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UNITED STATES DEPARTMENT OF AGRICULTURE - Ag -
BULLETIN No. 231. ey

Contribution from the Bureau of Entomology co
L. O. HOWARD, Chief

_ August 2, 1915.

Washington, D. C. , PROFESSIONAL PAPER

RECENT STUDIES OF THE MEXICAN |}
COTTON BOLL WEEVIL

B. R. COAD, Entomological Assistant, Southern Field
Crop Insect Investigations

4
CONTENTS le
F Page Page
bs Introduction . . 2. 2. 2 2 2 sw ee 1 | Development. ... . ; ai Beep eh aa,
if MUStrADUtlOM eh scl) as ice, shar Sed Gig 2) | Mibernation: 6 ei tyes eet ven heroes 31
Boad Plants 5 oo) Shoe 8 ee eee ae 3 | Natural Control . . . . 2. « © « « « 31 |
Characteristics of the Adults . .... 4 | Behavior of Louisiana Weevils at Victoria 32
Longevity of Adult Weevils . .... 6 | Development of Thurberia thespe-
SEE ACG) SA CL gn Nc AR 10 SIOTIRES AS 6 6k Sir ein eh Noah ueaeeee 33.
MEPFOUMCHON o iiciiig (oh er oy a) oe eles 10 | Examination of Thurberia bolls 33

WASHINGTON
GOVERNMENT PRINTING OFFICE
1915

UNITED STATES DEPARTMENT OF AGRICULTURE

BULLETIN No. 231

Contribution from the Bureau of Entomolegy
L. O. HOWARD, Chief

Washington, D. C. PROFESSIONAL PAPER August 2, 1915.

| RECENT STUDIES OF THE MEXICAN COTTON
| BOLL WEEVIL.

By b. Rh. Coan, Entomological Assistant, Southern Field Crop Insect Investigations.

CONTENTS. ;
Page. Page.
MAEHOGUCHION a ey seis. Sei 42 ge She Shy qe ets: ie eDevelopimentias soos. 02 UR ys See a ie 27
irs) TD AIS (EITN UA it Cosa eae ee eat a a a ea O)y lil BEN oYeyao RA AOF Ole oes Paasiehe see greet Bs eae sak 31
TROOC IMIG See Goee Hes ScieuioGeeinE a ere ie Se eNiatural(comtrole st. 22. sey ss eee eee eee 31
Characteristics of the adult.................- 4 | Behavior of Louisiana weevils at Victoria...- 32
Longevity of adult weevils.................. 6 | Development of Thurberia thespesioides....-. oo
SExtOMacduilits es ae we en MME ia ts. 10 | Examination of Thurberia bolls............-. 30
EVEDLOCUGHIOM 6 ace ct come ete eh ees to 10
INTRODUCTION.

The cotton season of 1913 was of great importance in the study
of the boll weevil, Anthon-
omus grandis Boh., because
of severalopportunediscoyv-
eries. Briefly, the events
of the year were the dis-
covery, by Mr. O. F. Cook,
of the cotton boil weevil
breeding upon a wild-
cotton plant, Thurberia
thespesioides, in Arizona;
the establishment of breed-
ing work at Victoria, Tex.,
for the purpose of study-
ing any changes in the life
history of the weevil; the
‘discovery by the writer of
important food adapta-

tions of the weevil; ex- 3 Ra
l ti al th t ' Fig. 1.—Distribution of the Mexican cotton boll weevil. The
_ piorations oF southeastern shading shows the infested area; the heavy Lines, the limits

Ar izona by Dr. ie W. Morrill of cotton production; the broken line, the probable distribu-
1 1 i i i il. (Original.
and Mr. W. D. Pierce in tion of the Arizona wild cotton weevil. (Original.)

August, by Mr. Vernon Bailey later in the fall, and by Messrs.

Notr.—This bulletin is of interest to entomologists in the cotton belt.
89032°—Bull. 231—15——1

2 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE,

KE. A. Schwarz and H. S. Barber in December, 1913. The results
of the explorations and research work are quite fully treated in the
body of this article.

Mr. Cook’s announcement, which was published in February, 1913,
was followed by departmental press notices issued in October of the
same year, and by a detailed article by Mr. W. D. Pierce describing
the Arizona weevil as a new variety, Anthonomus grandis var. thur-
berize, issued November 10, 1913.?

A paper by the author on the food habits of the boll weevil in
Texas has recently been published.

This bulletin deals with a number of rather technical experiments
and observations which have important bearings on the general boll-
weevil problem. The principal matters dealt with are, first, the exact
relation between the typical boll weevil, Anthonomus grandis Boh.,
and the form A. grandis thurberiz Pierce, which has recently been
found attacking a cottonlike plant in Arizona; and, second, the
changes in the habits of the boll weevil which have taken place since
it first entered the United States.

The importance of the first point mentioned lies in the fact that the
western form of the boll weevil has adapted itself to life under ex-
tremely arid conditions, i which respect it differs conspicuously from
the typical boll weevil. It therefore appears that the western weevil
might thrive in the drier portions of Texas, where the typical weevil
has not been able to establish itself, and thus reduce the production of
cotton in a large area which has been depended upon to offset the loss
caused by the boll weevil in more humid regions. Consequently,
exact knowledge regarding the life history and habits of the Arizona
weevil and its relation to the typical weevil are of importance.

The second matter dealt with in this bulletin, namely, the extent to
which the boll weevil has changed its habits since it has been in the
United States, is of great practical importance. More than 10 years
ago a careful study of the habits of the typical boll weevil was made at
Victoria, Tex. The present manuscript deals with similar studies just
completed at the same place. These studies give an exact basis for
estimating the extent of the departure from the original habits and
serve to bring greater accuracy into predictions as to the ultimate
nature of the boll-weevil problem in the United States.

DISTRIBUTION.

The discoveries of the year have added to the present knowledge of
the distribution of the species. On the accompanying map (fig. 1)

1Cook, O. F. A wild host-plant of the boll weevilin Arizona. Science, n.s., v. 27,no. 946, p. 259-261,
Feb. 14, 1913.

2 Pierce, W. D. The occurrence of a cotton boll weevilin Arizona. U.S. Dept. Agr., Jour. Agr. Research,
y. 1, no. 2, p. 89-96, Nov. 10, 1913.

’ Coad, B. R. Feeding habits of the boll-weevil on plants other than cotton. U.S. Dept. Agr., Jour,
Agr, Research, v, 2, no, 3, p. 239-245, June, 1914,

Sey slits Wetany dil laid sce) tis

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 3
it will be seen that there are three apparent lines of distribution of the
species, with Costa Rica as the apex. One line of distribution is along
the Pacific slope, and although, according to present knowledge, the
Arizona infestation is isolated from that of Sinaloa, Mexico, it is prob-
able that the weevil occurs on Thurberia thespesiordes in the moun-
tains between these poimts. The Thurberia plant is known from
Chihuahua and Guadalajara, Mexico, which latter locality 1s within a
few miles of weevil-infested cotton.

The dispersion following the middle line is historic. Simce 1880
this movement has been watched more or less thoroughly from
Tamaulipas, Nueva Leon, and Coahuila, Mexico, until now (1914)
it has reached the Georgia line (fig. 1).

The third line of distribution from Mexico through Yucatan to
central Cuba is the cause of considerable speculation as to whether
Cuba or the continent was the original source. There is also some
speculation as to whether the Central American infestation furnished
the nucleus for the dispersion or whether the weevil originated in
southern Mexico and dispersed southward. |

FOOD PLANTS.

The plant longest known as the food plant of the boll weevil is
cotton, of which several species are now recorded as hosts—Gossy-
pum hirsutum, G. herbaceum, G. barbadense, G. brasiliense, and also
several Mexican species.

Mr. Cook’s announcement added as a native food plant the so-
called Arizona wild cotton, Thurberia thespesiordes, which grows in a
number of mountain ranges in southeastern Arizona, and also in
parts of Mexico and probably New Mexico.

During the summer of 1913, following the discovery of a boll weevil
feeding on cultivated Hibiscus syriacus at Victoria, Tex., the writer
succeeded in rearing the species on buds of this nine fed them for
some time, and noted the partially complete development in buds
of Callirrhoé involucrata and C. pedata, and kept them alive on Sphe-
ralcea lindhevmerr buds for a short period.

In the above series of experiments, by alternating foods it was
found that the weevils have a wide range of hitherto unsuspected
adaptability. This discovery makes the presence of malvaceous
plants in the vicinity of cotton a possibly important factor in the
ultimate control of the species. The greatest importance of this fact
would arise in any attempted cessation of cotton planting as a control
measure against the species. |

CHOICE OF FOOD PLANT.

Two male and two female boll weevils reared from Thurberia buds
imported from Arizona were placed with Thurberia buds and with
cotton squares to test their food preference. They began feeding

4 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE,

_immediately on both foods, but usually fed slightly more on the cot-
ton squares than on the Thurberia buds. When egg deposition
started the greater number of the eggs were deposited in cotton
squares. These observations were continued for 15 days. ¢

From these experiments it would appear that, when in captivity,
weevils reared from Thurberia will feed on cotton squares just as
readily as they will on Thurberia buds. The slightly greater amount
of feeding on cotton squares in this experiment may or may not
have any significance, and it was probably purely accidental.

These secant medion in the laboratory are in strong contrast with
those made in the field. At Victoria the Thurberia plants under
cultivation were within 50 feet of a small patch of cotton. This
cotton was heavily infested by weevils throughout the season and
not a boll was able to reach maturity. On the other hand, although
the Thurberia plants were just as much exposed as the cotton, not a
single indication of weevil work was found on the plants im not a
weevil was found on them.

In Stone Cabin Canyon, Santa Rita aera Anz. MreWwobs
Pierce was unable to find a weevil on cotton plants growing within
10 feet of Thurberia plants which were heavily infested with weevils.
In December this same cotton was examined by Messrs. Schwarz
and Barber and they were unable to find a sign of weevil work in the
bolls.

Tn this connection records made on the habits of larve: of the cotton
leafworm (Alabama argillacea Hiibn.) are of interest. These larve are
almost exclusively cotton feeders, but in the laboratory tests they
fed on the Thurberia leaves as eed as on cotton when both were
offered and were able to pupate and reach maturity on this food.
In Stone Cabin Canyon this species was found feeding on Thurberia
plants. The species was common on cotton at Tinea and Phoenix,
Ariz. At Victoria, Tex., this species acted exactly as did the native
weevils, with relation to the cotton and Thurberia patches. The
cotton was heavily infested and only preserved from destruction by
spraying, but not a single leafworm larva was ever found on the
Thurberia plants. The moths were very numerous for a considerable
period and eggs were abundant on the cotton, whereas careful
examination failed to show an egg on the Thurberia plants.

CHARACTERISTICS OF THE ADULT.
DESCRIPTION OF THE SPECIES.

Owing to the recent studies on the variations of this species it
becomes necessary to reconstruct the descriptions given by Boheman

1 Experiments during 1914 in Arizona have proven that the Thurberia weevils will attack growing
cotton,

RECENT STUDIES OF’ THE MEXICAN COTTON BOLL WEEVIL. 5

and Dietz in order to include all variations. These descriptions are
the joint work of Mr. W. D. Pierce and the writer:

Anthonomus grandis Boheman. [Redescribed.|—Stout, subovate to ovate, ma-
hogany red to piceous and clothed with coarse baryta-yellow to raw sienna pubescence.
Beak long, slender, shining, and sparsely pubescent at the base; more or less dis-
tinctly striate to about the middle; apical half finely and remotely punctured; the
beak of the female is slightly longer and more slender than that of the male, more
shining, and less coarsely punctured and striate. The female antenne are inserted
at about two-fifths of the distance from the apex of the beak to the eyes, while the
male antenne are inserted at one-third the distance from the apex. Antenne slender;
second joint of funicle longer than the third; joints 3-7 equal in length, but becoming
gradually wider. The club may or may not be concolorous with the funicle and is
more or less distinctly annulate. Head conical, pubescent, coarsely but remotely
punctured, front foveate. Eyes moderately convex, posterior margin not free.
Prothorax about one-third wider than long; base feebly bisinuate, posterior angles
more or less rectangular; sides almost straight from base to middle, or slightly con-
verging, strongly rounded in front; apex sometimes constricted and transversely
impressed behind the anterior margin; surface moderately convex, densely and
sometimes subconfluently punctured; punctures irregular in size, sometimes coarser
about the sides; pubescence variable, often denser along the median line and on the
sides. Scutellum variable. Elytra oblong, scarcely wider at the base than the
prothorax; sides convex or subparallel for two-thirds of their length, thence gradually
narrowed to and separately rounded at apex, leaving the pygidium moderately
exposed; strise deep, punctures large and approximate; interstices convex, rugulose,
pubescence somewhat condensed in spots. Legs rather stout, femora clavate, anterior
always strongly bidentate, inner tooth long and strong, outer one variable in shape
but connected with former at base; middle and posterior femora unidentate or
bidentate. 'Tibise moderately stout, more or less bisinuate internally; tarsi moderate,
claws broad, blackish, and rather widely separated; tooth almost as long as claw.
Length ftom 2.3 to 6.75 mm.; width from 1.1 to 3.6 mm.

Anthonomus grandis Boheman. [Typical variety.]|—Stout, subovate, almost pice-
ous, and clothed with coarse, baryta-yellow pubescence. Beak long, slender, shining,
and sparsely pubescent at base; more or less distinctly striate to about the middle;
apical half finely and remotely punctured; the beak of the female is slightly longer
and more slender than that of the male, more shining, and less coarsely punctured and
striate; the female antenne are inserted at about three-fifths of the distance from the
apex of the beak to the eyes, while the male antenne are inserted at one-third of the
distance from the apex. Antennz slender, second joint of the funicle longer than the
third; joints 3-7 equal in length, but becoming gradually wider; concolorous through-
out, usually mahogany red; club rarely distinctly annulate and usually with only the
faintest traces of whitish hairs on the apical margins of the first two joints. Head
conical, pubescent, coarsely but remotely punctured, front foveate. Eyes moder-
ately convex, posterior margin not free. Prothorax about one-third wider than long,
base feebly bisinuate, posterior angles more or less rectangular; sides usually almost
straight from base to middle, or slightly converging, strongly rounded in front; apex
sometimes constricted and transversely impressed behind the anterior margin; surface
moderately convex, densely and sometimes confluently punctured; punctures irregu-
lar in size, sometimes coarser on the sides; pubescence condensed in a sharply defined
median vitta distinct from base to apex, also denser on sides. Scutellum narrow,
elongate, convex, usually cylindrical, rounded oblong. Elytra oblong, scarcely
wider at base than the prothorax; sides subparallel for two-thirds of their length, thence
gradually narrowed to and separately rounded at apex, leaving the pygidium moder-
ately exposed; strie deep, punctures large and approximate; interstices convex, rugu-

6 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE,

lose, pubescence somewhat condensed in spots. Legs rather stout, femora clavate,
anterior strongly bidentate, inner tooth long and strong, outer one variable but con-
nected with former at base; middle femora unidentate in male, rarely with minute
second tooth in female; posterior femora unidentate. 'Tibize moderately stout, more
or less bisinuate internally; tarsi moderate, claws broad, blackish, and rather widely
separated; tooth almost as long as claw. Length, from 2.3 to 6.75 mm.; width, from

1.1 to 3.6 mm.
Anthonomus grandis thurberiz Pierce.—Stout, ovate, mahogany red, and clothed with

coarse, raw slenna pubescence. Beak long, slender, shining, and sparsely pubescent.

at base; more or less distinctly striate to about the middle; apical half finely and
remotely punctured; the beak of the female is slightly longer and more slender than
that of the male, more shining and less coarsely punctured and striate; the female
antennee are inserted at about two-fifths of the distance from the apex of the beak to
the eyes, while the male antenne are inserted at one-third of the distance from the
apex. Antenne slender, second joint of funicle longer than the third; joints 3-7 equal
in length but becoming gradually wider; the club piceous black, scape and funicle
mahogany red; club with apical margins of the first two segments usually distinctly
annulate with fine whitish hairs. Head conical, pubescent, coarsely but remotely
punctured, front foveate. Eyes moderately convex, posterior margin not free. Pro-
thorax about one-third wider than long; base bisinuate, posterior angles more or less
rectangular; sides usually converging from near base to apical third and thence strongly
convexly narrowed to apex; apex sometimes constricted and transversely impressed
behind the apical margin; surface moderately convex, densely and sometimes sub-
confluently punctured, punctures irregular in size, sometimes coarser about the sides;
pubescence evenly distributed; without sharply defined vitte. Scutellum broad,
subquadrate, rarely subtriangular, flattened. Elytra broad, scarcely wider at the
base than the prothorax; sides slightly convex in basal two-thirds, thence strongly
convexly narrowed and separately rounded at apex, leaving the pygidium moderately
exposed; strie deep, punctures large and approximate; interstices convex, rugulose,
pubescence more regular but slightly condensed in spots. Legs rather stout, femora
clavate, anterior always strongly bidentate, inner tooth long and strong, outer one
variable in shape but connected with former at base; middle femora bidentate; poste-
rior femora almost always unidentate. 'Tibize moderately stout, anterior and median
_ bisinuate internally, posterior straight; tarsi moderate, claws broad, blackish, and
rather widely separated, tooth almost as long as claw. Length, from 2.5 to 6.7 mm.;
width, from 1.8 to 3.6 mm.

LONGEVITY OF ADULT WEEVILS.

Several series of experiments were conducted to determine the lon-
gevity of the weevils upon different foods. ‘These experiments not
only compare the two varieties of the weevil, but compare weevils
from Tallulah, La., with those from Victoria, Tex.; various Malvaceze
with one another and with a diet of water only; different parts of the
same plant; different seasons; and also the two sexes. The data
obtained are presented in concise form in Table I.

salah USE, Shes yo bast SB i ep

lA fea BE

hae 4
7

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 7

The maximum record of longevity made in the 1913 work is based
on a specimen of Anthonomus grandis thurberix, extracted from its
hibernation cell August 27, after at least nine months in hibernation,
which was still alive when the food supplies at Victoria gave out,
October 29. This gives the maximum known period of hibernation
as 270 days, and a total of over 333 days longevity. The maximum
recorded length of life is 335 days for a hibernated weevil at Tallulah,
La., in 1910.1

The maximum length of life of weevils after emergence from
hibernation was 73 days for males and 71 days for females, both of
which records are far below the highest previous records.

A true comparison of females fed on blooms of Hibiscus syriacus
gives the average longevity of Arizona A. g. thurberie as 22.5 days,
Texas A. grandis as 16 days, and Louisiana A. grandis as over 27
days.

The grandis males neotaged 3.47 days on water, 5 days on Spheral-
cea lindhevmeri, 7.6 days on Callirrhoé pedata, 17.5 days on Hibiscus
syrvacus, 20 fae on Callirrhoé involucrata, and 33.2 days on cotton,

while the thurberix males averaged 27.6 days on Hibiscus syriacus.

The grandis females averaged 3.32 days on water, 5.4 days on both
Sphexralcea lindhevmert and Callirrhoé pedata, 19.2 days on Hibiscus
syrvacus, and 34.3 days on cotton, while the thurberiz females averaged
25.5 days on Hibiscus syriacus.

The greater longevity of weevils on the same food later in the
season is very evident and is due to the advance of hibernation
temperatures.

Although the records of life on cotton were shorter than those
previously obtained when the totals are considered, it is noted that
they agree quite well for any given season. It is evident that tem-
perature and humidity exercise considerable control upon the length
of life on any given food. The average longevity on cotton leaves
was 11.9 days, on bolls 17.2 days, and on squares 42.1 days.

Adding these new records to those previously obtained 5,858
weevils fod on water only averaged 10.1 days; 16 weevils fed on cot-
ton leaves only averaged 11.9 days; 226 weevils fed on miscellaneous
malvaceous plants averaged 13.2 days; 92 weevils fed on cotton
bolls averaged 19.9 days; 4,353 weevils fed on cotton foliage aver-
aged 24.5 days; and 147 weevils fed on cotton squares averaged 59.5
dees. |

Comparing the sexes irrespective of food in all experiments hitherto
conducted 4,226 males averaged 17.7 days, and 3,624 females
averaged 18.5 days.

1 The longevity records of 1913 have been greatly exceeded during 1914 in experiments conducted at
Washington, D.C. Weevils have been kept in a dormant state for over a year, and give promise of living
considerably Ore

BULLETIN 231, U..S. DEPARTMENT OF AGRICULTURE,

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89032°—Bull. 231—15

10 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE.

It is important to note that the maximum longevity on water was
6 days, on Spheralcea lindhermert 15 days, on Callirrhoé vnvolucrata
20 days, on C. pedata 26 days, on Hibiscus syriacus 43+ days, and on

cotton 74 days.
SEX OF ADULTS.

The material studied during the year was all sexed and the records
have been tabulated to show the seasonal abundance and for com-
parison of the varieties (Table II).

TaBLE I].—Relative proportions of the sexes of boll weevils.

Male. | Female.
. Variety and description of material.
Number. | Percent. | Number. Nomber [Percent Per cent.
|
Grandis:
Eipermated weevilss caso sstces- Secu eee tase Soe eae ee ees 674 67. 88 at 32. 12
hirsfeeneration collectedit sees sete seceee eae eee eee ae 73 53. 3 46.7
Wollectedan Augusta aos ece cece oe a eee eee 158 62. 0 97 38. 0
PBECG 2a oe core sieve cic wise es Serieceaninssc so ee meee cumaaae eee 557 52. 6 500° 47.4
Motal andiaverape.s-.2--.-0 ee ee | 1,462 | . 59.8 980 40.2
Thurberiz: Bice 5S oe ee
Collected ini August 7 2- casee se See es ee eee ee | 21 51.3 20 48.7
Bred from Thurberia bolls in September.........-.--.----- | 11 50. 0 11 50. 0
IBTedtronucottominat ne tales se yee ee eee | 20 62.5 12 SYA SS
Extracted from Thurberia bolls, March, 1914 cee eee ee 71 en 52 42.3
Motaliand average: 221%. 1- oss eee eee 123} 56.9 | 95 43.1
Hybrids: | |
I NHUTIE DK. CRU pepe are one o> ap Sdemcesodeacn sence ee 22 59.4 15 40. 6
pecond generayiOn me a. . eee eee ee | 21 42.0 29 58.0
INGE POSIEIV.CICEOSSES 322 fos ase a a eee eee | 135 51.0 130 49.0
SiG Ndisx< Other Perigo eee se ae eee ee il 45.8 13 54. 2
Second: geoneration=— 2 22 sie aes cee oe ee ones | 15 | 57.7 11 42.3
ING EPOSICIV@CLOSSCS 252-6 cose eco reer see ere 20} 51.3 19 48.7
Potaland Average: sf oe eae ee ee | 224 | 50.7 217} 49.3
| SS SS
Total and average all weevils............-..-..------- | 1,809 | 58.3 | 1, 292 | 41.7

Separating this material into hibernated and spring or summer
bred weevils, there are in the hibernated material 777 males and 402
females, or 65.9 per cent males and 34.1 per cent females, while the
spring and summer bred weevils numbered 1,032 males and 890
females, or 53.6 per cent males and 46.4 per cent females. |

The total of all records to date gives 8,826 males and 6,710 females,
or 56.7 per cent males and 43.3 per cent females.

It is noticeable that there is a larger percentage of females in the
variety thurberie and in the hybrids than in the variety grandis.

REPRODUCTION.

RELATION OF FOOD TO COPULATION.

To test the period from emergence to copulation, a number of lots
of males and females of the variety A. grandis were separated by
sexes immediately after emergence and placed on either cotton

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 11

squares, leaves, or bolls. In each lot the weevils were paired off
together for a few hours daily while under close observation. As
soon as a pair copulated they were removed from the lot and the
remainder tested until they either copulated or died. In this copu-
lation series 23 pairs of weevils fed on squares, 2 pairs fed on bolls, and
1 pair fed on leaves copulated. These figures are of more value when
taken in relation to the number of pairs of weevils that refused to
copulate before death on the different foods. This relation 1s shown
in Table ITI.

TaBLE III.—Relative proportion of boll weevils copulating on different foods.

Number pairs
of weevils Number

: Percentage
Food. carried to airs
either copula- conuiaeed? copulated.
tion or death.
Per cent.
COGUOTYS TATE Stays yey ee a es III a eet Bie geal Se Si aaa 38 60
CotLtOMMDOL ISH Saree patty sae she ane any Aya ep eel tcycaeelas 8 2 25
WOtGEOTMe A WeSE ere yess ree sen no ares iten Corio: Butane it ate lie Ne naa) ne hi AEN 8 1 12

From this table it is seen that copulation is unusual when the
weevils are fed strictly on either cotton bolls or leaves.

AGE AT WHICH FERTILIZATION TAKES PLACE.

The length of the period before copulation depends in a large
measure upon the temperature as well as upon the food. For square-
fed weevils this period varied from 3 to 10 days, with a weighted
average of 5.8 days.

In the series of boll-fed weevils only two records were made on
this period. Both of these were in the latter part of June and were
6 and 8 days, respectively, giving an average of 7 days.

In the leaf-fed series only 1 pair copulated, and they gave a period
of 5 days. , ;

The records on boll-fed and leaf-fed weevils are too few in number
to offer any comparison with the length of the period for square-fed
weevils and serve only to emphasize the difficulty with which the
hfe functions are performed on these unnatural foods.

The period from emergence to copulation was not determined
exactly for the weevils fed only on buds and blooms of Mibiscus
syriacus, but some idea of the period can be secured from the first
date the weevils were observed in copula while making the daily
examination. Two pairs of A. g. thurberize were first observed in
copula in 6 and 14 days after emergence, while at the same time
(September) two pairs of A. grandis were first observed in copula
in 9 and 13 days after emergence. These records and the frequency
with which the weevils were observed in copula later show that the
proper element to stimulate copulation is present in the food.

12 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE.
PERIOD FROM FERTILIZATION TO OVIPOSITION.

The period from fertilization to oviposition was secured as a
continuation of the experiments described under the period from
emergence to copulation. After the females in this series copu-
lated once they were placed on food and watched for the first egg
deposited. In this manner the period was determined. In most
cases the male was removed after the first fertilization, but in a
few cases the male was placed with the female for a short period
each day and the copulation noted. In this way as many as five
copulations were noted for a female before a single egg was deposited.
The periods determined are noted according to the food.

Weevils fed on cotton squares.—During June, July, and August this
period was observed for 21 females fed only on squares. The period
ranged from 1 to 7 days, with an average of 3.9 days.

Weevils fed on cotton bolls —Three pairs of boll-fed weevils were
observed from first copulation to oviposition. The period for these
weevils ranged from 3 to 7 days, with an average of 5 days.

Weevils fed on cotton leaves.—Only one pair of weevils started copu-
lating when fed only on cotton leaves from emergence. This female
emerged July 7 and copulated the first time on July 11. She lived
until July 24 and copulated 8 times in the interval. No eggs were laid.

PERIOD FROM EMERGENCE TO OVIPOSITION.

In the series of typical grandis the period from emergence to ovipo-
sition when on squares constantly varied from 3 days to 13 days,
with an average of 6.1 days for the positive records.

With typical thurberiz the three cases recorded ranged from 3 to 6
days, with an average of 4 days. These records are too few in num-
ber to allow a positive comparison with those for grandis, but the
average is just about the same as for the latter during the same
period (early September).

Two pairs of progeny of female grandis by male thurberiz began
to oviposit in 4 and 7 days each or an average of 5.5 days.

Two pairs of progeny of female thurberiz by male grandis began
to oviposit in 5 days each. ;

The period from emergence to oviposition was observed with six
pairs of grandis fed only on buds and blooms of Hibiscus syriacus
from maturity. Three of these pairs observed durmg early June
varied from 5 to 6 days, and averaged 5.6 days. The other three
pairs, observed during September, ranged from 11 to 18 days, with
an average of 13.6 days.

This period was also observed with two pairs of thurberie on the
same food. These began to oviposit in 12 and 16 days, or in an
average of 14 days.

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 13
PERIOD FROM FIRST FEEDING ON SQUARES TO OVIPOSITION.

The period from first feeding on squares to oviposition is shown
for hibernated A. grandis females in Table IV.

TasLeE 1V.—Time from first feeding on squares to.oviposition for hibernated females of
A. grandis.}

Total pe-
Period fed | riod from

Collected First fed | First eggs on squares | first fed

“~? | on squares, | deposited, to deposi- | on leaves

Mayr May— tion. to deposi-

tion.
Days. Days
Sees 14 22 8 14
Shesoasee 14 19 5 11
Sees 15 20 5 12
See 17 19 2 11
LO se wheat 24 25 1 15

AVES Nears 30 eiseareys| werent e Becles 4.2 12.6
INN Ratpree sl Beet er tease keh aa akg The 8 tS
MTN ese eee nes Masel eas ie sed sl 1 11

1 These weevils were collected in the field before squares began to form and fed pon leaves until the
dates noted above.
_ The weevils were collected in the field before any squares were
formed and were fed only on cotton leaves until the dates given for
placing on squares. It is seen that the period ranged from 1 to 8
days with an average of 4.2 days. An interesting point, however, is
the fact that the time from the change from leaves to squares as food
to the beginning of oviposition seems to vary inversely with the time
fed on leaves. The totals of these two periods or, in other words,
approximately the time from first feeding on the cotton plant to ovi-
position, are surprisingly similar. They vary from 11 to 15 days with
an average of 12.6 days.

This period for female thurberxx paired with male grandis was 12
and 15 days in the two cases tested in May and June. This gives an
average of 13.5 days. In early September this period ranged from

2 to 5 days with an average of 3 days.

During the early part of S saticaltier this period for typical thurberix
varied from 1 to 3 days with an average of 2.2 days.

In all these series where female thurberiz were used the individuals
were extracted from their hibernation cells in Thurberia bolls and
placed on cotton squares immediately.

The period from first feeding to oviposition of early hibernated
females was observed in only one pair of weevils fed on the buds and
blooms of Callirrhoé pedata. This female began depositing eggs 6
days after being placed on this food. As these weevils were collected

during the early part of May they had probably fed very little, if at
all, on cotton.

14 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE.
DURATION OF FERTILITY AND FECUNDITY.

Many experiments were conducted to test the duration of fertility
and the fecundity of the various types of weevils. With A. grandis
special experiments on this question were conducted in addition to
the regular breeding series. Rather thorough data were obtained on
the variety thurberiz and the various crosses in the different breeding
series of these. 3

Fecundity of females of A. grandis in copula only once.—The previous
results on the exact duration of the fertility of females after copula-
tion were very indefinite and there were no records of the fecundity
resulting from only one copulation. In the course of the past sum-
mer’s investigations the writer was able to secure considerable infor-
mation on this point. |

Eleven females were separated from the males immediately after
emergence and only returned to them about 6 hours each day when
under close observation. In this manner the first copulation of each
female was determined and she was then placed alone on squares to
test her fecundity with no more chances for fertilization. Of the
11 females so treated, five were fertile, four were infertile but deposited
eggs, and two failed to deposit any eggs. Of the two that did not
deposit eggs, one was In copula 25 minutes and the other 10 minutes.
Each of these lived a short time and then died. The fecundity tests
of the remainder gave the results found tabulated in Tables V and VI.

TasLte V.—Fecundity of females of A. grandis in copula only one time and rendered
Jertile in that time.

{ i =

Oviposition. Eggs deposited. | Eggs per day.
Duration of fertility. | (Opes | Bees 3 ue |
Fees itl : : xter-| Nor- | Aver- | Maxi-
Started. | Ended. | Period. nally. | mally.| age. | mum.
Minutes. Days. i
To end of oviposition. - 24 | June 28} Aug. 7 41 348 | 0 348 8.5 rahe
owas. 102-2 --------- 145 |}...do....|] Aug. 27 61 456 9 447 7.4 21
To end of oviposition. . 26 | June 30 | July 18 19 87 0 87 4.6 7
WO ee sees Sess 231 | July 12} Aug. 12 32 | 237 0 237 7.4 17
IDs ae eee eel 29 | Aug. 9] Sept. 4 7 32 0 32 1.2 3
Motalee oes 2-252 155i | 25 Se. See ees 180 | 1,160 9:| (Al IBY eee eee ee
MVOrAR eS tera ce2 cece Ws < 315)| 30 eects | = Neg acre 36 B35 [ok ob a| oe a
Weighted average. -... Beet ay bees ag {-sthcacee feeeee ec eee ees Seat pee a7 6/4 wea:
MAAS 2 2 S55 os - BD see et [Scene 61 456 9 447 8.5 21
Mininiur: <= 25: .5.12.: DEES COMA LES | eee 19 | 32 | 0 32 12 3
I

1 Copulated twice (22 and B minutes respectively) with interval of 12.5 minutes between copulations.

2 Copulated four times (7, 4, 2, and 18 miautes respectively) between 10:04a.m.and11:18a.m. Remain-
der of the weevils were in copula only onetime. These copulations were with so very little time between
them that they were considered as one fertilization.

RECENT STUDIES OF’ THE MEXICAN COTTON BOLL WEEVIL. 15

TaBLE VI.—Fecundity of females of A. grandis in copula only one time and not fertilized.

Total, average
ete.

Min. Days. Days.
Beeston soot sis 3 June 29} June 29 1 1 0 1 1 1 4
Mea UAT Scare iia 7.5 | June 30 | Aug. 26 58 67 51 16 1.1 6 1
Be ei ca ct at a2 19 July ws duly, ot 1 3 0 3 3 3 8
Meet tse acini ners Sid jae Om asa|) sulye 3 3 3 0 1 1 35
Total CROs ers eS es ce 63 51 7S ee Saree GEDA 48
Average....... RAS uli akan ces ESI ahs Belle WSU e crises ie tate OD | RTC 12
Weighted av-
CLA eee ats eye cee ease orl ings mieapes ayo eran et eR eS Meu Ss oR Se yoke 1 EES ess pa eh al
Maximum. BON Gene sone peru ane 58 67 51 16 3 6 35
NEMA salt Se) We loaoseseene [ean Sarasa 1 1 0 1 1 1 1

From Table V it is seen that the greatest fertility was with the

longest period of copulation (45 minutes). Beyond this there seems
to be very little relation between the time in copula and the resulting
degree of fertility. In the infertile females it is seen that periods of
25 and 37.5 minutes in copula still failed to result in fertility.
_ The total eggs deposited by the fertile females ranged from 32 to
456 with an average of 235 each for the five females. This average
is quite high, even in comparison with females having males present
throughout life. The infertile females deposited from 1 to 67 eggs,
with only one depositing more than 3 eggs.

The period of fertility of the fertile females ranged from 19 to 44
days with an average of 32.6 days. The average eggs per day ranged
from 1.2 to 8.5 with a weighted average of 6.4. This is a rather high
average when compared with the results secured in other deposition
series .

A comparison of these results seems to indicate that the time in
copula has very little influence on the resulting fertility of the female.
One female was not rendered fertile during 37.5 minutes of copulation
while four others were fertilized in less than this time. The shortest
time in copula which resulted in fertility of the female was 24 minutes,
but the writer thinks that this is not significant.

The high average of the eggs deposited by the females fertilized
only once would seem to indicate that one fertilization is sufficient
to produce the maximum fecundity of the female. While this may
be true in certain rare instances, the writer believes that such cases
will be very rare. In a different breeding series a few females were
allowed to deposit eggs from one fertilization until they stopped
deposition, then males were added and in every case the females
began depositing again and continued for some time. The female
with the highest deposition record in the one fertilization series
discussed above quite evidently reached the limit of her fertility 17
days before death and she deposited 9 infertile eggs in this period.

16 BULLETIN 231, U. 8S. DEPARTMENT OF AGRICULTURE.

From this evidence it seems clear that one copulation will often result
in fertilization, but will not usually suffice for complete fecundity of
the female.

Fecundity of females of A. grandis with complete record on copula-
tion.—Since very little was known concerning the exact number of
times a single female will copulate in the course of her life an attempt
was made to secure some information on this point.

Nine females were separated from the males immediately after
emergence and each was fed separately throughout life. A male was
allotted to each female and each day the different pairs were placed
together in dry glass tubes for a short time while under close observa-
tion and given a chance to copulate. The period spent in copula was
noted each time and in this manner a complete record of the copula-
tions of each female was secured. During the remainder of the day
the females were kept on fresh squares and the daily egg deposition
noted. The results secured in this series are shown in Table VII.

TaBLe VII.—Fecundity of females of A. grandis with com plete record of time in copula.

f | | i
| ipositi Aver- Max-
| I eee Oviposition. fe Eggs fas SEE
AMSTETCSSS [DNS | SEE | | TL ,- | 2um- num-
Total, average,etc. |incop- timein} time a a ber | ber
| via. jcopula.| per | Started. | Ended. | Period.) ©88°- Jexter-| °S85 | 88S
opula. nally,| Pet | per
| | Y-| day. | day.

Min. | Min. Days. | |
Be eae sR es ae 22-1490: 5 P5223) July. 2) Julys 29-1 28 204 O:|"zSaltands
Seas eee 30° || 667.5) 22:2) July 4) Aug. 9 |" 37 217 0} 5.8 18
ef Saree OSG een geting | 33 | 786057938 |. Gomes |GAtie DAG a 52 302 A/°5.8 15
cE ae eG 27 689.0] 25.5] July 5| Aug. 4] 31 112 0| 3.6 10
BF Pio sa le ees ee 29 | 650.5| 22.4] July 6| Ang. 12| 38 126 2| 3.3 10
EN Sain es 2 een 24 |- 563.0 23.4.) uly Ww lyAde.. Gly col 126 1| 4.0 10
Roper ted fee: | 18 | 369.0] 20.5|...do.....| Aug. 7| 32 |--208 0} 65| 14
Reon oncns Seon ces | 13 | 291.5 | 22.4) Joly, 9| Aug: 5|. 28 |." 65 0} 2.3 10
EiGeetr top yet st ok | 9 | 196.0] 21.7] July 11| Aug. 27| 17 | 32 0| 1.9 5
Potal Sees [OR 0 1470S atte csce | cee nce cal | Utena 294 11,392 vale bese
Awerape {250 Sle 2 23 Ls 22-7 | 52266: Wax OD e Queer eee ok el he oa 39.7) (- S154. 712. ees petsee
Weighted average _...- eae pase eae: [ek PS ee ae EAs” ae ee | eee ACT ee
Ma MUTO ea 33 786: 5 ia 2bs bal otc ce eee eran ae ee 2 | eae | ae ce 18
MINATAUIN Bae Sa oe 9 196. 0 2-5: | artes vas eee 7A Sey 0|] 1.9 5

The number of times a single female will copulate was found to be
much higher than was anticipated. With these 9 females the num-
ber varied from 9 to 33, with 6 females copulating more than 20
times. The average per female was nearly 23 times.

In spite of the great number of copulations the number of eggs
deposited by these females was not high in comparison with other
series. It may be that the fact that the females were of necessity
removed from their food for from 1 to 2 hours daily while with the
males had some effect on the egg deposition. The total number of
eggs per female varied from 32 to 302, with an average of 154.7 eggs
per female. This average is considerably lower than that for the
females fertilized only once The average number of eggs per female
per day was 4.7, which is also lower than the average for the once
fertilized females.

*
pe Ra gtiaigls

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 17

When the male and female weevils were placed together in the dry
tubes daily they very rarely failed to copulate. They would usually
unite within a few minutes after being being placed in the tube and
it was very rarely that they copulated at all if they did not start
almost immediately after having the opportunity. It was extremely
rare for the two sexes to remain together without copulation for a half
hour and then unite.

The various breeding series in which one pair of weevils were
together on squares were examined only once daily and many pairs
were found in copula day after day when making these daily exam-
inations. In the field it was very noticeable that a pair usually
united as soon as they were placed together on a plant. When wee-
vils are collected in the field and placed in a tube it is the com-
mon occurrence for many pairs to unite as soon as dropped in the
tube. Hence it seems probable that it is normal for a single female
to be in copula many times and for the weevils to copulate almost
whenever they meet in the course of their travels over the plants.

Three females deposited a total of 7 eggs externally. These eggs
were deposited during the days when the same females deposited
- other eggs normally. As the females were certainly fertile, owing to
the almost daily copulations, this shows that external deposition
of eggs may be due to some cause other than infertility. The eggs
deposited externally by these females were tested for viability and
all hatched.

Fecundity of A. grandis females after hibernating.—Twelve females
were collected in the field at Victoria, Tex., May 8 to 10, shortly after
emergence from hibernation, and fed on cotton leaves until squares
became available. Then each was placed with a male and given
fresh squares daily for oviposition. These females were all observed
until their normal death. The results secured are shown in Table

VIII:
TasLe VIII.—fecundity of females of A. grandis after hibernating.

Approxi- oe Gord
Average | mate ovi- ggs per day.

Number of females. peter ees eggs per position
elope Ge 1D ae Average. |Maximum.
Days.

PIE Es SEIS 8 LL) iene AUS ee AIRED aes 144 72 1 6. 0 14
ea a8 STO STUY apn RRR CTR a ea 673 336. 5 32 10. 5 1 20
ee ae BURNT nh Eas Me Ri face fe esos cy ta aio rare 302 302 3 5.7 12
een cera Pe ai tas al ek ph ctr ct ee woe teeA eo be 336 168 25 6.7 11
DRE nye am pn Siac Ay at LS Se UUs elie Aik 715 357. 5 55 6.5 12
Baie Site SER CU Eats a Sat BS a co en ERNIE ras Cae aM 701 350. 5 46 7.6 19
1SE.5 BORN WES EMER DOOR ESATO On Leer nIsae nape 100 100 13 7.6 ll
MIDGET) ON 1 Ue a eer sees a ENE a OAV Wake Ve ee AG i Aua |e chet ier oa oeecarseiee oats

PAN OLAS Oya te hee cre treehe soape reas nN Rite RP LBA RNAS Nate: 247.6 BOuS a Wace ieee tae | pee ee eas
MWelpihnitedbay erarenias canes cepacia ce slice) Penner Ne riMe lean were eae obs on. (bk ee orere ts
ANA posal an Ua TT repre teat oy ct ae ine meni eal SATAN Coch RR EAN 0971/38 358 55 10.5 20
MiiraaTrarT yeep te yeesane Aea a rae ty tele lens Neo Maia 72 12 il

1 The 2 females in this lot deposited 39 eggs in 1 day. Therefore one of them laid at least 20 eggs.
89032°—Bull. 231—15 3

18 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE.

Unfortunately 10 of these females were placed 2 to a breeding
cage, and consequently the records for each of these cages give the
activities of 2 females instead of 1. Therefore complete individual
records of these females can not be given.

The total number of eggs deposited by these weevils is very high.
The average per female in the different lots ranged from 72 to 358
eggs. The average for the 12 females is 247.6 eggs. ‘These averages
are considerably higher than those of the reared weevils of the later
generations. It was previously supposed that, owing to the vitality
used in passing the winter, hibernated females would deposit less eggs
than weevils emerged during the summer, but this is shown not to
be the case.

The previously recorded maximum number of eggs deposited by a
single female was 304. It is of considerable interest to note that 6
out of these 12 hibernated females evidently exceeded that number.
The average number of eggs per day ranged from 5.7 to 10.5, with
an average of 7.3. This also is greater than the average of any of
the later generations.

Fecundity of summer-reared weevils —Although the greater part of
the females used in the various generation series of A. grandis during
the season were not allowed to complete oviposition, 7 of them were
continued to completion. The activities of these females are shown
in Table EX.

TABLE 1X .—Fecundity of females of A. grandis in various breeding series throughout the

Considering the fact that these females were with males constantly,
were given fresh squares daily and were less disturbed than any oth-
ers, it is surprismg that their oviposition was so low. The maxi-
mum did not equal the average of the once copulated weevils and the
average is nearly 100 less than the average for the hibernated females.

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 19

The average number of eggs per day ranged from 1 to 8.2, with an
average of 3.3 eggs. This is also much less than the average for
either the hibernated or once copulated weevils. The maximum
number of eggs per day ranged from 5 to 14. In fact these weevils
showed a surprisingly low degree of fertility in all points.

Fecundity of females of A. grandis in experiments not continued to
completion.—Many of the females in the various grandis generation
series were allowed to oviposit only a short time and then stopped
because of lack of squares. Some interesting data were secured
from some of these weevils, as is shown in Table X.

Taste X.— Fecundity of females of A. grandis in experiments not continued to

completion.
i Eggs per day.
Experi- aie a
Oviposition started. ment Ou ipest foe

closed in egss. :

: Average. | Maximum.
Days

PATON Gene eee Bee eee Ree ate Cae Ske June 20 20 5.0 7
AMON) 2s rep er cease att acy iB tc Gl Up July 2 16 147 9.2 15
LCOS Se eerie ee Nara E ERS nybea Mm gee Sr meen NLA ML July 11 25 318 12.7 26
ARO) SG Ses pais tee cae Ioana RE aE lee July 12 6 45 eo 11
BBO) shes ate a ta ERC LN Ses ee RES OOS Gorge 6 99 16.5 21
PL BUG) es a Caan are SS Ee USE ae Onset 4 31 led fil
SOUS Ws ena boodvecsoas paumdcssaenconEoceuadéuense Sept. 21 14 53 3.7 8
SOD GH Oar Melee sienecnemransra np unaine Mavens oe an ECON A 13 73 5.6 10
SNe cb aT a as a a teem UPS S| Le Set eS me real een 16.5 26
iS Ga oo RO oa oP a A eget oe args ya Ne A aioe eects og On RA 3.7 7

This information is of principal value in giving maximum and
minimum records. One female in this lot gave the season’s maxi-
mum record for eggs deposited in one day. This was 26 eggs. Inci-
dentally this is the highest number of eggs deposited by a single female
in one day on record. This female was allowed to continue deposi-

_ tion only 25 days, but in this time she deposited a total of 318 eggs,

or an average of 12.7 per day.

Fecundity of typical A. g. thurberre fed on cotton squares.—Three
pairs of pure thurberie were mated on cotton squares in June, but
for some reason only one female deposited any eggs. This one
deposited 7 eggs with a maximum of 4 in 1 day and an average of
0.3 per day. These eggs were probably all fertile, as most of them,
at least, hatched. It is very hard to account for the fact that two
of these females laid no eggs and the other deposited so few. The
females of thurberre placed with grandis males at this same time
deposited a normal number of eggs.

The fall series of pure thurberie mated on cotton squares gave
much better results, as is shown in Table XI.

20 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE.

TABLE XI.—Fecundiiy of typical A. g. thurberiz.

|
Oviposition. | | Eggs per day. | Mean
Total )———————————_ te

Number of females. : ones res ee

Started | Ended. | Period. Average. | aaa period.

Days | 2 F

Yh a SRS at A ap wale as eee Sept. 7 | Sept. 7 | 1 at 1.0 Ps eee
Peers fare 2 ate OS eee es Sept. 3} Cct. 6 | 34 173 5.1 17 77.6
Hee eye aR oe er Sept. 2} Oct. -1 | 30 73 2.4 | 11 77.3
Se ee ee ea See eS doses. Oct. 2 31 90 3.0 8 71.4
j Ree Sa aye a alee AR ne ee ee ee Sept. 4] Oct. 6 33 76 2.3 | 8 | 77.4
Oban Soe Ss a SE eee 128 | Af 2" Sees os Se eee
PAWV GER EO os Se eS See ee |e eee ee 32 | UE Beene eee te ee Bescteece-
Wielehtediayerace. = 252s 2 seat ae en eee es fe ee BSE ae See iae oo Bee 77.4
Mspatsitei itso co Ss s~ oon Se eee eee 34 | 173 | 5.1 17 | ee
MIRTH: 225 aes oo en gi esa eee een 30 73 | 2.3 8. 2eee

1 Owing to the fact that this female deposited only one egg, the record is not included in the averages
and summary given.

Five pairs were mated, and while four females deposited fairly
well, the other deposited only one egg and is not considered in the
following discussion. The total number of eggs deposited by these
females ranged from 73 to 173, with an average of 103. The average
per day ranged from 2.3 to 5.1, with an average of 3.2, and the max-
imum in one day was 17. All of these records are very low in com-
parison with the results of practically all other series. On the
other hand, the thurberiz females mated with grandis males at this
time gave better deposition records.

Results of the mating of male of A. g. thurberiz and female of A.
grandis—!n June two hibernated grandis females collected in the
field were placed with male thurberie on cotton squares. ‘As these
females were undoubtedly fertilized by grandis males before being
isolated, this series did not result in positive proof of cross breeding,
but, as the weevils copulated freely, the later progeny were quite
probably hybrids.

These two females deposited 192 and 387 eggs, respectively, with
an average of 7.1 and 7.9 each per day. The average total number
of eggs per female was 289.5 and the daily average was 7.6. The
maximum number of eggs per day was 16 for each female. On the
whole this fecundity is quite high and the females were surely refer-
tilized by the new type of males.

In September three known infertile females of grandis were mated
with male thurberie on cotton squares immediately after emergence.
This resulted in the positive crossing of the two. The results of
_ these matings are shown in Table XII.

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 21

TasLe XIT.—Fecundity of positive crosses of male of thurberiz and female of grandis.

Oviposition. Eggs per day. Rags
NG er See ee Total tem pera-
Total, average, etc. of eggs. : Fanckton
females. | started. | Ended. | Period. Average. mere period.
Days. °F.
1| Sept. 7] Oct. 24 48 115 2.4 7 74.4
1| Sept. 4] Sept. 11 38 43 ngil 4 77.8
1| Sept. 5 | Sept. 17 13 69 5.3 8 78.9
Rotals seee se! s- SEU a an rane cen 2 99 PPS il Wi Ase ia Many eese a ae ged bm Ee
SAGV ETA Cte ese edie aioe heal ea Carb alere ait ees 33 TOS Ge oe ooo hcg a eo era
Wicizhitediaverageten cos cetya| cease seo [eee a3 seinn| es taeioe etl Beis saibeeiae Dee oer ee ices 76.3
IWIGh-aiiqipbaaye ee Fane ees Me meee (seis aaa a Bebe e os mae 48 115 5.3 £3) eR er
META es ee Re ees RR Ree eRe ne 13 43 1.1 Aol yh Oe ah

The total oviposition of these females was surprisingly low, ranging
from 43 to 115 and averaging 75.6 eggs per female. The average
number of eggs per day was only 2.3 and the maximum number of
egos in one day was only 8.

Results of the mating of male of A. grandis and female of A. g.
thurberie.—In June two of the female thurberixz received were mated
on cotton squares with male grandis collected in the field. As

these females had been shipped with thurberre males, there was a

possibility of their being fertile at the time of placing with grandis
males, but refertilization probably occurred.

These females deposited 115 and 130 eggs respectively, with an
average of 122.5 each. The average per day was 3.4 and 3.9 eggs,
making an average of 3.6 each for the two females. The maximum
in one day was 7 eggs.

In the fall three females of thurberiz reared from Thurberia bolls
received from Arizona were mated with the males of grandis on
cotton squares immediately after emergence. Thus positive crosses

were secured. The activities of these females are shown in Table

xerie

TaBLeE XIITI.—Fecundity of positive crosses of female of thurberix by male of grandis.

Oviposition. Eggs per day.

Number Total t Mean
Total, average, ete. of ote LN DEED
females. . CEES. Maxi. | ture for

Started. | Ended. | Period. Average. fein period

Days. Sie

1] Sept. 6} Oct. 27 2 95 1.8 8 73.9
1] Sept. 3] Oct. 2 30 146 4.8 13 fo8
Lea loe Oct. 8 36 102 3.0 8 80. 2
Total. sos accec Siilleeeee aie oe ere to 118 BY Bie IN Ae ere ee ue me ec opera te Toit
DAV CLAS Ce eineiepats estos Bed re rs atene | isis sere ates comes oe 39.3 Tie Tal (Paecaer a am ebe a e P Se
Wieiglitedtaverace meres |ecpics eee ee loops rs Bye ee ee ere no asl eM RN BI = De Que eeiee nme ae 76.7
Mi KATRIN pete eee os erate ee eI tee ere rea el Le 52 146 4.8 USS Seren veel
MGRINETEL USER eee fe eine oe | crcl ae ict ey ooh 30 95 8 Sri oso Saco

yo BULLETIN 231, U. $8. DEPARTMENT OF AGRICULTURE.

Here again the total eggs deposited was quite low and the average
eggs per day was likewise low. However the fecundity was quite
high enough to equal many of the grandis females depositing at the
same time; consequently there seems little reason to believe that .
the fecundity of thurberie is less than that of grandis.

Results of the mating of progeny of male of thurberie and female
of grandis.—In the latter part of June three pairs of weevils reared
from eggs deposited by doubtful crosses of male thurberiz and female
grandis were mated on cotton squares. Two pairs were placed
together in one jar and allowed to continue deposition until the
normal cessation. These two females deposited a total of 100 eggs
and averaged 4.3 per day. The maximum number in one day was
14 eggs. The other female was allowed to continue oviposition for
18 days, and in this time she deposited a total of 143 eggs at the
rate of 8 eggs per day. The maximum number for one day was
15 eggs. :

Results of the mating of progeny of male of grandis and female of
thurberie.—In July two pairs of weevils reared from eggs deposited
by doubtful crosses of male grandis and female thurberrx were mated
on cotton squares. Owing to the shortage of squares these weevils
were stopped after having deposited for 17 and 5 days, respectively.
The first female deposited a total of 131 eggs at the rate of 7.3 per
day, with a daily maximum of 15, and the second deposited 48 eggs
at the rate of 9.6 per day, with a daily maximum of 14.

MAXIMUM NUMBER OF EGGS PER DAY.

The maximum number of eggs deposited in 1 day by any female
was 26. A first generation grandis female emerging June 8 deposited
this number of eggs in cotton squares July 2. The mean temperature |
was 81.1° F. and the mean humidity was 68 per cent for the oviposi-
tion day involved. The previous record for 1 day’s deposition (20
eggs) was exceeded many times by quite a number of females.

The maximum number of eggs deposited by typical thurberiz on
cotton squares was 17. This number was deposited September 8 at
a mean temperature of 86.4° and a mean humidity of 78 per cent for
the oviposition day.

The maximum for the mating of infertile female thurberie and
male grandis was 13 eggs. This number was deposited September 10
at a mean temperature of 81.4° and a mean humidity of 83.5 per cent
for the oviposition day.

The maximum for the mating of infertile female grandis and male
thurberiz was 8 eggs. This number was deposited September 16 at a
mean temperature of 76° and a mean humidity of 77.5 per cent for
the oviposition day.

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 23

The maximum number for females fed only on buds and blooms of
Callirrhoé involucrata was 3 eggs.

The maximum for females fed only on the buds and blooms of
Hibiscus syriacus was 8 eggs.

RATE OF OVIPOSITION.

The daily rate of oviposition has already been shown in the discus-
sion of the general fecundity of the weevils, but the rate by fractions
of the oviposition period of the different females is also of interest.
In the following studies the oviposition period of each female has
been divided into thirds and the results tabulated accordingly. This
is shown in Table XIV.

TasBLE XIV.—Rate of oviposition of the boll weevil obtained in all experiments.

Rate of oviposition.

Number First third of | Middle third of | Last third of
Nature of weevils. | oe Season. period. period. period.
emales.

Hibernated grandis
females.

Once fertilized 5
grandis females.

Grandis females 9 | July to August........ 492 5.2 590 6.0 310 3.0
with a complete
record on copula-
tion.

Various breeding 6 | June to September.... 415 4.7 386 4.3 219
series of grandis.

Pure thurberiz....-- 4 | September, to October. 234 5.5 130 oul 46

Positive crosses of SEs Got eames ine 77 2.4 83 2.5 67
male thurberiz i
pod female gran-
is.

Doubtful crosses of 2 | May.to July......-...-. 142 5.6 283 9.5 189 ae,
male thurberixz
and female gran-
dis.

-Positive crosses of 3 | September to October. 155 4.0 127 3.2 61 1.5
male grandis and
female thurberiz.

Doubtful crosses of 2 | June to July.....--..- 81 3.9 101 4.4 63 Dai,
male grandis and
female thurberiz.

May to July.......-..-. 136 6.5 161 7.3 105 4.6

June to September... 521 9.0 484 8.2 155 2:

Wi
°

Here it is seen that the maximum rate of oviposition in the average
of all series is reached in the middle period and the minimum is in
the last period. However, there are several exceptions to this in the
averages of the different types of females. It is interesting to com-
pare the results of the spring and fall series. In the former the aver-
age of the middle third is much higher than the first and the last is
only slightly lower, while in the fall series there is generally a great
decrease in the latter part of the period. This differenze is of course
due to the temperature increasing from ae to summer and
decreasing 1 in the fall.

24 BULLETIN 231, U. $8. DEPARTMENT OF AGRICULTURE.
IS THE FECUNDITY OF THE WEEVIL DECREASING?

In previous bulletins on the boll weevil this question was put, but
not answered because of insufficient data. A comparison of the total
number of eggs laid by weevils at Victoria and the rate per day for
1902 to 1904 with 1913 gives the following results:

In 1902 to 1904 at Victoria 132 weevils laid 11,863.eggs at the rate
of 89 eggs each, or 2.8 eggs each per day with a maximum of 135 eggs
per female ith 1913 at Victoria 19 weevils in various seasons laid
4,036 eggs at the rate of 212 eggs each, or 5.9 eggs each per day with
a maximum of 358 eggs. In one of the fecundity series in 1913 a
female grandis exceeded even this maximum and laid a total of 456
eggs. This evidence seems to indicate that if there has been any
change in the fecundity of the species it is in the nature of an increase

rather than a decrease.
OVIPOSITION PERIOD.

During the summer a total of 47 females were observed through
the complete oviposition period.. The results of these observations
are summarized in Table XV.

TABLE X V.—Oviposition period of the boll weevil obtained in all experiments.

Number . +
: = Maximum | Minimum | Average
Source of weevils. Season. > a ee period. period. penBe
Days. Days. Days.
Once fertilized grandis females... -- June to September... . 5 61 19 36
Grandis females with complete rec- | July to August.....--- 9 52 17 32.7
ord on copulation.
Hibernated grandis females.....--- deMayatosulyss-beeeo ae 2 55 12 33.8
First generation grandis.......--..- Junestowulyeeeeaa- oe Lie ese | Sos eee 25
Third : generation grandis.......---- July to Seprember Bs ok 3 67 16 47.7
Last of first generation grandis..... August to September... Assen Seon S| sseee oes 59
Fourth generation grandis......--.-|..--- does ease ees 2 44 44 44
EILCWMUTDCTI Ls ase en eee ee September to October. A 34 30 32
Positive crosses of male thurberigz |.-.... Se esopoosooEsace= 3 48 13 33
and female grandis.
Doubtful crosses of male thurberiz | May to June.....-.-.-- 2 49 27 38
and female grandis.
Positive crosses of male grandis and | September to October. 3 52 30 39.3
female thurberiz.
Doubtful crosses of male grandis | June to July.......--- 2 38 29 33.5
and female thurberiz. |
Tics 2s BoA ne aan eee | oh a See eee AT [ownwoh ei alee eee eee
Wieiehtediaverare cst oei2 oe sce o|l sh Ee Se ee S| Ra yore ree | eee ee FE ate 395. 8
INSERT TOTNES Ase Sa ee ge rR ee Jian 'Se Sis See aoe ee ae | reer G72). -4- Sean Me eee
NDT So 85 Caso Ene ae eee lecereene mata ae eee emacs ay Ss aaa 5eoec 125\\ seeee ace

Here it is seen that the period ranged from 12 to 67 days with an
average of 35.8 days for all females. The number of females of the
different classes is too small to permit anything like an accurate
comparison of results. While the pure thurberiz and the crosses
containing females of this variety averaged a slightly shorter time
for the period than the native grandis, this difference is not great
enough to indicate that there is any special significance in it.

—

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 25

Although the 1913 records on the oviposition period did not in any
case approach the maximum recorded period, the average length
was almost 5 days longer than the average of all previously recorded

experiments.
EXTERNAL DEPOSITION OF EGGS.

In all types of breeding series and at all times during the season
females were observed to deposit eggs externally. Usually, when the
eggs were deposited externally, the female was either infertile or
about through ovipositing but not infrequently fertile eggs were
deposited externally by females on the same day they deposited a
number normally. A few observations were made of fertile females
depositing eggs in empty glass tubes. very time this happened the
female would turn and immediately eat the egg. This habit of
eating eggs deposited externally was observed many times and
undoubtedly greatly reduced the number found.

The eggs deposited externally were found in all manner of positions
on the calyx and bracts of squares, some even being found on the
outside of the bracts. When covered with a moist cloth and placed
on damp sand several of the eggs hatched. In one case an egg
hatched within 24 hours after deposition and two others hatched
within 48 hours. As eggs in squares at this time were taking 3 and
4 days to hatch it seems evident that the period for those deposited
externally was shortened by the greater exposure to the heat at the
time. The tissue of the squares surrounding those deposited nor-
mally probably reduces the temperature affecting the eggs.

A number of larvee were observed after hatching from eggs deposited
externally. Although several of these larvee were very near punc-
tures in the square not one was observed to make its way into the
square. ‘They all moved around considerably but died within about
one day after hatching. In one case a larva hatched from an egg
placed about half inside a puncture and died without entering the
square.

Some of these larvee were taken immediately after hatching and placed
in an incision in a square. These larve lived and matured. One
larva hatched from an egg deposited on the petal of a Hibiscus bloom
was placed in an opening ina Hibiscus bud and reached pupation safely.

Many of the eggs deposited externally were not observed for hatch-
ing, so no record can be given on the percentage of these eggs that were
infertile, but in one series of females that were depositing fertile eggs
all eggs deposited externally were kept and records made on the
number hatching. A total of 20 eggs was deposited externally in
this series and, of these, 3 hatched, or only 15 per cent. From this
and the general observations made during the season it seems evident
that by far the greater part of the eggs deposited externally are
infertile, but occasionally fertile eggs are deposited in this manner.

26 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE,

NUMBER OF EGGS DEPOSITED FIRST DAY OF OVIPOSITION.

The number of eggs deposited the first day of oviposition by each
female in all series varied from 1 to 12 with an average of 3 eggs for
the 58 females observed during the season.

For typical grandis the number varied from 1 to 12 with an aver-
age of 3 eggs.

For typical thurberix the number varied from 1 to 10 with an
average of 3.4 eggs.

The number for the mating of infertile female thurberie and male
grandis varied from 1 to 2 with an average of 1.6 eggs. The num-
ber for the mating of infertile female grandis and male thurberrx
varied from 1 to 4 with an average of 2 eggs.

PERIOD FROM THE DEPOSITION OF LAST EGG TO DEATH.

The period from the deposition of the last egg to the death of the
female in all series varied from 10 days to death on the same day that
the last egg was deposited. This death on the last day of deposition
was observed 5 times during the season. The average of the 42 cases
observed was 3.1 days.

For the different series of typical grandis this period varied from
10 days to death on the last day of deposition. The average was
3.2 days.

For typical thurberiz this period varied from 3 to 7 days with an
average of 5.2 days.

For the mating of female grandis and male thurberiz the period
varied from 1 to 5 days with an average of 2.4 days.

For the mating of female thurberie and male grandis the period
varied from 3 days to death on the last day of oviposition. The
average was 1.8 days.

CESSATION OF OVIPOSITION BY HIBERNATED WEEVILS.

In connection with the discussion of early or late planting to escape
the attack of the weevil it is interesting to note the time of cessation
of oviposition by early hibernated weevils. The accompanying
table (Table XVI) shows the date of the last egg deposited by each
of the first twelve hibernated females collected in the spring. Here
it is seen that the last egg ranged from May 29 to July 22.

TaBLe X VI.—Dates of cessation of oviposition of first hibernated females of the boll weevil.

| ates Dal

i stoppe stoppe

Date collected. ovipos- Date collected. ovipos-

iting. iting.
INEST SL Gee aS BORGES ene a rg ent ce ea May .-29.|| May: 20. s.ce5 0.005000 Gos ah ae 2 ee eae July 12
HD OR a ieee ao eaise aS Saver eS June 4 DO se SaaS Te oe ee July 22
ED) ORV a Nea eee ee eNOS Abe ECR in Ca deg June 19 DO vise eu BS a 0 NAR an Sn gs duly 8

TD ee eee OME Dene ie lens Te ee ate June 22 Dow re eae AE Se ee eee

AB Yay tee le Ue SP Re aD AP ae aT Mn ea aU July: LO\| May Osc cee0 eae ea ie aaa mee uaaley Tene 14
May DOSE ee Raine Eee ue Ree Cistaye eye areccter eran June 14 || Earliest date stopped..................... May 29
IE) Oe ee ROO a We Dee ca tape cine June 15 || Latest date stopped.._.-.-.--2. 5.222 Ss July 22

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 27

DEPENDENCE OF REPRODUCTION UPON FOOD.

The studies of the feeding habits of the weevils in relation to mal-
vaceous plants other than cotton and Thurberia have served to throw
some further light on this subject. Many weevils were kept on cotton
leaves only from emergence to death, but only one pair was observed
in copula and not a single egg was found; but shortly after such
females were transferred to squares or bolls they would start ovi-
positing more or less normally. The possibility of the shape of the
square or boll being a mechanical stimulus to oviposition was con-
sidered for some time, but later in the season this idea was discarded.
A female which had been fed only on the blooms of Hibiscus syriacus
from emergence deposited a fertile egg on an open petal of a bloom.
Then shortly after this several females were observed to oviposit in
empty glass tubes. So it seems that oviposition is simply a question
of food and fertility, although the element or elements needed for
sexual maturity are not limited to cotton squares and bolls. This
element is evidently not present in cotton foliage in sufficient quanti-
ties, but is present in varying amounts in cotton squares, bolls, and
blooms, Hibiscus syriacus blooms, and also blooms of Callirrhoé
_involucrata and C. pedata.

DEVELOPMENT.

Only a few observations were made on the individual stages of
development, although much work was done upon the whole period of
development. The length of the stages was obtained by repeated
examinations to learn the dates of transformation.

Incubation period.—The data on the egg stage are summarized in
Table XVIL.

TaBLe XVII.—Incubation period of the boll weevil.

Period.
Number E Mean
Date of oviposition. ofindi- | 4,88 tempera-
viduals. y Mini- Maxi- | 4 ie ture
mum mum CHGS:
Deposited normally: | Days. Days. Days. SOF,
UNO) Boe ea ote Ae Ge SER ees EMRE sea 9 18 2 2 2.0 88.5
DARE ARE yaa aay tao teal er NR 8 17.6 2 3 22 87.6
Pays ens Mea tan cee tarsG VDA ER SINS (AN 20 53.8 2 3 2.69 86.8
Pal he: SACS aE Ee Peet dee te ase 17 48. 28 2 4 2.84 86.1
Sepitpl One eps cre aay awl Cae BN eae 11 55.0 5 5 5.0 74.1
1b) sb pare ened AE. Shee ei) sr pad es ee EIN 23 131.1 5 6 5.7 73.1
FA Ae aes Ae ia Coe ea ne oo eS Sh 24 139.2 5 6 5.8 71.9
7A WES Ce Erte ES OP CaO ae 9 50. 4 5 6 5.6 70.9
22.... ED USE IE AN HOA eae ONO 17 81.6 3.5 5.5 4.8 72.9
Total and average................... 138 594.9 2 6 ZAR ol ae ie
Doposited externally:
Mayer 2 Once mennen aace eee ane ated 1 1 1 1 1 77.4
BANU fo ord ()retead een coat sre RE atin Aa ele 2 4 2 2 2 86.4
Totaliand:average. 222. s-2 5 ss5 525) 3 5 1 2 15Gho | Seeenecoes

28 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE.

By this table it is noted that normally deposited eggs developed in
2 days at 88.5° and in 5.8 days at 71.9°, while eggs deposited externally
and therefore directly exposed to the changes of air temperature
developed in 1 day at 77.4° and in 2 days at 86.4°.

One weevil fed on flowers of Hibiscus syriacus deposited an egg
externally on September 21. This egg hatched in 4 days at a mean
temperature of 71.1°.

Larval period.—Only 26 larvee were observed through this stage and
they averaged 6 days with a minimum of 5.1 days and a maximum of
7.1 days at a mean temperature of 84.7°. One greatly retarded indi-
vidual not observed to pupation required over 10 days for the period.

Pupal period.—Only 7 observations of the pupal period were made.
The average period was 4.63 days, with a minimum of 4.38 days and
a maximum of 5.38 days, at a mean temperature of 83.6°.

TOTAL DEVELOPMENTAL PERIOD.

The data for the total developmental period are presented in Table
XVIII. Records of the development of 1,513 individuals indicate
a very slightly shorter period for the females than the males. These
various records are not strictly comparable until correlated with the
climatic records.

TaBLe XVIII.—Data on the developmental period of the boll weevil.

TEXAS WEEVILS.

tH = '

oO We! (>)

Males Females 5 Es =

Nature of Larval _ Period of uy sah an WS eS oe ee B ae AA
weevils. food. oviposition, | vSe a) secs i) Seo tS) eae |) Se al eee

: f2| s>|S2 lg2| 92/52/58 | S 5

B55) So |} eo [38] 2S | ec lo S >

mole. [dele | | Onl eee en Gale
Days. Days Days.
First generation...| Cotton | May 19-31....... 54 884 | 16.3 | 50 804 | 16.0 | 104 | 1,688 | 16.2

squares.
DD OSes See aie SCOP a reh4| JUNO peace 72 | 1,206 | 16.7 | 75 | 1,249 | 16.6 | 147 | 2,455 | 16.7
DORE Sees s --.do....| June 6-10....... 57 895 | 15.7 | 44 700 | 15.9 | 101 | 1,595 | 15.7
DOM eee ie ees Ed Ose ssh WUNer—loeesae 48 729 | 15.1 | 33 493 | 14.9 81 | 1,222) 15.0
OB eee one oe --.do....| June 16-20. ..... 27 379 | 14.0 | 34 470 | 13.8 61 849 | 13.9
1D Yo ae eeeees ---do....| June 21-25...... 36 477 | 13.2 | 40 526 | 13.1 76 | 1,003 | 13.1
DD OMe eae ee --.do....| June 26-30...... 33 447 | 13.5 | 32 418 | 13.0 65 865 | 13.3
HD) QW ee Is SeeGOn. ae Ubyot Gases eee 12 176 | 14.6 | 13 184 | 14.1 25 360 14.4
Second generation .|...do....| June 17-30... ..- 41 552 | 13.4 | 42 562 | 13.3 83 | 1,114] 13.4
Offspring single |...do....; June 25-July 12 .| 13 178 | 13.7 ; 10 134 |.13.4 23 312) |> 13.5
pair. ee

Second generation .|...do....| Aug.19-Sept.26.| 8 128 | 16.0] 5 81 | 16.2 13 209 | 16.0
Third generation. .|...do....| July 7-10........ 3 39 | 13.0] 5 68 | 13.6 8 107 | 13.3
Fourth generation .|...do....| July 27-30....... 4 52 1}13.0| 4 56 | 14.0 8 108 | 13.5
Fifth generation..-|...do....| Aug.20-Sept.9..| 8 133 | 16.6 | 5 72 | 14.4 13 205 | 15.7
Sixth generation...|...do....] Sept. 9-17....... 3 56 | 18.6} 3 57 | 19.0 6 113} 18.8
DOR sees See GORs 22 OCbE Beet caste ae Ree a epee: 1 21 | 21.0 1 PA Ne PIS
Seventh generation |...do....| Oct. 11-14....... 2 43} 21.5] 1 21 | 21.0 3 64 | 21.3
Miscellaneous series|...do....| July 3-Aug. 2...|118 | 1,544 | 13.1 | 91 | 1,170 | 12.8] 209 | 2,714 | 13.0

——.}$|§ —— | —— | | | — | | |

True grandis.|...do....| May-Oct.....-... 539 | 7,928 | 14.7 |488 | 7,086 | 14.5 |1,027 |15,014 | 14.6

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 29

Taste XVIII.—Data on the developmental period of the boll weevil—Continued.

ARIZONA WEEVILS.

Nature of
weevils.

First generation. - -

True thurbe-
71k.

Male grandis by fe-
male thurberizx.
First genera-
tion.

tion.

Male thurberixe by
- female grandis:
First genera-
tion.

tion.

Total of all
varieties.

Larval
food.

_.| Sept. 3-10

ae June 16-30
S|) diwlhysleyeeecsases

Period of
oviposition.

ete reese

May, Sept.......

| Sept. 7-Oct. 2...
.| June 6-July 3...

July 2-15........

Sept. 5-Oct. 4..-
May 30-June 15. .

=" [oot 1

oP) AS CP)

Males Females. z é 2

a l=.lasl8 )2.|eleze| Pelee
2d} pu 8 = 2gjl/ bu ao] u4o}] od oar

HS) oF |B 18o| oF | SH] S Ss ®

BB) °S8 | Fs i155) PS | eels 6 >

VA 42/7" | & am] = a
Days. Days Days.
20 353 | 17.6 | 12 207 | 17.2 32 560} 17.5
2 BS ili MONO n | Sas es ieee ieee te 2 38 | 19.0
1 LS USI On SS sales bos ae oes 1 18 | 18.0
3 55 | 18.3 2, Ot |S o 5 92 18. 4
2 49 | 24.5 3 76 | 25.3 5 125 | 25.0
28 513 | 18.3 | 17 320 | 18.8 45 833 | 18.5
11 218 | 19.8 | 13 228 | 17.5 24 446 18.5
20 270 | 13.5 | 19 257 | 13,5 39 527 | 13.5
15 212 | 14.1 |} 11 157 | 14.2 26 369 14.1
46 700 } 15.2 | 43 642 | 14.9 89 | 1,342 15.0
22 387 | 17.5 | 15 265 | 17.6 37 652 | 17.6
83 | 1,415 | 17.0 | 73 | 1,049 | 14.3 | 156 | 2,464 | 15.7
35 453 | 12.9 | 39 510 | 13.0 74 936 13.0
17 208 ! 12.2 | 18 226 | 12.5 35 434 | 12.4
21 293 | 13.9 | 29 389 | 13.4 50 682 | 13.6
178 | 2,756 | 15.4 1174 | 2, 439 | 14.0 352 | 5,195.| 14.7
791 |11,897 | 15.0 |722 10,487 | 14.5 |1,513 |22,384 | 14.7

The total developmental period was also tested in the buds of
Hibiscus syriacus during September and October.
varied from 15 to 17 days, with an average of 16 days, and 2 grandis
gave a period of 17 and 18 days, or an average of 17.5 days.

GENERATIONS.

Three thurberice

In order to determine definitely the possible number of genera-
tions of weevils in one season two series were carried through the

breeding season.

These were to determine the maximum and mini-

mum number of generations in cotton squares from the first hiber-
nated females to emerge in the spring.

In the maximum series the first eggs from the first hibernated
females found were saved for the emergence of the adults.

first of these adults to emerge were mated, their first eggs saved, and
Table XIX shows the results of this

so on through each generation.

series.

The

30 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE,

Tasie XIX.—Number of generations of the boll weevil—maximum series on squares.
[First generation from first eggs of females that emerged from hibernation May 8 to 10.]

Period from

Mean tem- :
: maturity to
Generation. Date. perature for maturity

period.’ (about).

First generation: Sor Days.

1 DF easTs Fe ( eee Aen ig eerste arte suai mie rales Gene ors Mary: 3 VOR D4 i ae Oe cea ae le conor

Genera tionanavurests 5 4252 = ses Stee se eet ec ey pieere ate June 4-8 78.2 28
Second generation:

Healer fis. 7 snes Dee Re Te Pah aa eee ak eae June 17522) Sse een | Sea

Generabionvmature, sk ss oae sik Sy ey ee eee July 1-4 80.1 26
Third generation:

A feasts Fe (6 RS a oe Se ee ec eRe carey Aer ou a a Mal aE Tulyee (10 ee as ee cee mre eercte

Generation mature......-.. Se eer see IO Rn Be 2 July 20-22 84.3 19
Fourth generation: ;

TE SHG ee err ee os Bence ec er Se Ee ee Cc as ea ey July 27-30 theses eae eee ees

Genera tiomerm a tine se ase se aa eer Sh ee te os eases Aug. 9-11 87.5 20
Fifth generation: |

Dye tay FE WEG Ue RI BS Oa ear aes ml na tN SSIS ah Ns She I a Aug. 19-2352 Sass ce |taeetecneciene

Generationimatunes. 25 oes ei Fa cee sane tere ae Sept. 3-5 85. 2 25
Sixth generation:

IOs) GNC VARs SBE AA ee ee aS Ree MEAs nt Seco daoE sce aeea se BaSe Sept.- 8-10) |. o2o5. aes eee

Generatiomsmature:<% 5 est eee ee eed bese Pea ee ee Sept. 27-29 76.5 24
Seventh generation:

I DYES) NG Ee ees Seer ol aM APE aot SPIE ay Oe EES ver ere ae. 5 Octnk) (qllsies sss: . 2 ee eee

Generations matunete soso. eos ee ce ee ean anaes Nov. 2-4 69.8 36

1 The period referred to here is that from the average time of emergence of a generation to the same
time in the next generation.

The weevils were very unusually late in emerging from hiberna-
tion at Victoria in the spring of 1913, the first being found on May 8.
This is at least two or three weeks later than the usual time. As a
result, nearly one complete generation was cut off the first of the
season. ‘The last generation secured in the breeding series was the
seventh. The adults of this generation emerged. November 2 to 4.
At this time the cool weather had practically stopped all breeding
in both cages and field, and this was considered to be the last gener-
ation. However, the weather became warmer in the latter part of
November and December, and on the 26th of December Mr. J. D.
Mitchell found breeding in progress in the field. This was evidently
a case of an extra generation caused by the unusually warm weather
after the starting of hibernation. The maximum number of genera-
tions In squares at Victoria in a normal season is evidently seven or
eight.

The minimum generation series was conducted quite differently.
The last eggs were secured from the hibernated females used in start-
ing the maximum series. The last adults reared from these eggs were
mated and their last eggs secured. The results of this series are
shown in Table XX. The last adults of the second generation did
not mature until October 13 to 15, and as these certainly would enter
hibernation this was considered as the minimum number of genera-
tions from the first hibernated females. As the last females to
emerge from hibernation in the spring would continue ovipositing
much longer and the last weevils of the first reared generation would
mature much later in the season, it seems quite possible for weevils
of the first generation to enter hibernation in the fall.

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 31

TaBLE XX.— Number of generations of the boll weevil—minimum series on squares.

[First generation from last eggs of females that emerged from hibernation May 8 to 10.]

Period from
maturity Mean tem-

Generation. Date. : perature
to maturity sera
(about). for period.
First generation: Days. pele
VSR SYENEAS TEN (6 Le ES Beate gates Aa 2A net nea ey Ste ARES nt ci tee arent DULY SAH 1G scosi os es lao a ees
Generation atime sree <eiss cer oe ese ie as else July 29-30... 81 80.7
Last generation:
ILE RE PRES EWG LSE PS Ser Se a Oc Ne I Ne Ee Se See a Sept: 26-802 osesaaee Pee oe ete
GenerahionWmanure cic sesr is Fo. se ye See ao See oe eee e Oct. 13-15... 78 80.7
HIBERNATION.

The hibernation of variety thurberiz in bolls of Thurberia is longer
than any other phase of this phenomenon for the species. The adults
mature in their cells before December, but remain therein until August
or later around Tucson, Ariz. When removed from the cells they
begin activity immediately.

NATURAL CONTROL.

Parasitism.—The parasitism of native weevil stages at Victoria
during the season was very slight. In spite of the large numbers of
infested squares and bolls collected in the field and held for the emer-
gence of weevils, not a single parasite was reared. Several hundred
infested squares and bolls were opened during the season and only
one parasite larva was found.

Late in the season two lots of squares were sent to the writer from
Tallulah, La., by Mr. G. D. Smith. These were placed in cages for
the emergence of adults and five species of parasites emerged. These
were: Bracon mellitor Say; Catolaccus wncertus Ashm.; Catolaccus
hunteri Cwfd.; Cerambycobius cyanceps Ashm.; EHurytoma tyloder-
matis Ashm. Of these Bracon was much the more abundant.

Krom the thurberxex imported from Arizona only one parasite was
reared at Victoria. ‘This was a specimen of Hurytoma sp. which had
parasitized a weevil larva.

During September what threatened to be a serious outbreak of a
mite (probably Pediculoides sp.) appeared in the various breeding
series. This infestation spread rapidly over many of the shelves
where immature stages of weevils were being reared and soon killed
a considerable number of these. This infestation was evidently con-
trolled by the cool weather and no further trouble was experienced.

Messrs. Schwarz and Barber found in Thurberia bolls two individ-
uals parasitized by Ichneumonoidea.

Disease—During the latter part of the season a curious epidemic
of deaths of newly emerged weevils occurred in one breeding series.

32 BULLETIN 231,-U. S. DEPARTMENT OF AGRICULTURE.

Little attention was paid to the deaths at first, but m about three
days nearly all weevils in this series had died. It was then noted
that instead of presenting the usual appearance of death the weevils
became very dark in color, almost black, in fact. On touching these
weevils it was found that they were very soft and the body contents
were liquified. This liquid had the usual dark color and character-
istic odor of flacherie of lepidopterous larve. The source of the
seemingly diseased weevils was investigated, and it was found that
all came from squares kept in a California breeding box which had
contained lepidopterous larvee infected with fiacherie only a short
time previously. Two of the dead weevils were submitted to Dr.
G. F. White, of this bureau, for bacteriological examination, and he
reported as follows:

In the examinations made the findings in the two specimens are the same. The
direct examination shows the presence of a very large number of microorganisms,
Which seem to be bacteria. The appearances suggest that most of these organisms
belong to one species. Comparatively few colonies appeared in plate cultures made
irom the material. There is some indication, thereiore, that the trouble is bacterial
in origin. These results can be interpreted, of course, only as suggesting the pos-
sibility.

While the results secured by Dr. White are by no means conclu-
sive, they do, as he says, suggest the possibility of a bacterial dis-
ease of the boll weevil. Although it is but a mere possibility, there
is evidently an opportunity for considerable profitable investigation
of the subject.

BEHAVIOR OF LOUISIANA WEEVILS AT VICTORIA.

Late in the season a number of infested squares were imported
from Tallulah, La., in order to test the weevils emerging from them in
their various life functions in comparison with Texas weevils. As
the work was interrupted by the cool weather very little was learned
from the series, but some results of interest were secured. Four
pairs of weevils were mated on cotton squares immediately after
emergence and tested for fecundity. These weevils emerged on
September 18 and on September 20 one female deposited 1 egg and
another deposited 2. The latter female deposited another egg on
September 22, and then neither of these two deposited any more eggs
before the series was closed on October 29. The third female lived
through the same period and did not deposit an egg. The fourth
female emerged September 20, deposited 1 egg on September 22,
and then waited 14 days before depositing another. Then deposi-
tion started normally and 37 eggs were laid in the next 23 days.
These results are very peculiar, especially the fact that three out of the
four females began deposition on the second day after emergence and
then stopped; two of them permanently and one for a period of
14 days.

RECENT STUDIES OF THE MEXICAN COTTON BOLL WEEVIL. 38

The eggs deposited were tested for the maturing of adults, but
none emerged, possibly owing to the cold weather. Native weevils
were maturing in small numbers under the same conditions at this
time, but as the number tested was so small there may not be any
significance in this fact.

These weevils were also tested for their ability to subsist on a
diet of Hibiscus syriacus. The detailed results of this test have been
published in the paper on the feeding habits of the weevils. As only
blooms were available no tests were made of the ability of these
weevils to breed in the buds of this plant, but they seemed as well
adapted to the plant as the native and Thurberia weevils.

DEVELOPMENT OF THURBERIA THESPESIOIDES.

On May 21 a supply of seeds of Thurberia from the Santa Rita
Mountains, Ariz., were planted at Victoria. A bed of rather sandy
soil was selected in a well-drained situation. On May 26 the first
seedling appeared above the ground and 11 plants were visible by
Junel. Although over 100 seeds were planted only these 11 sprouted.

These plants grew rather rapidly for a couple of months but
formed no lateral branches of any consequence. The growth was
entirely upward and the stems were very thin, causing the plants to
require staking to prevent drooping. About August 20 a number
of fruiting branches appeared near the top of the plants and these
developed very rapidly. At this time the larger plants were 34
feet in height. On August 26 the first bud was observed and many
more appeared daily for a period of about three weeks. Then
fruiting was discontinued for a couple of weeks followed by the
production of more fruiting branches. These plants continued to
erow with intermittent formation of buds until the observations
were discontinued on November 6. At this time several of the

_ plants were more than 4 feet in height.

At Batesburg, 5. C., Mr. E. A. McGregor planted about 100 of these
seeds in a sandy bed. Not a single one of these appeared above the
soul.

At Tallulah, La., Mr. G. D. Smith planted a number of seeds
and only one sprouted. ‘This plant lived through the season.

EXAMINATION OF THURBERIA BOLLS.

On March 10, 1914, the writer examined part of a lot of infested
Thurberia bolls which had been collected by Messrs. Schwarz and
Barber at from 4,500 to 5,000 feet altitude in Stone Cabin Canyon,
Santa Rita Mountains, Ariz., on December 6, 1913. These bolls
were shipped to Washington shortly after collection and placed in a
cool cellar there until the day of examination. Seventy-seven of

34 BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE,

the bolls yielded a total of 84 live weevils; one containing 3, 5 others
containing 2 each, and the remainder containing 1 each. One boll
had been completely eaten out by a bollworm, and another showed
signs of weevil injury and a braconid parasite cocoon. Two dead
pupe and 2 dead larve were found in 4 other bolls. Their
deaths were in all probability due to climatic causes. The remaining
boll contained signs of weevil larval work, but no insects, either
dead or alive, were found. One boll which contained a weevil adult
also contained a tiny, light-green lepidopterous larva.

Of the 84 weevils found in the bolls, 52 were males and 32 were
females. One additional male was found crawling among the
bolls when the bag was opened. Those in the bolls were all tightly
sealed in the pupal cells and were usually quiet when first opened.
As soon as the weevils were exposed to the air they became quite
active and remained that way.

The peculiar feeding habit of the larve of these weevils is certainly
well adapted to destroying the maximum number of seeds in a
boll. They do practically all their feeding in the center of the
boll and form the pupal cells in this same place. Owing to the
arrangement of the seeds this location of the larva enables it to
injure practically every seed in the boll instead of injuring those
of one lock as is usual with the cotton weevils.

On March 12, 1914, another lot of infested Thurberia bolls were
examined. These were collected by Mr. Schwarz in a small canyon
between Stone Cabin and Sawmill Canyons, Santa Rita Mountains,
Ariz., on December 7, 1913, at about 3,900 feet altitude. The bolls
were sent to Washington soon after collection and had been in a
cool cellar from that time until examined.

Examination of 39 of the bolls showed 2 clean and the remainder
infested. Thirty-three bolls yielded 36 live weevils, 3 bolls contain-
ing 2 each. Three dead adults (2 females and 1 male) were found
in as many bolls. These deaths were probably due to climatic causes.
One boll was found which showed signs of larval injury but the larva
was not to be found. No signs of parasitism were found. One
lepidopterous larva like the one noted in the preceding lot was found
in a boll with a weevil. The live weevils consisted of 18 males and
18 females.

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