• TABLE OF CONTENTS
HIDE
 Front Cover
 Front Matter
 Introduction
 Equipment
 Control of temperature and humidity...
 Experimental data, 1927-28
 Experimental data, 1928-29
 Conclusions
 Literature cited
 Back Cover






Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 240
Title: Hibernation of the cotton boll weevil under controlled temperature and humidity
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026679/00001
 Material Information
Title: Hibernation of the cotton boll weevil under controlled temperature and humidity
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 19 p. : charts ; 23 cm.
Language: English
Creator: Grossman, Edgar F
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1931
 Subjects
Subject: Boll weevil -- Wintering -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 19.
Statement of Responsibility: by Edgar F. Grossman.
General Note: Cover title.
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00026679
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924093
oclc - 18204468
notis - AEN4697

Table of Contents
    Front Cover
        Page 1
    Front Matter
        Page 2
    Introduction
        Page 3
    Equipment
        Page 4
    Control of temperature and humidity equipment
        Page 5
    Experimental data, 1927-28
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    Experimental data, 1928-29
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
    Conclusions
        Page 19
    Literature cited
        Page 19
    Back Cover
        Back Cover
Full Text


October, 1931


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
Wilmon Newell, Director






HIBERNATION OF

THE COTTON BOLL WEEVIL

UNDER CONTROLLED

TEMPERATURE AND HUMIDITY


By EDGAR F. GROSSMAN


CONTENTS


INTRODUCTION .. .... ... -----. ...- ..... .
EQUIPMENT ............. ---------.......
CONTROL OF TEMPERATURE AND HUMIDITY..........
EXPERIMENTAL DATA, 1927-28 ..................-...
EXPERIMENTAL DATA, 1928-29 ......................
CONCLUSIONS .......... --------....


PAGE
.. ...........-.-. -.....-------------... -.. 3
... ..... ---. .............. 4
.... ..... -...-- .. --...........- 5

..................... ...... ............... 613
..................... ........ ......... 13
-. ...- --- --- -..- ....... ..-- ---. 19


TECHNICAL BULLETIN






Bulletins will be sent free upon application to
the Agricultural Experiment Station,
GAINESVILLE, FLORIDA


Bulletin 240











BOARD OF CONTROL

P. K. Yonge, Chairman, Pensacola
A. H. Blanding, Bartow
W. B. Davis, Perry
Raymer F'. Maguire, Orlando
Frank J. Wideman, West Palm Beach
J. T. Diamond, Secretary, Tallahassee


EXECUTIVE STAFF

John J. Tigert, M.A., LL.D., President of the
University
Wilmon Newell, D.Sc. Director
H. Harold Hume, M.d., Asst. Dir., Research
Sam T. Fleming, A.B., Asst.Dir., Administration
J. Francis Cooper, M.S.A., Editor
R. M. Fulghum, B.S.A., Assistant Editor
Ida Keeling Cresap, Librarian
Ruby Newhall, Secretary
K. H. Graham, Business Manager
Rachel McQuarrie, Accountant


MAIN STATION, GAINESVILLE
AGRONOMY
W. E. Stokes, M.S., Agronomist
W. A. Leukel, Ph.D., Associate
G. E. Ritchey, M.S.A., Assistant*
Fred H. Hull, M.S., Assistant
J. D. Warner, M.S., Assistant
John P. Camp, M.S., Assistant
ANIMAL HUSBANDRY
A. L. Shealy, D.V.M., Veterinarian in Charge
E. F. Thomas, D.V.M., Assistant Veterinarian
R. B. Becker, Ph.D., Associate in Dairy In-
vestigations
W. M. Neal, Ph.D., Asst. in Animal Nutrition
P. T. Dix Arnold, B.S., Assistant in Dairy In-
vestigations
CHEMISTRY
R. W. Ruprecht, Ph.D., Chemist
R. M. Barnette, Ph.D., Associate
C. E. Bell, M.S.. Assistant
J. M. Coleman, B.S., Assistant
H. W. Winsor, B.S.A., Assistant
H. W. Jones, M.S., Assistant
ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural Economist
Bruce McKinley, A.B., B.S.A., Associate
M. A. Brooker, Ph.D., Associate
Zach Savage, M.S.A., Assistant
ECONOMICS, HOME
Ouida Davis Abbott, Ph.D., Head
L. W. Gaddum, Ph.D., Biochemist
C. F. Ahmann, Ph.D., Physiologist
ENTOMOLOGY .
J. R. Watson, A.M., Entomologist
A. N. Tissot, Ph.D., Assistant
H. E. Bratley, M.S.A., Assistant
E. F. Grossman, M.A., Asso., Cotton Insects
P. W. Calhoun, Assistant
HORTICULTURE
A. F. Camp, Ph.D., Horticulturist
Harold Mowry, B.S.A., Associate
M. RB. Ensign, M.S., Associate
A. L. Stahl, Ph.D., Assistant
G. H. Blackmon, M.S.A., Pecan Culturist
C. B. Van Cleef, M.S.A., Greenhouse Foreman

*In cooperation with U.S.D.A.


PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist
George F. Weber, Ph.D., Associate
R. K. Voorhees, M.S., Assistant
Erdman West, M.S., Mycologist


BRANCH STATIONS

NORTH FLORIDA STATION, QUINCY
L. O. Gratz, Ph.D., Associate Plant Pathologist
in Charge
R. R. Kincaid, M.S., Asst. Plant Pathologist
W. A. Carver, Ph.D., Asso. Cotton Specialist
R. M. Crown, B.S.A., Asst. Agronomist, Cotton
Jesse Reeves, Farm Superintendent

CITRUS STATION. LAKE ALFRED
John H. Jefferies, Superintendent
Geo. D. Ruehle, Ph.D., Asst. Plant Pathologist
W. A. Kuntz, A.M., Asst. Plant Pathologist
B. R. Fudge, Ph.D., Assistant Chemist
W. L. Thompson, B.S., Assistant Entomologist

EVERGLADES STATION, BELLE GLADE
R. V. Allison, Ph.D., Soils Specialist in Charge
R. W. Kidder, B.S., Farm Foreman
R. N. Lobdell, M.S., Associate Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
H. H. Wedgeworth, M.S., Asso. Plant Path.
B. A. Bourne, B.S., Asso. Plant Physiologist
J. R. Neller, Ph.D., Associate Biochemist
A. Daane, Ph.D., Associate Agronomist
M. R. Bedsole, M.S.A., Assistant Chemist
Fred Yount, Office Assistant

SUB-TROPICAL STATION, HOMESTEAD
H. S. Wolfe,Ph.D.,Asso. Horticulturist in Chg.
L. R. Toy, B.S.A., Asst. Horticulturist
Stacy O. Hawkins, M.A., Assistant Plant
Pathologist


FIELD STATIONS

Leesburg
M. N. Walker, Ph.D., Asso. Plant Pathologist
W. B. Shippy, Ph.D., Asst. Plant Pathologist
K. W. Loucks, M.S., Asst. Plant Pathologist
C. C. Goff, M.S., Assistant Entomologist
J. W. Wilson, Ph.D., Assistant Entomologist
Plant City
A. N. Brooks, Ph.D., Asso. Plant Pathologist
R. E. Nolen, M.S.A., Field Asst. in Plant Path.
Cocoa
A. S. Rhoads, Ph.D., Asso. Plant Pathologist
Hastings
A. H. Eddins, Ph.D., Asso. Plant Pathologist
West Palm Beach
D. A. Sanders, D.V.M., Associate Veterinarian
Monticello
Fred W. Walker, Assistant Entomologist
Bradenton
David G. Kelbert, Asst. Plant Pathologist








HIBERNATION OF

THE COTTON BOLL WEEVIL

UNDER CONTROLLED

TEMPERATURE AND HUMIDITY
By EDGAR F. GROSSMAN

INTRODUCTION
The temperature and humidity conditions through which the
Mexican cotton boll weevil (Anthonomus grandis Boh.) lives in
its natural hibernation quarters in the woods or fields vary
greatly from day to day throughout the winter in Florida. Like-
wise, temperature and humidity vary in the hibernation cages
which are variously placed on the ground either in dense woods,
in light woods, or in the open field. A careful analysis of the
effect temperature and humidity have on the emergence of the
boll weevil from its natural hibernation quarters or from the
debris which has been placed in hibernation cages yielded meager
information (3)'. The fact that weevils emerge from hiberna-
tion to subsequently reenter dormancy while under observation
in hibernation cages (5) renders the data secured from the
hibernation cages incomparable with the field data which are
obtained by counting the weevils as they appear in a cotton
field after emerging from their natural hibernation quarters in
neighboring woods. Whether or not weevils emerge from and
reenter hibernation in their natural hibernation quarters when
optimum temperatures and humidities occur can only be assumed
by analogy.
It was found, however, that the weevils emerged from hiberna-
tion and made their appearance in the field in a manner which
was definitely correlated with the rise and fall of the minimum
temperatures during June, regardless of the fluctuations of the
temperature during the winter and early spring (3). Weevils in
ACKNOWLEDGMENTS
Acknowledgment is due A. F. Camp, under whose direction the low tem-
perature incubator was constructed; P. W. Calhoun, who operated the
incubator; and C. L. Driggers, who counted the majority of the hibernating
weevils.
'Reference is made by number (italic) to Literature Cited, page 19.







Florida Agricultural Experiment Station


hibernation cages, on the other hand, appeared to respond to
increased minimum temperatures by quitting their winter quar-
ters whenever warm days occurred during the entire winter
and spring periods (3, 5). A comprehensive study of the effects
of humidity on the emergence of the weevil from either its nat-
ural quarters or its quarters in the hibernation cage yielded no
definite information relative to the possible effects which either
increased or reduced humidity may exert on the weevil. Con-
sequently a study of the effects which temperature and humid-
ity have on the boll weevil was planned in which uniform tem-
peratures and relative humidity were maintained in artificial
hibernation quarters in which boll weevils were placed.
The debatable question relative to the presence of groups of
weevils which prepare themselves for and enter hibernation
in broods in the cotton fields in autumn also was considered.

EQUIPMENT

A large cork-insulated incubator was built in such a manner
that four independently controlled compartments, each measur-
ing 3x3x4 feet, were available for experimentation. Two alter-
nate compartments were equipped with brine coils which were
cooled by a two-ton capacity refrigeration machine. All of the
compartments were equipped with heating coils regulated to
prevent super-cooling. Each compartment was supplied with a
fan which kept the air well agitated, thereby preventing the
formation of air-pockets in which the temperatures vary. Con-
trolled temperatures between 320F. and 850F. were available
for experimentation.
The compartments were also equipped with automatic record-
ing thermographs. These instruments recorded any fluctuations
of the temperature desired to be maintained. In addition to
the thermographs a multiple-pen recording bulb thermometer
was installed on the outside of the low temperature incubators.
Since the bulbs were centrally located within the compartments
while the dial remained on the outside, temperature readings
could be made without necessitating the opening of the doors.
Preliminary experimentation (2) was conducted with desic-
cators which contained definite percent of sulphuric acid in
water to maintain constant humidities ranging from 1 percent to
100 percent relative humidity. These tests indicated that a rel-
ative humidity between 79 percent and 85 percent appeared to






Bulletin 240, Weevil Hibernation, Controlled Conditions 5

be the optimum range for prolonged longevity of the boll weevil.
Thereafter the desiccators were discarded and each compartment
was equipped with water trays which maintained a fairly con-
stant optimum relative humidity throughout each compartment.
A hygrograph was used for measuring the relative humidity
until it was found that negligible fluctuations occurred either
below or above the desired constant. The optimum relative
humidity extending from 79 to 85 percent was obtained by the
use of water pans over which the agitated air from the fans was
blown. Pans measuring about five inches in width and three feet
in length filled with water sufficed. In addition to serving as
humidifiers they afforded means of collecting the drippings from
the brine coils which were not inclosed. As a consequence it
was rarely necessary to add water to the trays after they had
been filled.
All boll weevils used for these hibernation studies were con-
fined in small cylindrical, 16-mesh screen cages which measured
about one and one-half inches in diameter and five inches in
length. Both ends of the screen cylinders were fitted with corks.
The compartments were equipped with shelves on which the
small screen cages could be placed in such manner that they were
all exposed to the same temperature and relative humidity con-
ditions.
In 1927, over 50,000 boll weevils were used in the incubators.
They were captured in fields at Gainesville, Florida. In 1928,
52,484 weevils were used; 21,589 of this number were captured
near Omega, Georgia, while the remainder were captured in
fields at Gainesville, Florida.

CONTROL OF TEMPERATURE AND HUMIDITY
EQUIPMENT

Numerous observations indicated that the boll weevil becomes
inactive at temperatures between 500F. and 600F. and that the
majority of the weevils which were examined appeared to be-
come dormant at 55F.
The thermo-regulators for both refrigeration and heating were
so adjusted in each compartment that constant temperatures of
470F., 600F., and 810F. were maintained. Two of the four com-
partments were maintained at 470F. Of these three tempera-
tures, one, 47'F., is well below the point necessary for inducing
hibernation, another, 60F., rests on the upper border line of boll






Florida Agricultural Experiment Station


weevil inactivity, and the third, 810F., is well above the point
of inactivity. The temperatures fluctuated but little after pre-
liminary adjustments had been made. Charts obtained from
automatic recording thermographs within the compartments in-
dicated that fluctuations of not more than 2 degrees Fahrenheit
above or below the desired temperatures were largely due to the
frequent examinations of the apparatus and the constant care
taken in keeping all of the points of the thermo-regulators well
polished. The dial readings of the temperatures which were se-
cured from the multiple-pen recording thermometer registered
the temperature within the compartments without the necessity
of opening the compartment doors. There was relatively little
temperature disturbance noted, however, when the doors were
opened.
After preliminary tests in which varying sizes of water-pans
with and without lamp-wicks were used, no difficulty was at-
tendant upon the maintenance of the desired relative humidity,
which was maintained between 79 percent and 85 percent.

EXPERIMENTAL DATA, 1927-28

Large numbers of boll weevils were collected during a period
from August 26 to December 11, 1927. During this time a total
of 46 groups of weevils were captured for use in the compart-
ment which was maintained at 470F. and between 79 percent
and 85 percent relative humidity.
The first group of 641 weevils was caught on August 26, 1927.
The weevils were placed in small wire cages, 10 specimens to
each cage, which in turn were placed on a shelf in the compart-
ment. One other group was placed in the same incubator on
August 27. In September 16 groups, in October 19 groups, in
November 8 groups, and in December 1 group were placed in
the incubator. In a few of the large groups as many as 100
weevils were placed in a single screen cage, though generally not
over 20 specimens were placed in a cage.
All of the weevils in each group of cages were examined two
or three times a month. The dead weevils were removed from
the cages and their number was recorded. In view of the fact
that in earlier experiments weevils were repeatedly removed
from hibernation and allowed to reenter dormancy as many as
12 times in one day without noticeably affecting their longevity,
the weevils were activated by removing them to room tempera-





Bulletin 240, Weevil Hibernation, Controlled Conditions 7

ture (700F.) while separating the dead from the living. These
counts were continued until all of the weevils were dead.
The dates on which the 46 groups of weevils were placed in
the incubator, the number of weevils in each group, and the
number which were alive after varying lengths of time, are
presented in Table I.
The data fail to indicate that there were groups of weevils
better prepared for hibernation at one time than at another dur-
ing this three and one-half month period. There appears to be
no correlation between the time of placing the weevils in the
incubator and the length of time they lived after being confined.
This lack of correlation becomes apparent on considering the
fact that the four groups which yielded the longest-lived weevils
were placed in the incubator on October 21, September 21, Oc-
tober 15, and September 15, respectively; that the four groups
which contained the shortest-lived weevils were placed in the
incubator on November 8 and 18, and October 26 and 4, re-
spectively; and that four groups which contained weevils which
lived an average length of time were placed in the incubator on
October 11, November 22, October 5, and September 3, respec-
tively. Evidently there were no broods of weevils in the field
in which the weevils were captured, since there were no indi-
viduals which appeared to be especially prepared for hibernation
during any particular time in August, September, October, No-
vember, or December. The longest-lived weevil in the series,
however, died before 175 days had passed.
Concurrently with the series of boll weevils which was placed
in the compartment maintained at 470F., a series including 15
groups was placed in the incubator maintained at 600F. The
same irregularities which attended the first series were found to
be present in this series also. Individuals in several groups often
lived 50 days longer than the majority of the-weevils which were
included in the group. The longest-lived weevil died after it
had been confined for 169 days. The data secured from this
series are presented in Table II.
Three groups of weevils were placed in the incubator main-
tained at 600F. for two days, after which time they were re-
moved to the compartment kept at 470F. A relatively large per-
cent of the weevils lived for 100 days but the longest-lived weevil
died shortly after 152 days had passed. (See Table III.)
The abrupt change from the temperature in the field (which
ranged from 700F. to 90F.) to 470F. apparently did not affect













TABLE I.-LONGEVITY OF BOLL WEEVILS PLACED IN A CONSTANT TEMPERATURE INCUBATOR MAINTAINED AT 470F.


Date placed in hibernation


21....... -.................
21.... ...............
15... ...................
15 --............................
8 ...........- .......-..... .....
12....--.............-........- ....
10 ---..................
20..... ......... ........
2......... .......... ..-..
24............... ....
16........... ...........
25............... .. ....
28.........- .............
23.....................

28..........................
1328 .................... .....-- ... ...
13 ----------
11...-...-........--..........
22.................................
5.............- ......... .......
3................................
30....----- ........-----
30 -- .-------------------_


Number
weevils
used
15 _


745
443
523
437
1130
739
7
361
470
3428
716
667
1536
1225
1998
586
250
505
3053
55
827
882
2683


----------

63.1


43.3
- .--------










47.9
69.4
38.2
----------
----------


Percent weevils living at specified number of days
Days


50 1 75 1 90 100 110 ) 120


19.1
12.0
8.6
17.5
13.6
12.6
14.3
7.8
6.8
0.8
3.5
2.0
6.2
1.6
5.6
9.2
30.0
6.9
10.5
7.3
14.0
8.6
2.1


7.1
5.2
3.4

3.8
5.0
14.3
1.9
0.2
0.4

1.2
1.5
1.0
1.8
5.1
10.8
3.6
2.3
3.6
3.5
0.8
0.5


0.7
0.7
0.4
1.4
0.2
0.1
14.3
0.3
0.2
0.03
0.1
0.2
0.1
0.1
0.1
0.2
0
0
0
0
0
0


0.1
0.2
0.2
0.9
0.1
0.1
14.3
0
0
0
0
0
0
0
0
0
----------
----------


130 | 140

0.1 0.1
0.2 0.2
0.2 0.2
0.5 0
0 ...-.---
0 ...
0 ..








---. --- -



.-- - -


150

0.1
0
0












..........:


Oct.
Sept.
Oct.
Sept.
Oct.
Oct.
Dec.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Oct.
Oct.
Oct.
Oct.
Nov.
Oct.
Sept.
Sept.


170 1175

0.1 0



S..~........ ..........


:: ...... : .........
---------- ----------



----------I ----------

----------I ----------



' .. 1 .. .. ..
. -- ----- --I ---.....
---------- ----------





----------I ----------
.......... ..........

--- -- -- ..........


........... ..........
. .......... .........
. .......... ----------.


' ~ ~ '


I








TABLE I.-LONGEVITY OF BOLL WEEVILS PLACED IN A CONSTANT TEMPERATURE INCUBATOR MAINTAINED AT 470F.
(Continued)


Date placed in hibernation


2....................................
20..............................-.. .
22................... ............
27.....- -.........................
19.............................
14................. .............
27 ...................................
29..............................
1................. .... .......
2 .....-----------.............................
30............ .......... ........
27...................................
26................................
30...............................
24 1 ............ .-...-- .........
26...................................
16 ................. ...-...........
15.................... _............
17 ....................................
8...................................
18.................. .............
26................................
4............ _.................


Number
weevils
used


195
510
441
159
647
375
434
890
2227
309
17
641
100
120
100
413
100
340
574
136
70
10
17


Percent weevils


15 1 50 1


..........


63.5

28.3




87.0
93.3
61.0
32.3
51.0
65.6


75 90

1.5 1.0
1.0 0.6
4.3 0.5
3.8 0.6
0.6 0.2
5.8 0.3
0.9 0.5
0.5 0.5
0.4 0.4
1.3 1.3
5.9 0
0.2 0
4.0 0
1.7 0
1.0 0
0.5 0
1.0 0
0 ..
0 ..-
0 ..........
0 ........
0---
.. .... ......---
!


.-ving at specified number of days


S1


Days
10 1120


150 1170 1175

.......... -..........I .........

.........- ........... .........
.......... .......- ...-.......
.......... .......... .........

~......~... .......~....I ..........
..................- .........-

.......... .......... i ..........
.......... .......... I ..........
.......~.. ........... ..........
----.....-...... I....-......



-......-.......... -.... ......
......... --.......... -........
.......... ..........I ..........
................ :::::I .........
..........- .......... .........-
. .......... ....
. .......... ....

I


Sept.
Oct.
Oct.
Oct.
Oct.
Oct.
Sept.
Sept.
Oct.
Oct.
Oct.
Aug.
Nov.
Nov.
Nov.
Aug.
Nov.
Nov.
Sept.
Nov.
Nov.
Oct.
Oct.






Florida Agricultural Experiment Station


TABLE II.-LONGEVITY OF BOLL WEEVILS PLACED IN A CONSTANT TEM-
PERATURE INCUBATOR MAINTAINED AT 600F.


'E Percent weevils



S40 65 75-
3 ^ 40 65 75


490
137
361
640
321
452
78
336
395
276
671
128
470
369
308


living for number of days specified

Days


5s 95 I 105


Date
placed in
hibernation


TABLE III.-LONGEVITY OF BOLL WEEVILS PLACED IN A CONSTANT TEM-
PERATURE INCUBATOR MAINTAINED AT 600F. FOR TWO DAYS AND THEN
TRANSFERRED TO ONE KEPT AT 470F.



Date Placed
in hibernation Percent weevils living for number of days specified
Days
18 i 29-34 138-45 155-63164-70|83-851100-1011106-107 118-1191 125 1512 1160
Sept. 9 988 ... 39.4 7.0 .8 2.1 1.2 0.7 0. 0.2 0.1 0
Oct. 15.... 283 .. 33.2 22.6 8.1 5.7 2. 0.4 0.4 0.4 0 : 1 ... .......
Oct. 13............ 386 61.7 46.9 35.8 27.2 21.8 4.9 1.3 0.3 0 .................


the longevity of the weevil unfavorably since the less abrupt
change from the field temperature to 600F. with a subsequent
change to 470F. did not increase the longevity of the weevil,
though the initial mortality rate increased with less rapidity
than when the weevils were placed directly in the compartment
kept at 47F.
One thousand weevils were placed in the compartment main-
tained at 810F. After 11 days only 1.1 percent of the weevils
were alive, and at the end of 20 days all of them were dead. These
weevils were active throughout their captivity and since they did
not hibernate and were not supplied with food they died quickly.


125 140 160 169


1.0 0.8 0.4 I 0
2.2 0 --...- ......




.------- -----. --- ........

. .. -- - - - -

-i.. .i ...... ..-- ::-:---
-------- --------| --------
.. ---- -------- -------- ---
.- ........ I


Oct.
Sept.
Sept.
Oct.
Sept.
Oct.
Sept.
Sept.
Oct.
Oct.
Oct.
Oct.
Oct.
Sept.
Sept.


21..-.....
8..........
9.....---.
16..........
15..........
11..........
14..........
5..........
5---
12..........
13......
14. ......-
19.........
15..........
11..........
6.........


1






Bulletin 240, Weevil Hibernation, Controlled Conditions 11

The ability of newly hatched weevils to enter forced hiberna-
tion at a low temperature was determined by placing 2,611 newly
hatched and unfed weevils into the 470F. compartment. Over
60 percent of the weevils lived nine days but a sharp break oc-
curred on the tenth day when all but 25.3 percent had died. Dur-
ing the following three days all but 3.9 percent of the weevils
died and at the end of 60 days the last individual died. In con-
trast with the field-caught weevils kept at 470F. these weevils
lived but a short time, but when compared with the field weevils
kept at 810F., they lived a relatively long time. Table IV pre-
sents the longevity data for newly hatched weevils when kept
in an incubator maintained at 470F.
PERCENT OCTOBER 13,1927
100
80-
60
40
30
20


8




810 E INSECTARY 470FE \ "\60 E 470' TN

0 10 20 30 40 50 60 70 80 90 100 110 120
DAYS.
Fig. 1.-Chart showing the comparative longevity of boll weevils placed
in incubators maintained at 47F., 60F., and 81F., respectively. (Plot-
ted on a semi-logarithmic or ratio scale.)
Boll weevils captured in the field on October 13, 1927, were
divided into groups and placed in the compartments kept at
470F., 600F., and 810F., respectively. One of two groups placed
in the incubator maintained at 60F. was transferred to the
470F. incubator after two days. At this time, in addition to the
2,167 weevils used in the four groups, the 2,611 newly hatched
weevils previously mentioned were placed in the compartment
kept at 470F. A chart showing the relative longevity of the
weevil groups used in this comparative test is presented in Fig.
1. The weevils which were placed in the compartment main-
tained at 81F. died quickly, and, after a 40-day interval, were
followed by the unfed, newly hatched weevils. The mortality






Florida Agricultural Experiment Station


rate of the weevils kept at 60'F. did not lag far behind, but the
two groups of weevils placed in the compartment kept at 470F.
lived considerably longer than any other group. Though the
initial mortality rate of the weevils placed in the 470F. incubator
was higher than that of the weevils placed in the 60'F. com-
partment, the subsequent mortality rate was lower.
TABLE IV.-LONGEVITY OF NEWLY HATCHED BOLL WEEVILS PLACED IN
A CONSTANT TEMPERATURE INCUBATOR MAINTAINED AT 470F.
Number Percent weevils living for number of days specified
weevils Days
used 3 6 9 10 13 30 40 53 60

2,611 97.6 79.6 63.7 25.3 3.9 1.3 0.7 0.5 1 0


At the conclusion of these tests it was noted that the longest-
lived weevil died at the end of 170 days, whereas individual
weevils confined in hibernation cages on the ground in the woods
lived as long as 257 days (1) and weevils entering cotton fields
in May and June lived at least from 180 to 210 days (3). Sev-
eral conditions under which the weevils were kept in the incu-
bators, however, differed from those under which the weevils
lived in the hibernation cages or in the woods. In the first place,
the incubators were maintained at a constant temperature and
the weevils were therefore kept in complete hibernation, while
the weevils either in cages or in fields in Florida were subjected
to temperature fluctuations and undoubtedly emerged from and
reentered hibernation. Secondly, the weevils in the incubators
were subjected to constant relative humidity, whereas in the field
or in the hibernation cages they were exposed to a wide range
of relative humidities. Thirdly, the weevils in the incubator
were not covered with Spanish moss, leaves or other hibernating
material, while both the field cages and the natural hibernating
quarters offered abundant material for insulation. Changes in
either temperature or humidity were not considered advisable,
since the optimum temperature and humidity conditions for hi-
bernation in the incubators had been determined. A change in
the immediate environment of the weevil, however, was con-
sidered and another series of tests was planned in which Spanish
moss was selected for partially filling each of the small screen
cages used for confining the various groups of weevils kept in
the incubator.







Bulletin 240, Weevil Hibernation, Controlled Conditions 13

EXPERIMENTAL DATA, 1928-29

The experiments conducted during 1928-29 included tests in
which the weevils were kept at 470F. The relative humidity was
maintained between 79 percent and 85 percent. The immediate
environment of the weevils, however, was changed, since each
screen cage was supplied with sufficient Spanish moss to afford
insulating material similar to that in which the weevil naturally
hibernates.
Beginning on October 12 and continuing until November 16,
1928, 26 groups of weevils were captured and placed in the in-
cubator. A total of 53,484 weevils was used: 21,589 of this
number were captured near Omega, Georgia, and the remainder
were collected in a large field near Gainesville, Florida.

TABLE V.-LONGEVITY OF BOLL WEEVILS PLACED IN ARTIFICIAL HIBERNA-
TION QUARTERS MAINTAINED AT 470F. AND 80 TO 90 PERCENT RELATIVE
HUMIDITY, 1928-29.


Date Number
placed in weevils
hibernation used

Oct. 15...... 702
12.... 992
20- .. 971
24 ..... 3800
22**.... 3000
17........ 1080
19........ 1040
16 ..... 1020
18........ 1018
Nov. 9........ 3613
13........ 3013
15........ 3059
14........ 2999
12.......- 1442
Oct. 31* .... 1595
Nov. 16 ...... 2103
10*..... 3188
5.. .... 2043
8*..... 2342
3*...... 1007
14* ...... 1300
15*...... 2725
2*...... 3950
12*...... 861
9*...... 1695
16*..... 2926


Percent weevils living for number of days specified
Days
35 | 70 | 170 | 225 | 300 330 1 350 | 359 |1 362

56.0 28.5 19.1 12.8 ...... 0.5 0.3 0.1 [ 0
50.0 43.7 33.1 24.0 ........ 0.4 0.1 0 ........
54.2 48.5 32.7 24.1 0.9 0.3 0 ........ ...
57.5 50.8 34.0 27.3 1.6 0.1 0 .......I .....
58.7 49.4 33.5 23.3 .. ... ... ......
36.5 29.3 19.7 14.4 0.6 0.2 0 .... ......-
35.4 25.7 16.4 10.7 0.6 0 ....... ....... .-.-.
35.3 29.2 19.6 13.9 0.9 0 ....... ....I.......
33.2 26.5 14.1 9.0 0.2 0 -.............. ........
40.5 28.5 6.4 3.7 0.1 0 I ..... ... .......
49.8 36.0 16.7 7.9 0.1 0 ..... .... .... ..-
44.7 28.4 11.7 5.9 0.1 0 -.... ..............
47.1 29.1 8.3 3.2 0.1 0 ...- .. ........ .....
40.6 30.9 11.9 6.7 0 ........ ..... ........ .......
34.2 22.2 11.9 6.4 0 .........-... ....I ....
49.6 32.6 4.9 3.6 0 ... .. ........ ---- ..-----
14.0 ...-..... 6.8 3.9 0 ..... ............ .....
50.2 ....... 3.6 1.7 0 --.. .......... I ...
11.8 6.7 1.1 0.3 0 ....... ........ ..... .....
16.4 .......... 0.1 0.1 0 ...... ...- ......
17.7 8.5 0.4 0.2 0 ....... ....... ......
24.0 10.0 0.3 0.1 0 -..... ............ ...
28.5 12.9 0.18 0 ....... ...- ...... .. .....
19.9 10.9 0.8 0 ....... ............ .... .....
14.0 7.9 0.02 0 ....... .............. ..... ... ......
16.9 5.7 0.03 0 -.. .... ..... ........ I ..... -... .


*Weevils shipped from Georgia.
**Weevils used for other experimental work.







Florida Agricultural Experiment Station


PERCENT u.I.uLN is
,^0 -


Fig. 2.-Chart showing semi-logarithmic graphs of the mortality rate of
individual groups of boll weevils placed in artificial hibernation, 1928-
29.





Bulletin 240, Weevil Hibernation, Controlled Conditions 15

The dead weevils were removed from the cages and recorded
twice a month during the first six months. After that time
more frequent counts were made possible by the greatly reduced
number of weevils which remained in the incubator. The dates
on which the weevils were placed in the incubator, the number
of weevils used, and the percent living at the end of specified
periods of time are presented in Table V.
As a consequence of the change in the immediate environment
of the weevil by the addition of Spanish moss to the cages, the
longevity of individual weevils was increased from 170 days
without the Spanish moss to 359 days with the moss. Where
the weevils were insulated with moss, as high as 34 percent in
one of the groups of 3,800 weevils were alive at the end of 170
days, the length of time during which all of the 50,000 weevils
previously placed in the incubator without Spanish moss had
died.
Figures 2, 3, and 4 present semi-logarithmic graphs of the in-
dividual groups of weevils in this series. Each graph shows the
comparative rate, in percent, of the number of weevils dead at
any time. The semi-logarithmic graph is used in order to pre-
sent the data with reference to the percent of the weevils dying
relative to the number living at any specified time.
The graphs of the groups which contained the longest-lived
weevils show a high mortality rate during the first month spent
in hibernation. This high mortality rate is followed by a com-
paratively low rate for the ensuing seven months, and then an
abrupt increase in the mortality rate reappears. Graphs of the
individual groups are arranged in order according to the length
of the period during which there is a low mortality rate.
Contrary to the data which were obtained in the 1927-28 se-
ries, there is an apparent better fitness for hibernation in the
weevils captured during the latter part of October rather than
during the entire period of collections. All of the groups placed
in the incubator during October appear in Fig. 2 (the longest-
lived groups) with the exception of one October group of weevils
which were collected in Georgia. The groups in which the
weevils were not so long-lived showed still sharper initial rates
of mortality, followed by shorter periods of reduced mortality
rates and more abrupt second periods of increased mortality
rates. Finally, the groups of short-lived weevils showed no ex-
tended periods of reduced mortality rate.







Florida Agricultural Experiment Station


Fig. 3.-Chart showing semi-logarithmic graphs of the mortality rate of
individual groups of boll weevils placed in artificial hibernation, 1928-
29.


------------- 41
--^-----
u
s~
K

'I
--
-- ----
------------ 1
--- --- --
n


~I






Bulletin 240, Weevil Hibernation, Controlled Conditions 17


Fig- 4.-Chart showing semi-logarithmic graphs of the mortality rate of
individual groups of boll weevils placed in artificial hibernation, 1928-
29.
The weevils captured near Omega, Georgia, inhabited cotton
fields in which the plants showed a marked determinate growth.
As a consequence, they were not so well fed on green foliage
and squares as were the weevils captured near Gainesville, Flor-
ida. It is quite possible that the transportation of the weevils
from Georgia to Florida also decreased the vigor of the weevils
.somewhat. There is a strong indication nevertheless, that poor
feeding conditions in the Georgia fields caused the marked re-
duction in longevity which was in evidence among the weevils
from Georgia.
In this connection the process of destroying the cotton stalks
as soon as possible after the crop has been picked may be ad-
vertently advised. Though some of the graphs of the various
groups of weevils might indicate that stalk destruction could
not be profitably carried out, nevertheless, early destruction of
the stalks would, in all probability, place the weevils in the po-





Florida Agricultural Experiment Station


sition of the ones which were pictured in Figs. 3 and 4. The re-
moval of the food supply, such as occurred with the weevils from
Georgia, forces the weevil to enter hibernation under conditions
far less favorable than when an abundance of food is available
for rearing well-fed individuals. Consequently, they are ill-fitted
for withstanding an extended period of hibernation.
The series of tests conducted during 1928-29 showed conclu-
sively what length of time the boll weevil could successfully live
in artificial hibernation quarters. These data, when combined
with hibernation cage data, indicate the possibility of a pro-
longed period during which the hibernated boll weevil can enter
and infest a cotton field.
Assuming that boll weevils leave the cotton fields and enter
hibernation on November 1, December 1, or January 1, and re-
enter the fields on June 15, a period of 236 days, 206 days, or
175 days, respectively, would have been spent by the weevils in
hibernation. The experimental data secured from the 1928-29
tests show that at the end of 170 days approximately 20 percent
of the 32,000 Florida weevils placed in hibernation were living;
the lapse of 206 days found approximately 15 percent still alive;
and 236 days passed with about 10 percent of the total number
of weevils which had been placed in complete hibernation still
living. Approximately 0.6 percent of the 32,000 weevils lived
300 days, indicating that when the hibernation conditions are
favorable, one weevil out of each 200 to enter hibernation on
October 1 could live long enough, all other hazards being elim-
inated, to emerge from hibernation on August 1, of the follow-
ing year; or entering on November 1, could emerge on September
1. It is also a significant fact that one of the weevils caught in
the field, and used for these tests, besides the time spent in the
cotton field, lived for an additional 359 days in complete hiberna-
tion. Though the majority of the weevils found to invade a
cotton field soon after quitting hibernation were located during
June, it is quite possible that individual weevils may remain in
hibernation in the woods until late in July or August. As a
matter of fact one weevil emerged from hibernation in a cage on
September 7, having spent at least 308 days in the cage without
food, and at least 191 days of this time in complete hibernation
(3). The hibernation cage was located on the ground in the
woods and the weevil had been exposed to the natural changes in
temperature and humidity during this time.





Bulletin 240, Weevil Hibernation, Controlled Conditions 19

CONCLUSIONS

Approximately 125,000 weevils were used in experiments con-
ducted in controlled temperature incubators maintained at 470F.,
600F., and 810F. and between 79 and 85 percent relative hu-
midity. An individual weevil lived for 359 days in artificial hi-
bernation quarters maintained at 470F. At the end of 170 days,
20 percent of 32,000 weevils were living; 206 days, 15 percent;
and 236 days, 10 percent. From these data it can be assumed
that in Florida, all other hazards than those affected by tem-
perature and humidity being eliminated, 10 percent of the
weevils entering hibernation on November 1 could survive until
June 24; 15 percent of those entering on December 1; and 20
percent of those entering on January 1 could live until the same
date.
Results obtained with weevils placed in the incubators main-
tained at 470F. indicated that there were two periods of in-
creased mortality rates, the first occurring during the first
month of dormancy and the second following a period of several
months of low mortality rate. The extended period of low mor-
tality rate is apparently dependent on the conditions of the
weevil at the time it enters hibernation; well-fed weevils being
long-lived, poorly-fed weevils being short-lived.
The destruction of the cotton stalks as soon as possible after
the crop has been picked not only removes the breeding quarters
of the boll weevils, thereby reducing the number of weevils
which can prepare themselves for hibernation, but also prevents
the weevils already in the field from feeding adequately for
withstanding an extended period of hibernation.

LITERATURE CITED
1. GROSSMAN, EDGAR F. Longevity records of the cotton boll weevil.
The Fla. Entomologist 12:57-59. 1928.
2. .......................... Some humidity and temperature effects on the
development and longevity of the boll weevil. The Fla. Entomolo-
gist 14:66-71. 1930.
3. GROSSMAN, EDGAR F., and P. W. CALHOUN. Determination of the
winter survival of the cotton boll weevil by field counts. Fla. Agr.
Expt. Sta. Bul. 233:1-47. 1931.
4. HINDS, W. E., and W. W. YOTHERS. Hibernation of the Mexican
cotton boll weevil. U. S. Dept. Agr. Bur. Ent. Bul. 77:1-106. 1909.
5. NEWELL, WILMON, and M. S. DOUGHERTY. The hibernation of the cotton
boll weevil in Central Louisiana. State Crop Pest Comm. La. Circ.
31:163-219. 1909.





Bulletin 240, Weevil Hibernation, Controlled Conditions 19

CONCLUSIONS

Approximately 125,000 weevils were used in experiments con-
ducted in controlled temperature incubators maintained at 470F.,
600F., and 810F. and between 79 and 85 percent relative hu-
midity. An individual weevil lived for 359 days in artificial hi-
bernation quarters maintained at 470F. At the end of 170 days,
20 percent of 32,000 weevils were living; 206 days, 15 percent;
and 236 days, 10 percent. From these data it can be assumed
that in Florida, all other hazards than those affected by tem-
perature and humidity being eliminated, 10 percent of the
weevils entering hibernation on November 1 could survive until
June 24; 15 percent of those entering on December 1; and 20
percent of those entering on January 1 could live until the same
date.
Results obtained with weevils placed in the incubators main-
tained at 470F. indicated that there were two periods of in-
creased mortality rates, the first occurring during the first
month of dormancy and the second following a period of several
months of low mortality rate. The extended period of low mor-
tality rate is apparently dependent on the conditions of the
weevil at the time it enters hibernation; well-fed weevils being
long-lived, poorly-fed weevils being short-lived.
The destruction of the cotton stalks as soon as possible after
the crop has been picked not only removes the breeding quarters
of the boll weevils, thereby reducing the number of weevils
which can prepare themselves for hibernation, but also prevents
the weevils already in the field from feeding adequately for
withstanding an extended period of hibernation.

LITERATURE CITED
1. GROSSMAN, EDGAR F. Longevity records of the cotton boll weevil.
The Fla. Entomologist 12:57-59. 1928.
2. .......................... Some humidity and temperature effects on the
development and longevity of the boll weevil. The Fla. Entomolo-
gist 14:66-71. 1930.
3. GROSSMAN, EDGAR F., and P. W. CALHOUN. Determination of the
winter survival of the cotton boll weevil by field counts. Fla. Agr.
Expt. Sta. Bul. 233:1-47. 1931.
4. HINDS, W. E., and W. W. YOTHERS. Hibernation of the Mexican
cotton boll weevil. U. S. Dept. Agr. Bur. Ent. Bul. 77:1-106. 1909.
5. NEWELL, WILMON, and M. S. DOUGHERTY. The hibernation of the cotton
boll weevil in Central Louisiana. State Crop Pest Comm. La. Circ.
31:163-219. 1909.







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