .-Hviera bruei nts: A, Adult beetle, dorsal view; B,
adult, lateral view; Cs eg; Ds larva, full-ro, lateral view;

E, pupa, ventral view. All greatly enlarged.





UNIVERSITY OF FLORIDA



1 62 0II IIIMIII 1IIIMIIIIII
3 1262 09230 3964

















S t




g