45

Book C 2; pa ;

an

au

“
.

U.S. DEPARTMENT OF AGRICULTURE,

BUREAU OF ENTOMOLOGY—BULLETIN No. 100.
L. O. HOWARD, Entomologist and Chief of Bureau.

THE INSECT ENEMIES OF THE
COTTON BOLL WEEVIL

BY

W. DWIGHT PIERCE,
Agent and Expert,

ASSISTED BY
R. A. CUSHMAN anv C. E. HOOD,
Agents and Experts,
UNDER THE DIRECTION OF

W. D, HUNTER,

Agent and Expert,
In Charge of Southern Field Crop Insect Investigations.

IssuED APRIL 3, 1912.

WASHINGTON:

GOVERNMENT PRINTING OFFIOE,
1912,

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF ENTOMOLOGY—BULLETIN No. 100.
L. O. HOWARD, Entomologist and Chief of Bureau.

THE INSECT ENEMIES OF THE
COTTON BOLL WEEVIL. |,

BY

W. DWIGHT PIERCE,
Agent and Expert,

ASSISTED BY

R. A. CUSHMAN anp C. E. HOOD,
Agents and Experts,

UNDER THE DIRECTION OF
W. D, HUNTER,
Agent and Expert,
In Charge of Southern Field Crop Insect Investigations.

Issurp Apri. 3, 1912.

WASHINGTON:

GOVERNMENT PRINTING OFFIOE,
1912,

BUREAU OF ENTOMOLOGY.

L. O. Howarp, Entomologist and Chief of Bureau.
©. L. Martatr, Entomologist and Acting Chief in Absence of Chief.
R. 8S. Curron, Executive Assistant.
W. F. Tastet, Chief Clerk.

F. H. CurrrenvEN, in charge of truck crop and stored product insect investigations.
A. D. Hopkins, in charge of forest insect investigations.

W. D. Hunter, in charge of southern field crop insect investigations.

F. M. WessTER, in charge of cereal and forage insect investigations.

A. L. QUAINTANCE, in charge of deciduous fruit insect investigations.

E. F. Parues, in charge of bee culture.

D. M. Rogers, 771 charge of preventing spread of moths, field work.

Rouia P. Currie, in charge of editorial work.

MABEL Co.tcorp, in charge of library.

SOUTHERN FieLtp Crop INSEcT INVESTIGATIONS.

W. D. Hunter, in charge.

W. D. Pierce, J. D. Mrrcnett, G. D. Smit, E. A. McGrecor, Harry PInKus,
W. A. THomas, D. C. Parman, B. R. Coan, engaged in cotton boll weevil inves-
tigations.

F. C. BrsHopp, A. H. Jennincs, H. P. Woop, W. V. Kine, G. N. Wotcort, a
in tick life-history investigations.

A. C. Morean, G. A. Runner, 8. E. Crump, engaged in tobacco insect investigations.

J. L. Wess, T. E. Hotnoway, E. R. Barser, engaged in sugar cane and rice insect
investigations.

R. A. Cootzy, D. L. Van Dine, Witmon NEWELL, A. F. Conrant, C. C. KRUMBHAAR,
collaborators.

2

LETTER OF TRANSMITTAL.

U. S. DEPARTMENT OF AGRICULTURE,
Bureau OF ENTOMOLOGY,
Washington, D. C., September 28, 1911.

Str: I have the honor to transmit herewith a manuscript entitled
““The Insect Enemies of the Cotton Boll Weevil,” by Messrs. W.
Dwight Pierce, R. A. Cushman, and C. E. Hood, agents and experts
engaged in cotton boll weevil investigations. The present manu-
script contains a complete summary of the studies of the boll-weevil
parasites conducted since 1905. The boll weevil is now known to
be attacked by 29 species of parasites and 26 species of predatory
insects, most of which are indigenous to the United States. It is the
purpose of this manuscript to show the sources and value of these
enemies and to indicate how they may be utilized to the advantage of
the farmers of the cotton belt. I recommend the publication of this

manuscript as Bulletin No. 100 of the Bureau of Entomology.

Respectfully,
L. O. Howarp,
Entomologist and Chief of Bureau.
Hon. JAMES WILSON,
Secretary of Agriculture.

CONTENTS.

MIPOCUGIION 22) a osa eo eae were aoa kee oe ee ee Sweet cs a He 32s
Conducwor te PATASILS. PTOJECt...csedsc ovens hee en cece eee esse et jee e
Stree tee Sees be Mok arts ata a ac ala ae opt ae ee Se eee S
Seopa Ob present LepONasc <iocas Seis ae etcetera sas oe em So nmin

Part I.

on o

=
ow

Ie

Part Ll.
. A list of the insect sane of ae eottom boll weevilss:.-.....sse.a222

eH

os bo

a
wNOorowWOON DO

|

16.

The status of the cotton boll weevil and its enemies.

. A general chronological study of the insect control of the boll weevil. .
. Nature and sources of the material examined..............-...-------
. Seasonal studies of insect control, by class of infested material......--
. A geographic study of the statistics of insect control.........-.-..----
. A study of the share of insect control in the mortality of immature boll

SEES CaCl ye mae, SU eae SN ee eng gr ce ele gin yo me Se te

. A study of how agriculture modifies insect control..............-..----
Beer ie MICE WOMAe eee anee wcg ot Bei Sarat eo: Soc ees
. How insect control follows the dispersion of the boll weevil........-.--
. The status of the boll weevil and its control by insects............-...
. A brief statement of the various classes of control exercised upon the

jaya arate ver tr | eeegenee me ctgpeets Nat ok RR een a em NCR SRN ok gE me On oS
Practical conclusions derived from statistical studies..............-.--
Biological complex.

. Flies sen anamibibe the boll ee yo Sane

. The hymenopterous parasites of the aie weev il. eee ee eae
. Biological notes upon the parasites of the weevil .............-.------
| Phe deyclopmrinn Of the pardsltes se sceccta nao Soc cee ewes. Shee
o hhe distripinuon or OC DArasibes. Fae iciad so oS ads odslnae dn dean o's
PU oii ate ACHR See asad Seen eee Meh ee oa ees dos hes ieee «
Meech ieisincstesaqeg fake tt ch gh <) | eneeeneeer aa oO ee oe ee ee ae
. Beetles which prey upon the boll weevil.....................-------
: Lepidopterous larve which are incidentally predatory upon the boll

SAnisewnien prey upon the Doll weevil j.occacees ose aene ee sec ewe geen
4. Biology of the cohosts of the boll-weevil parasites............-...----
. A list of the host plants of the cohost weevils.........-...-.....-....-

Asummary of the more important biological facts Ee ee eee

Part III. The economic application.

ai

“Im OF ® CO LO

8.

Phecconenuce pritciples wivolved 2.23: 2. s.ete dee case Soke 5) we

~ Interpretation Of parasite Sta lishiCe..ss- soso. cnt ees Peed Se Ju eee .n
= interpretation of the: brolvsical complex. ).62 cose ve ecu ne oa ns ne
eHow t6-pron. by existe CONGIUONS ocak 2c osha od sce wees Sh aes Sx
. How to plan for the greatest possible control.........---......-------
,~Propaeation and artiicial imtroductions .°.2..2--.2-2- sees... ic een
‘ Objectionable DIACHICOS regan sew esc

The economic apnaneatioe ‘of the ivesueatiotic.

ESOS eM Yad 22-32 Se MGS Se diennys oureic Sa arsnars wearers Sree) vane 'dymiig wie Se gl een ce

66
68

LLU SJ Rea Nes.

PLATES.

Puate [. Shedding and retention of forms on the cotton plant. Fig. 1.—Normal
scars left by shed forms. Fig. 2.—Abnormal scars with forms
retained. Fig. 3.—Longitudinal section through base of retained
OUD on. Eph ae epee Selatan ee

II. Eggs of boll-weevil parasites. Fig. 1.— Microdontomerus anthonomi.
Fig. 2.—Unidentified egg. Fig. 3.—Cerambycobius cyaniceps.
Fig. 4.—Eurytoma tylodermatis. Fig. 5.—Catolaccus hunteri. Fig.
6i— Wind entiticdsect 1. sues hoe see uss eos eee ee
III. Parasites of weevils. Fig. 1.—Eurytoma tylodermatis, pupa. Fig. 2.—
Catolaccus incertus, pupa. Fig. 3.—Cerambycobius cyaniceps, pupa.
Fig. 4.—Microdontomerus anthonomi, pupa. Fig. 5.—Larva of
Microbracon. Fig. 6.—Microbracon mellitor, pupa. Fig. 7.—Larva
SiGha ldo cnet. hos oe, aoe eee eee ee

TEXT FIGURES.

Fie. 1. Diagram illustrating the monthly percentage of mortality of immature
boll weevils due to insect enemies..................2-.-2----+---

2. Diagram illustrating the average climatic and insect control of the

immature boll weevils during 1906, 1907, 1908, and 1909, in hanging
BOWE CR cece ciara ethaie esa ae cans Sind ate eee eee ei

3. Diagram illustrating the average climatic and insect control of the

immature boll weevils during 1906, 1907, 1908, and 1909, in fallen
ROUUTCH Suche om es Se Sar ee ae oe eee ee ee

4. Diagram illustrating Texas climatic variations in 1907, 1908, and 1909.

5. Diagram illustrating Louisiana climatic variations in 1907, 1908, and
RGD soe, Sis Stature piranha cat les pe ae rec teeta

6. Diagram illustrating the boll-weevil complex ...............-.--+----
7. Diagram giving the parasites of the boll weevil and their other hosts.

8. Pediculoides ventricosus: Adult female, before and after inflation of
abdomen with eggs and young....................---------e+e--

9.. Microdontomerus uninonomis AGUL scone tee 0 os oon Saee eee e
LO, eabrocyyis pier cer PV WOc-<0.cec.carctae sgieel ewes st ae ae
11. Sigalphus curculionis: Male, female, antenna................-----.--

12. Mrerobrocon metitom: Adult ves. el. ee eee en een en nea ee
13. Diagram illustrating yearly rank of the boll-weevil parasites, 1906,
1907, LA08 end G09: See os Sag once eae. ae ee

14. Map showing the distribution of the more important parasites of the
boll weevils. = 4 s¥s5 Jen. ae tase eee ees eee eee ae ee
15. Diagram illustrating the seasonal rotation of hosts of Catolaccus huntert
and Cerambycobius cyaniceps .......2.....22-00e eee e eee ence eee
16. The ‘‘fire ant’ (Solenopsis geminata): Worker............----------
17. The little black ant (Monomorium minimum): Adult, egg, larva, pupa -

56

56

19

Fia. 18.
19.
20.
PAL
22.
20.
24.
25.
26.

INSECT ENEMIES OF THE BOLL WEEVIL.

The little red ant (Monomoriwm pharaonis): Female and worker. ....
The coffee-bean weevil (Aracerus fasciculatus): Adult, larva, pupa. ..
The bloodweed weevil (Lirus scrobicollis): Adult. .................-
The ironweed weevil (Desmoris scapalis): Adult..................---
The pepper weevil (Anthonomus eugenii): Adult. ................--
The cowpea weevil (Chalcodermus xneus): Adult... ............-..--
The plum curculio (Conotrachelus nenuphar): Larva, adult, pupa.....
The potato-stalk weevil (Trichobaris trinotata): Adult, larvee, pupe..
The rice weevil (Calandra oryza): Adult...............--00ce-ee eee

~I

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Coons ow

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THE INSECT ENEMIES OF THE
COTTON BOLL WEEVIL.

INTRODUCTION.

When the cotton boll weevil first entered the United States it
appeared to have almost undisputed sway. It did, in fact, escape
most of its enemies. But whether parasites were introduced with it
or not, we now know that within the first three years of its existence in
Texas it was attacked by three important species of parasites. Year
after year new factors in its control are becoming apparent, although
some have probably been concerned since the beginning. On the other
hand, it is certain that entirely new elements are entering the struggle
as rapidly as the weevil enters new biological complexes. Among the
most striking of these new elements in the control is the recent adjust-
ment of Microdontomerus anthonomi Crawford (fig. 9, p. 49). This spe-
cies was unknown until 1906 when a very few were taken in material
reared at Cuero, Goliad, Hallettsville, Victoria, and Waco, Tex.
In 1907 it was found to predominate in a portion of central Texas.
In 1908 its range was found to extend northward to the Red River.
In 1909 it was found as far east as the Mississippi River in Louisiana.
Only a single record of the occurrence of Sigalphus curculionis Fitch
(fig. 11, p. 53), the common parasite of the plum curculio, had been
made prior to 1908. In that year it began to make its presence felt
in northeastern Louisiana and western Mississippi. In 1908 a new
chalcidoid parasite, recently described as Tetrastichus huntert Crawford,
was found to be the leading parasite of the boll weevil in northern
Louisiana and western Mississippi. In 1909 this species was found
as far west as Arlington, Tex.

With the advent of each new enemy and its more complete adjust-
ment, the power for damage possessed by the weevil is by so much
diminished. On the other hand, every factor which checks these
enemies without also checking the weevil benefits the weevil.

If the solution of the boll-weevil problem consisted merely in adding,
one by one, factors which would cut off a given percentage of the
weevils, the time would not be distant when that might be accom-
plished. The problem is far more complicated. The various factors
do not discriminate against one another, for while heat, ants, cold
weather, and excessive moisture may remove many parasites from
the struggle, it also follows that heat, cold weather, heavy rains,

9

10 INSECT ENEMIES OF THE BOLL WEEVIL.

predators, and other pests remove many ants. Proliferated plant
tissue frequently acts as an important check upon the weevil, and yet
in many cases it serves as a food for the weevil rather than as a con-
trolling force. Moist weather aids the weevil. The leaf-worm, while
cutting off most of the weevil food, finally is checked by parasites.
Light, heat, and dryness favor certain parasites, whereas shade and
moisture favor others. Parasites that are normally primary fre-
quently waste their energies by accidentally becoming secondary,
and normally secondary parasites, and probably tertiary as well, also
enter the consideration. Predatory enemies fail to distinguish the
parasites from the weevils, but are in turn held in check by their own
enemies. The birds devour weevils, predators, and parasites, but
they in turn are kept down by other birds and even man himself,
and thus the complexity grows.

There are 49 species of insects which attack the immature stages of
the boll weevil. Of these insects 29 species may be classed as para-
sitic, 5 as predatory larvee, and 15 as predatory adults. They are
divided among the orders, with 3 in the Acarina, 4 in Coleoptera, 36
in Hymenoptera, 5 in Diptera, and 1 in Lepidoptera. One of the
acarians, 1 coleopteron, 15 Hymenoptera, and 1 dipteron, may be
considered as quite important. A weighted average mortality of
3.93 per cent of all immature stages may be accredited to the com-
bined factors of all parasitic enemies; the predators are responsible
for 15.93 per cent, while climate is responsible for 24.45 per cent, and
plant proliferation 12.42 per cent. This makes the total natural
control of immature stages 56.73 per cent.

In addition to the insects attacking the boll weevils in the squares,
there must be considered the insects which prey on the adults. These
include one praying mantis, one predaceous bug, two beetles, and
two ants—six species in all.

This bulletin is not concerned with the mortality of the weevils
after they become adult because reliable figures can not be gathered
upon this point. It is certain that many weevils fall prey to preda-
ceous insects and to birds, and the well-known habits of the horned
lizard would include it in the list of possible enemies. The important
fact is that 56 per cent of the weevil eggs fail to produce adult weevils.
The remainder is still a formidable number but the many adverse
influences continue to operate upon the adults and likewise upon
their progeny.

CONDUCT OF THE PARASITE PROJECT.
The investigation of the insect enemies of the cotton boll weevil

was initiated in 1905. It has been conducted from the beginning by
the senior author under the direction of Mr. W. D. Hunter, and with

HISTORICAL DATA. it

the direct influence and encouragement of Dr. L. O. Howard, Chief
of the Bureau of Entomology. Messrs. R. A. Cushman and C. E.
Hood have been intimately associated in the preparation of the
material for this bulletin since 1907. The collecting, examining, and
recording of the immense mass of material has involved in addition
the services of Messrs, E. A. Schwarz, J. D. Mitchell, W. E. Hinds,
Wilmon Newell, F. C. Bishopp, A. C. Morgan, F. C. Pratt, C. R.
Jones, W. W. Yothers, G.D.Smith, A. H. Rosenfeld, H.S. Smith, E.S.
Tucker, T.C. Barber, 8. Goes, C.S. Spooner, C. W. Flynn, T.C. Paulsen,
J. A. Hyslop, V. I. Safro, T. E. Holloway, H. Pinkus, W. H. Hoffman,
¥. L. Elliott, and O. M. Lander. Considerable credit is due Messrs.
EK. A. Schwarz, J. C. Crawford, W. M. Wheeler, D. W. Coquillett, and
C. H. T. Townsend for determination of the insects concerned. The
weevils entering the biological complex have been determined by the
senior author. In short, 33 entomologists have directly contributed
the data which are herewith presented.

HISTORICAL DATA.

The first definite records of the parasites of the cotton boll weevil
were made by C. H. T. Townsend in 1895 when he mentioned a small
hymenopterous parasite and also recorded the suspicious occurrence
of several species of Scymnus in the squares, and mentioned that a
fungoid parasite, a species of Cordyceps, ‘‘was found growing out of a
dead pupa in its cell in a boll, November 26, in a field in San Juan
Allende, Mexico.’’ (Townsend, 1895.) In 1901 Profs. Herrera and
Rangel published notes concerning the parasitic attack of Pedi-
culoides ventricosus Newport (fig. 8, p. 46) upon the boll weevil
(Rangel, 1901b, 1901e).

In 1902 Dr. Wm. H. Ashmead described Bruchophagus herrere from
Coahuila, Mex., as a primary parasite of the boll weevil (Ashmead,
1902a, 1902b; Herrera, 1902a). This is probably Furytoma tylodermatis
Ashmead. Prof. Herrera also recorded the activities of a predaceous
ant, Mormica fusca Linn., subspecies subpolita Mayr, variety perpilosa
Wheeler, (Herrera, 1902b; Wheeler, 1902). In the same year Prof.
F. W. Mally recorded the fact that Bracon (now Microbracon) mellitor
Say (fig. 12, p.54) and Hupelmus (now Cerambycobius) cyaniceps Ash-
mead had been reared by him, since 1899, in considerable numbers
from the boll weevil. He also recorded a species of Hurytoma.
(Mally, 1902.)

In 1904 Hunter and Hinds recorded additional primary parasites
as follows: Sigalphus curculions Fitch (fig. 11, p. 53), Catolaccus
incertus Ashmead, Urosigalphus (robustus Ashmead), Bracon (dorsator
Say), and Hurytoma tylodermatis Ashmead, as well as an entomog-
enous fungus, Aspergillus (Hunter and Hinds, 1904). The Urosi-

12 INSECT ENEMIES OF THE BOLL WEEVIL.

galphus has since heen described as Urosigalphus anthonomi Crawford
(Crawford, 1907a).

In 1906 Mr. Nathan Banks described a mite, T’yroglyphus breviceps,
collected at Victoria, Tex., from boll-weevil larve (Banks, 1906).

In 1907 the senior author of this bulletin added Hydnocera pubescens
LeConte as a predaceous enemy of the boll weevil (Pierce, 1907a, 1907b,
1907c). In the same year Dr. Hinds published two papers in which
the work of Solenopsis geminata Fab. (fig. 16, p. 70), variety xyloni
McCook, as a predator on the boll weevil was fully discussed, and
considerable statistical data on the parasitic control of the weevil
were presented (Hinds, 1907a, 1907b). Mr. Morgan published a
brief account of the predatory attack of a bug, Apiomerus spissipes
Say (Morgan, 1907). Mr. J. C. Crawford described as parasites of
the boll weevil Torymus anthonomi, Urosigalphus anthonomi, and
Urosigalphus schwarz (Crawford, 1907a).

In 1908 the senior author of this report recorded Catolaccus antho-
nomi Ashmead as a boll-weevil parasite and Cathartus cassie Reiche
(gemellatus Duval) as a predator (Pierce, 1908a, 1908b, 1908c, 1908d).
Mr. Crawford described Cerambycobius cushmani and Catolaccus
hunteri as new parasites of the boll weevil (Crawford, 1908). During
the same year two new predaceous enemies of the boll weevil were
recorded from Louisiana, namely, Evarthrus sodalis LeConte and
Evarthrus sp. (Newell and Trehearne, 1908). Mr. Townsend, in a
paper on the muscoidean flies, recorded Ennyomma globosa 'Townsend
as a parasite of the boll weevil (Townsend, 1908). During 1909 Mr.
Crawford described Tetrastichus hunteri as a parasite of the boll weevil
(Crawford, 1909b).

SCOPE OF PRESENT REPORT.

The present report is supplementary to a former bulletin which
was based on investigations prior to 1907 (Pierce, 1908a). The
matter contained herein has mainly been gathered during the years
1907, 1908, and 1909. Only such notes as are of value for the sake of
comparison have been repeated from the previous report.

The work is divided into three parts:

I. The status of the cotton boll weevil and its enemies.

II. The biological complex.

Ill. The economic application.

PART I. THE STATUS OF THE COTTON BOLL WEEVIL AND ITS
ENEMIES.

Part I of this bulletin shows the large mass of statistical material
gathered during the four years of the parasite investigation, and |
attempts to place this material in such form as to show its economic
value and significance.

CHRONOLOGICAL STUDY OF INSECT CONTROL. ite:

The matter is arranged topically as follows:

1. A general chronological study of the insect control of the boll
weevil.

2. The nature and sources of the material examined. :

3. Seasonal studies of the insect control by class of infested material.

4. A geographical study of the statistics.

5. A study of the share of insect control in the mortality of imma-
ture weevils.

6. A study of how agriculture modifies insect control.

7. Climatic considerations.

8. How insect control follows the weevil dispersion.

9. The status of the boll weevil and its control by insects.

10. A brief statement of the various classes of control exercised
upon the weevil.

11. Practical conclusions derived from statistical studies.

1. A GENERAL CHRONOLOGICAL STUDY OF THE INSECT CONTROL OF
THE BOLL WEEVIL.

Records upon parasitic control of the boll weevil begin in July,
1902, and occur more or less scatteringly until June, 1906. The
records of 1906 were very extensive, but, as will be shown, they were
merely preliminary.

Table I is arranged to show the extent of the examinations made
since 1902. This table should not be used to compare the records
of the various years, as the manner of investigation in each year has
been different, and the sources of the material have varied greatly.
The table is only intended to show the total of the examinations and
how these were distributed from year to year. <A careful analysis of
the figures has been given in the various sections of Part I.

TaBLE I.—Jnsect control of the boll weevil, by years.

Per cent mortality due to—
Weevil Preda- Para- = —
YEAR. atanae af |
stages. tors. sites. Rade Para- | All
tors. sites. insects.
DOO 2 crcclatee ecto oat Aaa ee erent ees 602 (2) 7 (?) 1.16 (?)
WOOS < Sstack.cmamc otis ocactme dooce ce scien 819 (3) 59 (2) 7.20 (?)
OOS IMET CD oye tee sere rete yoacteke eat. 2 Sane 1,005 (?) 32 (?) 3.18 (?)
WOOD PAUSUST 2:52 cee cates eeee 2 see 1, 702 (?) 21 (?) 1,23 (?)
BOG rere ee cyte = See Eo arte 40, 073 10,547 1,728 26. 31 4.31 30. 62
1S, faa re eR NS ESE rs ne 13, 602 2,279 121 16.75 8.24 24.99
OOS Spare Seine x oetais crcrste sre eeretia arsenite ee eiceee 29,349 3, 862 2,952 rks Pn lta) 10.05 23220)
POO eae et cce, Sickcinteie ie caicict ee erNnen ear tae 11, 653 1,231 620 | 10. 56 5.32 15. 88
Totals and averages................. 98,805 }.......... 6,540 |.......... TOs GM ese lacs

1 This table should not be construed as indicating that parasite control has been falling off, because
the table is based upon different kinds of examinations in different years. The detailed analysis of these
records will be found on subsequent pages,

a [24 INSECT ENEMIES OF THE BOLL WEEVIL.

The figures of 1902 are based on the total number of stages reared.
The data of 1903 are based on the total number of stages reared, but
include both stages in hanging and fallen forms. There were 654
stages in fallen forms of which 14, or 2.14 per cent, were parasit-
ized, and 165 stages in hanging forms of which 45, or 27.27 per cent,
were parasitized. The figures of 1905 were separated to show the
investigations of March and August because of the great difference
in the mortality from parasites in these two months. Between 1906
and 1909 the data represent all classes of infested material and all
infested regions. It will be noticed that for the last four years the
total insect control of the immature weevils has fluctuated between
15 and 30 per cent.

2. NATURE AND SOURCES OF THE MATERIAL EXAMINED.

During the four years 1906-1909 examinations of mortality have
been made of material collected at 6 places in Arkansas, 26 in Louisi-
ana, 6 in Mississippi, 7 in Oklahoma, and 65 in Texas, making a total
of 110 places. These examinations are based upon 94,677 stages,
involving an individual examination of over 222,700 cotton forms
(squares, blooms, and bolls). Many other collections and exami-
nations were made, but because of incomplete records are excluded
from the accompanying tables.

During the four years there has been the equivalent of examina-
tions in 176 localities, or an average of 44 localities per year.

3. SEASONAL STUDIES OF INSECT CONTROL, BY CLASS OF INFESTED
MATERIAL.

Very shortly after the work began in 1906 it became evident that
the activity of the parasites and other insect enemies of the weevil
was very different in squares and bolls, and in fallen or hanging
squares or bolls, and also that the highest control by parasites was
in hanging squares.

An examination of the squares of various varieties of cotton plants
will show the observer that certain ones have a transverse attachment
of the pedicel to the stem. In all cases where this attachment is
perfectly transverse, the square when injured by any insect is caused
to drop because of the separation of the infested part from the main
stalk by the growth of an absciss layer at the point of attachment.
(Pl. I, fig. 1; fig. 3, a.) Certain other varieties indicate a long diag-
onal attachment to the stem. When these squares are injured, a
diagonal absciss layer is formed which runs down the stem from one-
half to three-fourths of an inch or even more. This layer is gen-
erally incomplete at the lower point and consequently the square

SEASONAL STUDIES OF INSECT CONTROL. 15

hangs by a few threads and dries on the plant. (PI.J, fig. 2; fig. 3, b.)
To these squares and bolls which thus hang, we have applied the
terms “hanging squares” and ‘hanging bolls.”’

Tables II and III, which are arranged to show the monthly per-
centages of control by parasites, by predators, and by all insects,
illustrate the differences in the control of the weevil in the four
principal classes of infested material, namely, fallen and hanging dry
squares, and fallen and hanging dry bolls.

A few words of explanation of these tables are necessary in order
to show what is meant by the different classes of mortality. It has
been found that a large number of stages are destroyed as eggs or
young larve by the proliferation of the plant tissues. At the time
of the examination for mortality of the weevil, all evidence of the
weevils destroyed in these stages has disappeared; consequently the
percentages of mortality given in the following tables are the per-
centages of stages found which are killed by the causes enumerated,
and the mortality from proliferation is entirely ignored.

TaBiLE II.— Monthly mortality of the boll weevil due to insects in fallen squares.

Stages killed by— Percentage of stages killed. !
Squares} q,, _
Month. exam- Pie
ined. ‘| Cle | Preda-| Para- Total Preda-| Para- All
mate. | tors. sites. Ub £OTS; sites. | insects.
1906.
VOSA oot 2 ae ea Ske 4,476 3, 831 1,797 914 118 73. 8 23.8 3. 1 26.9
‘fib bee et oe Serene Sareea ae 7, 265 4,552 1,676 1,079 207 Gorn 23. 6 4.7 28.3
PATUISUSt aera cons chectsess sn be 19,305 | 11,186 2,828 4,097 180 63. 5 36. 6 13-7 38. 3
DOptem Perce - Ser ese een cseis 10, 709 5,365 1,475 1,625 285 63. 0 30. 2 5.4 35.6
OCTODEaa Second toteedos 1,981 600 205 133 333) 61.8 2201: 5.6 27.7
Totals and averages for
190645 sock onc sce eoee 43,736 | 25,534 7,981 7,848 823 65. 2 30. 7 3.0 34.0
1907. 5
ITC eee Pet ams oepeee aie 2,074 1, 261 339 198 76 48. 6 1556 7.0 22.6
AN bth ei 5 ee ee ae oe aera 5, 192 3, 608 778 433 133 Bie 11.9 3.8 Dt
PANTITUUIS Gee cia A olaatcatn oie 7,400 5,058 2,156 1,372 ays. 72.8 vy fa | 3.0 30. 1
Novem bers. 2 s2220.-c<2..25 150 93 90 0 1 97.7 0 1.0 1.0
Totals and averages for
OO Se Ss oe Be see ome oe 14,816 | 10,020 | 3,363 2,003 365 Gyaab 19.9 3.7 23. 6
1908.
Mary eee 2 See nee kee 100 56 4 0 2 10:7 0 3uD 3.5
AUUITIG Speak ete Rofl cicyetaiern two 7,808 5, 285 1, 169 866 324 44. 6 16. 4 6.1 22. 5
Aft Ae es ee pe ee 7,437 4, 690 1,047 902 219 46. 2 19. 2 4.7 23.9
PATUPUIS Ge iaek meee eerswcis 2 e222 1,941 1, 208 540 294 63 74. 2 24. 3 ez 29. 5
September................... 7,189 | 3,894 578 815 136 39. 2 20. 9 ono 24. 4
OGtODEr noses bon eae = eee 9,678 5, 342 807 289 659 32.3 5.4 12.3 iat,
November...........-.....-. 604 369 90 1 88 Olod Atty 22. 6 25. 3
Totals and averages for
OOS soace eeeeeeeeaee 34,757 | 20,844 45235 | 3,167 1,491 42.7 152 Goal 22.3
1909. )
JANUATY ce ae asim owes ~ ae 50 23 0 0 0 0 0 0 0
Alot; <5 ei ee See ee 7,677 4, 334 1,318 507 131 45.1 1 Per 3.0 14.7
AUIPUSGs). oo<secs cjelecinc ences --| 5,507] 2,866 680 428 38 39. 9 14.9 L3 15.2
p35} 0112) 00] 0%) ae ye eae 750 364 19 5 1 6.8 1.4 3 ee
Totals and averages for
A0)5 Bas ae 13, 984 7,587 2,017 940 170 41.2 12.4 22 14.6

-_ a

16 INSECT ENEMIES OF THE BOLL WEEVIL.

A study of Table II, on the mortality due to insects in fallen
squares, shows that the principal insect work is that of predatory
insects and, furthermore, that the total insect control is, as a rule,
less than the climatic control. The table embraces the examination
of 63,985 weevil stages of which 17,596 were killed by climate, 13,958
by predators, and 2,849 by parasites. In other words, the average
percentage of control in fallen squares by all kinds of insects is 26.2
per cent, or 21.8 per cent by predators and 4.4 per cent by parasites.

A further study of Table II shows that the predators have in each
year done their most valuable work in the month of August. The
parasites, however, have shown considerable variation in the month
of their best work. In 1906 the highest average percentage was in
October; in 1907 it was in June; in 1908 in November; and in 1909
in July.

Tasie II1.— Monthly mortality of the boll weevil due to insects in hanging squares.

Stages killed by— Percentage of stages killed.
Squares
Months. exam- prep
ined. *| Cli- | Preda-| Para- Total Preda-| Para- | All in-
mate. | tors. | sites. “1! tors. sites. | sects.
1906
Uti yee ce cee eerie ee iacae 474 247 47 20 76 57.9 8.0 21.0 29.0
INUIBUSt ose sen = aeseeeeee <a 4,165 | 2,566 539 544 337 5ds3 2152 13.1 34.3
Septem beha. s.e:222es-s-2---- 2,032 | 1,285 245 269 125 49.7 20.9 or 30.6
October a2c52 ee ee ese cee 33 20 4 10 0 70.0 50.0 0 50.0
Totals and averages for
{OOS Ree. coe ceecace 6,704 | 4,118 835 843 588 53.8 20.5 13.0 33.5
1907
RUT Je.) dere repaee Se are ee cece 150 88 26 5 13] 50.0 Dad 14.7 20. 4
VOLY pete tee cess ns 2 956 513 7 16 103 | 34.3 anil 20.1 23.2
AUMSUSE ss ccriescccciscenascee ss 3,543 | 2,011 296 175 580 52.2 8.7 28.8 37.5
Totals and averages for
POO Ta erec es seein 4,649 | 2,612 379 196 696 48.6 7.5 26.6 34.1
1908 .
JOlytosnOoscc tea cmns doc ts 25955] 2,177 395 179 479 48.4 8.2 22.0 30.2
JAUISUSE couse nt seats dsesse 1,393 842 141 91 279 60.7 10.8 33.1 43.9
Septembers.se-2-2- os he. 3,922 | 2,340 476 259 410 48.9 11.0 LTD 28.5
Octo bersecsscesteccidesceaneas 1,192 HDS 116 53 113 52.9 10.0 21.2 31.2
November.......--.--------- 1,125 10 8 0 0 80.0 0 0 0
Totals and averages for
1908% Se. cmiccdecess,c 10,587 | 5,922} 1,136 582 | 1,281 50.9 9.8 21.7 31.5
1909
JaNUaALyosc-cosesse 3 0 0 0 0 0 0 0
Julysess-c< 383 36 31 117 48.0 8.1 30.5 38.6
August... 856 96 72 88 29.9 8.4 10.3 18.7
September. is : 496 61 21 76 31.9 4.2 15.3 19.5
November........-... set 36 52 14 0 30} 100.0 0 68. 0 68.0
December. ...-.------ eces 169 47 1 71 70.4 6 42.0 42.6
Totals and averages for
1909 socieonwe aes oe 3,396 | 1,959 254 125 382 38.8 6.4 19.5 25.9

Table IIL shows that the principal insect work in hanging squares
is that of parasitic insects and, furthermore, that the total insect
control in hanging squares is each year higher than the climatic
control. This table embraces the examination of 14,611 weevil

Bul, 100, Bureau of Entomology, U. S. Dept. of Agriculture. PEATE ls

Se orematit

of

;
é
if
}

SHEDDING AND RETENTION OF FORMS ON THE COTTON PLANT.

Fig. 1.—a, b, c, Normal sears left by shed forms. Fig. 2.—a, b, e, Abnormal scars with forms
retained. Fig. 3.—a, Longitudinal section through base of shed form; 6, Longitudinal
section through base of retained form, Fig. 1, natural size: fig. 2, somewhat reduced:

fig. 3, enlarged two diameters. (After Hinds.)

SEASONAL STUDIES OF INSECT CONTROL. ley

stages of which 2,604 were killed by climate, 1,746 by predators,
and 2,897 by parasites. In other words the average percentage
of control by all kinds of insects is 31.61 per cent, or 11.93 per cent
by predators and 19.68 per cent by parasites. It appears that July
and August are usually the best months for parasite control in hang-
ing squares.

Taste [V.—Monthly mortality of the boll weevil due to insects in hanging bolls.

Stages killed by— Percentage of stages killed.
Bolls
Months. exam- poe
ined. ‘| Cli- | Preda-| Para- Total Preda-| Para- | All in-
mate. | tors. sites. ‘| tors. sites. | sects.
1906
UNC caar- oon esse stecceelsa Ae 145 0 0 0 0 0.0 0.0 0.0 0.0
UW aesecs -cciece senses ccs ee 2,947 290 28 14 0 14.5 4.8 0 4.8
PATI SUSU oe oro cia sja'seiwle'eja'errmss=iaie= 23,454 | 2,977 416 742 19 39.5 24.9 .6 Pate
S{syayiGaedle ce as ~ See etoee oe 6,210 1,555 198 188 23 26.3 12.1 AT) 13.6
OCtODer a2 ssa. 2scscec~ ss sces 399 147 21 11 3 23.8 7.5 2.0 9.5
Totals and averages for
I90G Rete aan cac merase 33,155 | 4,969 663 955 45 35.9 21.9 0.9 22.8
1907
DUNC so 26 js cen eseceee ceo. ot 50 5 1 0 1 40.0 0 20.0 20.0
GUVs pose nice slew ceiareisisie seine 50 7 1 0 0 14.3 0 0
PANIOUIS Use ts seclee sense iamc emia 1,272 330 115 51 4 51.5 15.4 1.2 16.6
Totals and averages for
L907 weiscwissec ere tec aie 1,372 342 117 51 i 50.6 14.9 1.4 16.3
1908
Ab one ee nee ie 2,227 238 34 6 21 29.7 2.5 8.8 1s
DULY eee see. tse ols reeea seca 4, 450 405 125 26 13 40.5 6.4 3.2 9.6
PATI OMI SU ee oes seis sare Scelcleneis's 1,123 200 22 20 0 21.0 10.0 0 10.0
DeMtemM bers c.o.sos- este ss ee 933 98 8 4 1 13.2 4.1 110 5.1
Totals and averages for
TODOS ese at-c- eee 8, 733 941 189 56 35 29.7 5.9 3.7 9.6
1909
JANUBLY: aes cjociaro exter. s cee os 1,616 402 133 25 dla 42.0 6.2 2.7 8.9
IGDIUANY cs = <2 cie~ oni esis 716 115 12 49 2 54.7 42.6 Le 44.3
March yiscce one asiisss en cues ss 608 56 14 12 1 48.2 21.4 herd, 23.1
Totals and averages for
VQ09! Sis cccreiacissins cies 2,940 573 159 86 14 45, 2 15.0 2.4 17.4

In fallen bolls the principal insect work is that accomplished by
predatory insects, and the total insect control has been less than
the climatic control except in the year 1906. Table IV covers an
examination of 6,825 weevil stages, of which 1,128 were killed by
climate, 1,148 by predators, and only 99 by parasites. This means
that 18.2 per cent of all the stages were killed by insects, or 16.8
per cent by predators and 1.4 per cent by parasites. In this class
of infested forms it is also noticeable that the principal work by
the predators is accomplished during the month of August.

16844°—Bull. 100—12 2

18 INSECT ENEMIES OF THE BOLL WEEVIL.

Tasie V.— Monthly mortality of the boll weevil due to insects in hanging bolls.

Stages killed by—

Percentage of stages killed.

Month. exam- ee
ined Cli- Pred- | Para- | motal Pred- | Para- All
mate. | ators. | sites. ‘| ators. | sites. | insects.
1906. |
VOL onions oe aiee tines eegodea 434 22 2 3 0 22.6 13.6 0.0 13.6
AMPUSTse. rec ons 2 ages 8,762 | 2,444 281 340 155 31.7 13.9 6.3 29. 2
DOPLCMUDEM Se mic eis ay alee sii =e 4,224 | 1,627 130 292 101 32. 1 17.9 6.2 24.1
Octobers.se5222 22sec 2s 2: 3,629 | 1,359 186 266 66 38.2 19.6 4.8 24.4
Totals and averages for
PO0G Sj esS no eS tent 17,049 | 5,452 599 901 322 33.4 16.5 5.9 22.4
1907.
Vid Wome eee eae ee ras eee 460 38 2 0 0 53 0 0 0
PAUP USD) cre ein a are te eiraree oct a 683 393 35 13 50 25. 0 3.6 12.5 16.1
Totals and averages for
190 75a 5. Bee eee: 1, 143 431 37 13 50 23.2 3.0 11.6 14.6
1908. 7
MGDTLALY selae oe. cet aee ase te 12, 451 515 424 0 54 92.8 0 10.5 10.5
March: S222 255-985 se ee eee 1, 239 22 21 0 1 100.0 0 4.5 4.5
Wy eer loeere oe mene aoe See 2,132 492 63 ays 58 32.0 fet) Teer 19.1
SANISUSU aoe ante se eee ee al 720 191 23 ih 22 27.2 3.6 11.5 15.1
DOptempers= soee ese soe oat 664 83 7 17 2 31.3 20.4 2.4 22.8
Outobennas setae asso see rane 432 262 36 11 5 19.8 4,2 1.9 6.1
INOVEIN Dero. 2202.28 ace. 2c oe 519 274 134 1 8 52.2 3 259 3.2
Totals and averages for
LOS os eae oo See 18, 157 1,839 708 73 150 50.6 3.9 8.1 12.0
1909. 7 = f
DJANUaryn sec seee ean ee 3, 941 857 335 38 43 48.5 4.4 5.0 9.4
MG DIUSLYo~ = at jesse: Seis 430 35 13 11 0 68.6 31.4 0 31.4
MarCH oc oscte ce rose arenas 653 81 16 16 0 39.5 19.7 0 19.7
PATIDUIS bles 2 oan. cee ete eee 365 42 1 2 0 8.1 5.4 0 5.4
December...... een. act 2,148 519 217 13 11 46.4 25.0 2.1 27.1
Totals and averages for
ALAC) 9/2. c=, Semen a 7,537 1,534 582 80 54 46.7 5.2 3.5 8.7

SEASONAL STUDIES OF INSECT CONTROL. 19

Table V was based, as may be seen, upon the examination of 9,256
weevil stages, of which 1,926 were killed by climate, 1,067 by pred-
ators, and 576 by parasites. In other words, the insect enemies
killed 17.74 per cent, of which 11.52 per cent were killed by predators
and 6.22 per cent by parasites. July and August are the principal
months for attack upon hanging bolls.

Summarizing the four preceding tables, Table VI is presented to
show the monthly rate of mortality in all classes of infested forms.

S

iN
‘
v.
30
&

A)
8

Fic. 1.—Diagram illustrating the monthly percentage of mortality of immature boll weevils due to
insect enemies. (Original.)

It will be noticed that in each year certain months have been omitted
and it must be explained that the reason therefor has been the
necessity of making these examinations only when other work was
not pressing. An analysis of this table is more readily made by
reference to the accompanying diagram (fig. 1), which demonstrates
conclusively that August is the month during which the insect enemies
of the boll weevil are most active.

20 INSECT ENEMIES OF THE BOLL WEEVIL.

Taste VI.—Monthly rate of mortality of the boll weevil in infested forms of all classes

Percentage of stages killed by—

Forms :
Month. exam- : Gea
ined. ¢ 7 All Ghinate Preda- Para- All
causes. es tors. sites. insects.
1906,
TUNC2. 2 ceria a's 0 cae sree emesis 4, 621 3, 831 73. 80 46. 90 23. 80 3.10 26. 90
a Ul yee aes cece treats cece 11, 120 5,111 61.67 34. 29 21.83 5.53 27. 36
AUT OUIST Me eee eee sae eee oe 55, 686 19,173 54. 64 21.19 29. 32 3.61 32. 93
PePleMDGlee see ok sea eee 23,175 9, 832 50. 40 20. 80 24.14 5.43 29. 57
OGLODEL ae a eee as acme eee ener 6, 042 2,126 44.12 19.56 19.75 4.79 24. 54
Totals and averages for 1906] 100, 644 40,073 55. 81 25.15 26. 31 4.31 30. 62
1907
VUNG oes sees coe en sa oat weseeae ae 2,274 1, 354 48. 67 27.03 14.99 6. 64 21.63
Ul yee ee aaisiasesesee secs e 6, 658 4, 166 36.55 20:11 10.77 5. 66 16. 43
PU SUSE cee ee eee eee ae eee 12, 898 7, 792 64.19 33. 39 20. 67 10.12 30.79
INOVelmMbers. se esse eee eee 150 93 97.70 96. 70 0 1.00 1.00
Totals and averages for 1907| 21, 980 13, 405 54. 27 29. 06 16.88 8. 32 25.20
1908.
MODI ary cic:n ccs .ce. Je cncseeewee 12, 451 515 92.81 82. 33 0 10. 48 10. 48
Marchis ie sane ee ae ees , 329 22 100. 00 95. 50 0 4.50 4.50
Mays aac ce tec cee Sennen ioe 100 56 10.70 7.20 0 3.50 3.50
NUN On cleetee eee eee ee Ie oe 10, 0385 5, 523 43.81 15.7 15.78 6. 24 22. 02
ALLE Me Serena ise econ erates 16, 974 7, 764 45.63 20. 99 14.73 9.90 24.63
PAUP UST SS eee testes sees e 5,177 2,441 61.53 29.79 16. 87 14.91 31.7
Septem bere seen ee ee een oe 12, 708 6, 415 42.29 16. 66 17.06 8.55 25. 61
Ocloberstcec ese coee sees eee 11, 302 6, 157 33. 92 15.57 bier 3 12.61 18. 34
NOVeEMmberes cc 3 ovecesemenesce 2, 248 653 50.53 35.52 3.06 14.70 17.76
Totals and averages for 1908 72, 234 29,546 44. 34 21.21 13.12 10.00 23.12
1909.
NANUALY 2252 52eeeese ee eee eee ee 5, 687 1, 285 45.52 36. 42 4.90 4.20 9.10
Me brary. << ecose see Sofocmscle vache 1, 146 150 58. 00 16.66 | 40.00 1. 33 41.33
IManGh occ ot aceenn. cee geeseee 1,261 137 43.06 21.89 20. 43 ff 21.15
UAE 228 cen Se eee am a ae 8, 307 erly 15. 36 28.70 11.19 5. 25 16. 34
August....... Meare Shas ee eee see 7,162 3, 764 37. 32 20. 64 13. 33 3. 34 16. 67
BOULEINDEra. ante eat ea eee 1, 495 860 21. 25 9. 30 3.02 8. 95 11.97
November...............-- ee 136 52 100. 00 32. 00 0 68.00 68. 00
IDSCEMDEN Ee Soe hose sae 2, 663 688 52. 32 38. 37 2.03 11.91 13. 94
Totals and averages for 1909 27, 857 11, 653 41.73 25. 84 10.56 5. 32 15.88

4. A GEOGRAPHIC STUDY OF THE STATISTICS OF INSECT CONTROL.

A study of these same statistics, when arranged to show the insect
control by States, has given much interesting light upon the subject
of the control of the weevil.

In fallen squares we find an average for total insect control of 26.8
per cent in Oklahoma, 25.9 per cent in Mississippi, 24.5 per cent in
Texas, 20.6 per cent in Louisiana, and 12.5 per cent in Arkansas.
Analyzing these figures from another standpoint, we find that the
State of Mississippi leads in parasite control with 14.27 per cent,
Oklahoma standing next with 4.71 per cent, Texas with 3.9 per cent,
Louisiana with 2.52 per cent, and Arkansas with 0.71 per cent. The
relative rank of the States for predatory control is quite different.
Oklahoma leads with 22.16 per cent, Texas comes next with 20.6 per
cent, Louisiana with 18.1 per cent, Arkansas with 11.82 per cent,
and Mississippi with 11.63 per cent. In climatic control Texas leads

GEOGRAPHIC STUDY OF STATISTICS. 21

with 37.9 per cent, Oklahoma comes next with 30.8 per cent, Arkan-
sas with 25.65 per cent, Louisiana with 12.5 per cent, and Mississippi
with 11.7 per cent. Thus it may be seen that the dry, prairie States
of Texas and Oklahoma lead in the climatic and predatory control
of the weevil and also in the total amount of control, and that the
climatic control in each of these States is greater than the total insect
control. This latter fact is also true of Arkansas. In Louisiana
and Mississippi, States which are naturally more humid, the climate
has less influence and the greater proportion of the control is by the
insect enemies.

In hanging squares the conditions are entirely reversed. It is
noticeable that Oklahoma leads in parasitism with an average of 31.74
per cent, Texas averages 26.6 per cent, Arkansas 24.16 per cent, Mis-
sissipi 21.2 per cent, and Louisiana 12.07 per cent. In predatory
control Louisiana leads with 12.9 per cent, Texas comes next with 10.9

PER She
10 20 ee 60

20
LOUISIANA (SSE eee 40.86 ra Letts
MISSISSIPE! Fee "Wi: (Sea
ARKANSAS Ves

TEXAS

OKLAHOMA Wiggers tee Oi see mente nee oe

Fig. 2.Diagram illustrating the average climatic and insect control of the immature boll weevils
during 1906, 1907, 1908, and 1909, in hanging squares. (Original.)

9

per cent, Mississippi with 6.98 per cent, and Arkansas with 2.55 per
cent. We have no record of predatory control in Oklahoma. In all
five States insect control in hanging squares is greater than climatic
control. With regard to climatic control Arkansas leads with 26.69
per cent, Texas has 16.8 per cent, Louisiana 15.89 per cent, Oklahoma
9.53 per cent, and Mississippi 8.12 per cent. These statistics are
graphically shown in figures 2 and 3.

A brief comparison of the condition in hanging and fallen squares will
show that the States of Texas and Oklahoma have a higher average
percentage of control from all factors in fallen squares than in the
hanging squares; the States of Louisiana and Arkansas have a higher
average percentage of control from all factors in hanging squares than
in fallen squares, and in the State of Mississippi the difference is very
slight, although in favor of the fallen squares. This illustrates the

22 INSECT ENEMIES OF THE BOLL WEEVIL.

difficulty of giving any single recommendation for the control of the
boll weevil which would apply to all regions. This point will be
brought out more fully in other sections of this bulletin.

5. A STUDY OF THE SHARE OF INSECT CONTROL IN THE MORTALITY OF
IMMATURE BOLL WEEVILS.

The condensed tables which have been presented are likely to give
the impression that the parasite control of the weevil is on an average
very low, but it must be remembered that the examinations have
been made in all parts of the infested region whether the weevil has
been present 17 years or only a few months, and whether the weevil
damage amounts to less than 1 per cent of the crop or to almost 100

one ea
<a io 50 60

O77
Conse anes
ARKANSAS ELLY: Pa a ae ees 8/8
2.52
Face ee = PREDATORS
LOUISIANA ere my —
4(3.9 ead

TEXAS & ZZ eee ze —

a 7/ 22. eral
OALAHOMA} eae! mj — 4 —

M/SS/55/°?/"e eh ae oe fod an Pa —

Fic, 3.—Diagram eS the average climatic and insect control of the immature boll weevils
during 1906, 1907, 1908, and 1909, in fallen squares. (Original.)

per cent. This great difference in the sources of the material exam-
ined has necessarily lowered the average mortality to its minimum.
The following records show some of the cases of very high mortality
due to parasites:

Highest records of parasitism of the boll weevil.
IN FALLEN SQUARES.

eee Fetal:
ei ee umber] ageo
Locality. Date. of stages. | parasit-
ism.
TRODSONG ial 2 ee erece atc ks 2g es culo Sepithen eee seers IN OVie Ol 90 fsaeeeae ees 53 77.36
Corpusi@hristts Moxes- mss a cities eee ota er 4. ee June 20, 1907...-.-.... 2 36. 95
Natchez, Miss.......... Spa), aoe oe ee eee Oct. 23, W908 sea: cece 157 28.6
DBASMN Osean ea to ga ee We Avie. 12, 1908.2. .2.- 522 18 27.78
GOHHOR MT Crxce foe eed oo, yee ener eae Sasa es July:28;1908: 20.222... 114 26. 63
INS GCHEZ MISS teh cea ee en tn ee Pe, Oct. 16, LOODSGoae ate ceme 230 PARTS
CUGTOS LOR 88 Breyer eed IO ar ee Lead Aug. 12, N90 Te Ses scene 105 19. 04
INS DGG 2 VEL SS pe ce eclectic ee July, 1909...........3 b 200 18.5
PUTeVEpOrtn a. eres cee oe een ee ee ace eee ee Oct. 29, 1908. . 2 624 15.8
VICtOTIA SL GXcs 2", < 7a cB Nee = epaiene en ae I epall June 19, 1908. 513 14.5
Hoosevel ts Mex. too S eee et ee ees oe eee ee Sept. 24, 1906. 69 14.4
PALIT COT ROX 2, aes, sees oe an ee eee July 17, 1908... 382 13.35
Brownsville, ORES sseucnat ee oe ee ee ee Sept. 5, 1906.. : 1,147 12.4
Denison, TeX...............0. enone July, 1909... pe 494 8.5
GSA ORI Beda nc eck tha, a ee Sept. 2, 1908..........- 100 8.0

SHARE OF INSECT CONTROL IN WEEVIL MORTALITY.

Highest records of parasitism of the boll weevil—Continued.
IN HANGING SQUARES.

23

ak Sorrel
F Number | ageo
Locality. Date. of stages. | parasit-
ism,
WWW CO SGX s.< tac atte rs Aas ieee nero aes July 23,.1909.5..-222-5.2 39 66.6
Xa Vin oa 0 0 Rg NS». ie co ae a CR Ser Po cskaeloaens July; 19095 acne 52 ae 55 63. 63
WACTORIS LEX.22-ceeeee. | i noe en Deh ais A dbndispdeecke Age 571907222 sews 26 61.5
Wallas, Tex....2.2ss22<: Ue Soe ee eee ee anne ee Aug. 17, 1907 82 O0s5h
JNrd Thateqioynie Ul Msb< Se SEE eg ne a ee eee a AE eee July 17, 1908. . 51 56. 86
TOSS) LENSE oA Ra a2 SiR i a na OS oe a July, 1909..... 57 52. 63
\ AVG Nob <a a ae ene Ge aan ee eee ee ee July 25, 1906 99 52.6
INAVASOta, Pex ccoets2 cece: eon. Se Be oe I hace S crmehaete AU sa. T9082 2s coseiee 29 51.75
Ne CHEZ MISS as Ae ee RR Asean se se Sees a as SSR ASEae Oct 23) 10082S25 2: soe 2x 82 51.3
San Antonio, Tex..... DS es rr a ee ae July 24, 19082-25222 29 48. 27
ET AUISt US WIIG nite eae oe tne Se SS Ae Se July Ly 190 je Seca ese 19 47.3
DEUS SOK mae iets ene Oe Ee oe ce ae enn et ATP 10; 19072 et een 193 47.15
BANGLE LON qe Reore apes cad wicls, 2 cca ricrcars cre eratts i ewicmreeis ciate lowers ATI a 65,800 8m canes oe 260 46, 92
WICLOLINy Ok cere a eno ee nee | oe ee ne ee July 29, 1908......-.-..| 140 45.71
TINO ]4 5) ety Di VShces ata. s: err ln ot AO Se Ne =, Se Re Pe a te Sbptaei lo ieee eee ce ae 22 45.47
Tallulah, eee er ot ee 2 rte ny Ae Dec. 20, 1909... 22... 85 44.7
Forbing, Uae ae ie sk Oe oI ge eM th ai Aug. 29, 1907.......... 41 43.9
RTE Ge POL are ee a nee aon a5 a oe Swe ao cages OGG 28/190 Seen omnes 37 37. 84
Ee age ete at oe) ee Mie tek WN nd 6 oes Sept. 16, 1908.......... | 69 33. 33
PAULI © clive ace Se ee ee Se Sept. 4, 1908......-...- | 63 31.74
Fouke, UW ol fee ols San oe eee AP no gece See ee ae July 27; 1908.2. 2.2.2. 284 26. 05
VVC Own ee cee eee ee he A OE eine Pee ere Aes Sept. 20, 1906.........-| 109 23.8
OE TOR GK 28 8 Oe ee a ee ee ses Atipviol, (O06. 322 ona 347 21.3
Urea Ya ea Nea ee eee ee app esa pcr eee Sass te Src Soccer sare are toncsonsyere SOD. 190 vans eo econ 495 15.35
IN FALLEN BOLLS.
Victoria, Tex..............----- ee ee Pee June 17-29, 1908......- o7| 14.4
Tlie ehoybyt Lolo. SA Ree ae, Star ee ee eS July 29, 1908......-..- 22 9.09
SIV NG Rene ate ease eae es ore a ecete cook caewis Aug. 24,1907.......... 12 8.3
fa) creo shied Be 2b: i aap gers, NCR rs a ee gr ie Nc Sept. 18,1906: ..... 2. 34 5.9
WACLOLIA LG Xe eater Si Nae er ceunea.< Riope Me ce. ai mcalae Jems, 1909% ac. areescocets 87 5.74
IN HANGING BOLLS.
Denison lex. 2225 ee en: eee Lee tet Se tak Boos ATI P27, 1907 5-2 = 20802. 11 | 36.3
Calvert, De RE ee, Te cg Coca aaa Ang. 23, 1907-2 2.2. 20 30.0
Goliad, “Toa RN eR ERE ISR i. tuly. mia TOOS Sc cee ears 38 26. 31
TE) Cy eg mr 1 ne ee ee nets | See Ones ee oe Maite, 38 | 26.31
PanbAntonios Dexa ee ee ae ee race 3, 1908S aes. 35 | 25.71
Victoria, Ts SONG Race he i Sis Lie fotucle soe pa tac Aug. 10, LOOT co enc cles 110, 22.7
Natchez, Miss Jan., 1900; 2 =. doe a 125 14.4
Marshall, Beis 5 eee eta ee es ‘Aug. 22-1906. 2. as/se cme 52 13.5
Trinity, ss RICE Dib RD ete Sirsa ee nn Arde. 9, 1906. o 2-2 cese.. 2 142 12.0
AVVO LG eee eee Oe Re wre clic os Ba Signe ered Sept. 20, 1906222.5..22.. 303 11.8

These records give merely the highest percentages for each State
ineach year. There are many other records which might be included

between the above figures.

Highest records of total insect control of the boll weevil.
IN FALLEN SQUARES.

ane , Number

Locality. Date. of stages.

Jn sei ahs dN >. Ne eo ee RPS FP Ae a Nee bse Aug. U,1007. 22 23-2 Sees 255
IMG tto Vile, Mex. fess ny ee Ca) Ree ae Aiio. Ay 1908... a cccnc~ 5. 100
OWE TOU DOR ies noah ccd ae a ae eeerte ee mea eee See Aug. 1, 19062. a 2s2. ss 197
Beeville, UN =>. ET een REE OE SFist a ace at tee] [ (6 (oe eg See 1,310
WACLOTIE DEX eo ck =, cena Se ee ot eee Se July 29, 1908.......... 375
Beeville, Tex....... Dees cress RS ne A eee eae Sept. 1, 1906........... 678
Cuero, aKa 08 Se ee ehh uh eae: June 20, 1008S nee 549
Goliad, Max one ee id. ans fae eee SO ot ee Rae AI 28, 1908. ee aes 114
Vidalia, DNAS ee RS es aos is lc 2 enc ace aa eee Sept. 15, 908i hess aoe 142

Sherman, ANS are eee age aa eect ae ele A a July, 1909.......... oes 171

Percent-
age of
insect

control.

24 INSECT ENEMIES OF THE BOLL WEEVIL.

Highest records of total insect control of the boll weevil—Continued.

IN HANGING SQUARES.

Percent-
Number | age of

Locality. Date. of stages.| insect

control.
SACHETS AA Ome tense is ae ee oie eee sien oe ee oes Eee ANEW 90 fees ee 75 84. 00
ATM ELON WOOK ee eases = DE Ee ee een July; 1909. oo 22..- oe 55 75. 44
Dallas yl Greece crete a hanes ote c cee en ae ee ee eee ope see ee 57 69. 99
VACTORISN LG Siseereeie cee e eerie eee eee eee ee eee duly 2OWLOOS Se cese 87 58. 54
WiaCOs Mex co sececiene ncn: yee) uly dy 1906S eee ees 99 56. 56
Mansneld Siac ssc sete es © Nisei neers eee ee SOpbs 1906 ssoeee eee 244 50. 90
VACTOR Ss CO Xss ee nn Se erat See Se ee peas ACO (eee ore 253 50. 00

IN HANGING BOLLS.

Manshield ie sac ct cs astenk 228 ck oe ee ee ae eee Sept. 29, 1906.......... 145 58.30
Waco, Tex..... 2G dethe Za 8 Sa Deere ene oie ee Aug. 1, 1906........... 421 42.04
Overton exe c:eeceecaamene ne See Per cere eae ae peer COs Ase Mase oe 89 40. 50
IMainstiel dl; Wia2tye-s 228 F y.t Se ei. Boe See aioe mae Sept. 24, 1906.......... 479 33. 00

THE CORRECT BASIS FOR COMPARISON OF MORTALITY STATISTICS.

As has been explained, the examinations have been made from
various sources. It is therefore necessary to arrive at some true
basis for the comparison of these data before an exact knowledge of
the conditions existing can be obtained. The first mortality of the
weevil is that due to proliferation. Dr. Hinds, in Bulletin 59 of
this bureau, has shown that the average mortality of weevil stages
in squares from proliferation is 13.5 per cent and that the average
mortality in bolls is 6.3 per cent. In the absence of further data
these two percentages are used as a basis for obtaining the weighted
average mortality.

As nearly as the proportion can be estimated throughout the entire
season, 15 per cent of the weevil stages are to be found in bolls and 5
per cent in hanging forms. Whether these arbitrary estimates be
true or not, this is the only manner in which it will be possible to
compare the mortality by the different factors in the various years.
On this basis, therefore, a series of hypothetical tables has been
erected.

In order to show how the hypothetical average differs from the
average obtained from the total examinations, two tables are given
for each year, the first being a table giving the actual conditions in
the four classes of infested material and the second table being a
hypothetical table based upon 10,000 weevil stages on the arbitrary
basis of 5 per cent of the stages in hanging forms and 15 per cent of
the stages in bolls. The process continues by first subtracting the
mortality by proliferation and then computing the mortality from
climate, predators, and parasites from the remainder. The percent-
ages of mortality given in the total line are based upon the total of
10,000 stages.

SHARE OF INSECT CONTROL IN WEEVIL MORTALITY. 25

1906.—The data on the mortality of the weevil in 1906 may there-
fore be condensed and tabulated as follows:

TaBLeE VII.—Boll-weevil mortality in 1906.

Percentage of stages killed by—
Number of | Percentage re 2 " Total ae
Wlnsston tonne! weevil of stages centage 0
stages. alive. Climate. | Predators. | Parasites, | Mortality.
i}

Hanging bollss.. 222-5 .<se2-.2s 5, 452 66. 59 10. 98 16.52 5.90 33. 41
Hanging squares..........---- 4,118 46. 20 20.30 20.50 13. 00 53.80
Mee OU Sees. es ecee eee eee 4,969 64. 53 13.34 19.01 - 90 35. 47
Mallen SQuareS <<. 55)... 2252 222. 25,534 34.80 31.20 30. 70 3.30 65. 20
Totals and averages... .. 40, 073 44.19 aya is) 26.31 4.31 55.81

TaBLE VIII.—The hypothetical or weighted average mortality of the boll weevil, 1906.)

is 1906—Mortality from—
rQ
E Prolif
= Sone Climate. | Predators. Parasites. Total.
jo) &
Class of forms. Sa] ® Is a 3 «|S oso ole ee} 3
Sul a S n| & g] & |oel S z
® | 3 |&.| 3 So |@o| © |Go| B les} 8ie.| 3
Ss w | Ss ke 3 |8s | Sa » |S) 4 | ss hy
g 2 |ss| 8 ‘a (8S! S&S |88| & |88] 8 /e8| 3B
g Spm cue e |88&| ¢ |S8| g |28|/ 8187] 8
q 518 | no = uo | a2 = =|
Co) = CB) =] o oh bs} oh 5 | oe = io) =
oO Za |e Z Se A a |e Zl Z
pleas pe va ems? | | ee
Hanging bolls........ Onv5 75| 6.30 4.7 70.310. 98 Tati lOsd2 11.6 5.90) 4.1) 37.4 ook:
Hanging squares......| 4.25] 425/13.50]57.4/ 367.6 20.30, 74.6/20.50| 75.413. 00] 47.8) 60.0| 255.2
Total hanging..| 5.00) 500'..... 62.1} 437.9]..... rye ST 0len 51.9|..... | 283.3
Fallen bolls...........| 14.25] 1,425] 6.30] 90.0 1,335.013.34| 178. 1/19.01| 253.8 .90| 12.0 37.4) 533.9
Fallen squares........ 80. 75} 8, 075/13. 50/1, 090. 1,6, 984. 9 31. 20/2, 179.330. 10/2; 144. 4) 3.30/230. 5} 69.8 5,644.3
——e | 2 — oii in
Total fallen. .... 95. 00) 9,500;...-. 1,180. 18,319. 9 a Be. ZuSD let jane. 2 89832) ee. . 242. 5)... .- (6,178.2
Totals and aver- | |
ECS ste eae ne ie 00/10, 000)12. a ‘Ll eet 24. 39)2, 439. 7\24.85)2, 485. 2 2.94 294. 4/64. 616, 461.5
)

1 Given 10,000 weevil stages.

1907 —The mortality during 1907 was 54.27 per cent when figured
from the total number of stages and total mortality, thus showing a
decrease of 1.54 per cent from the mortality of 1906 figured in the
same manner. The parasitism showed an increase of 4.01 per cent.

TaBLE 1X.—Boll-weevil mortality in 1907.

Percentage of stages killed by—

Number of | Percentage ike oc es ee Total per-

Class of forms. weevil ol'stages, |——_ |__| centage: of

stages. alive. Climate. | Predators. | Parasites. mortality.
ieneing DOSS 25255 ..-..2-305. 431 76.80 8.58 3.02 11.60 23. 20
Hanging squares.............. 2,612 51. 40 14.50 7.50 26.60 48.60
Wallen Dousi:.c2s- <<. sconce se =e 342 49. 42 31. 28 14. 91 1.46 50. 58
Fallen squares................ 10,020 42.90 33.50 19. 90 3.70 57.10
Totals and averages..... 13, 405 45.73 29. 06 16.88 8.32 54. 27

26 INSECT ENEMIES OF THE BOLL WEEVIL.

Following the plan adopted for the 1906 records these figures
may be weighted for comparison with the earlier records.

TasLe X.—The hypothetical or weighted average mortality of the boll weevil in 1907

we
i 1907—Mortality from —
gE
5
Prolifer- . . . whe Anak
z ‘ atiols Climate. | Predators. | Parasites. Potal.
ov n
+ op 6 es
5 3 = : San oe a. eg :
Class of forms. 3% 2 5 = 3 3 ‘3 S 3 gales =
oe ey et meee leet yy vet i
2 |s \|fd1 2 | 2 [28] ¢ Se] 2 28/2 182] =
~ —= o Pes o |
& | 3 |g8| 8 | @ |g8| & |e8| 2 |38| 2 188] 8
© Ele = as |/88| gg 188! € |S8/ 8 is E
o 5 ® 5 @ oH sl oH =} o#| 3 |o =]
Ay Z | a Mm |e Z | Ze Za | 4
Hanging bolls. .....-- 0.75 75) 6.30 4.7 70. 3} 8.58 6.0} 3. 02) 2. 1/11.60} 8. 1/29. 70 20.9
Hanging squares......| 4.25) 425)13.50) 57. 367. 6)14.50) 53.3) 7.50) = 27. 7/26. 60) 97. 8/55. 50) 236. 2
Total hanging..} 5.00) 500/..... 62. 1, 437. 9)..... O9F3|22 2 se | 29.8)..--- 105. 9}....- 257.1
Fallen bolls..........-} 14. 25) 1,425) 6.30 90. 0.1, 335.031. 28} 417.6)14.91) 199.0) 1.46) 19. 5/50. 90| 726.1
Fallen squares........ 80.75) 8,075,183, 50/1, 090. 1\6, 984. 9 33. 50}2, 339. 6/19. 90/1, 389. 8] 3. 70/258. 4:62. 80/5, 077.9
Total fallen.....} 95.00, 9,500)....- /1, 180. 1]8, 319. 9]... yy GY 5) eae 1,588. 8|..... lBT7aGIh cee 5, 804.0
Totals and aver- |
BSCS ..Sisen eee a 00 10, 000 T2042) 1 242d escs dee 28. 16/2, 816. 5/16. 18/1, 618. 6) 3. 83/383. 8.60. 61/6, 061.1

1 Given 10,000 weevil stages.

This table shows a weighted increase of 0.89 per cent for parasites
and a weighted decrease of 4 per cent for all agencies due to the
falling off in control by predators.

1908.—The mortality during 4908 was 44.34 per cent when figured
from the total number of stages, the total mortality thus showing
a decrease of 9.93 per cent from 1907. The parasitism showed an
increase of 1.68 per cent.

TaBLE XI.—Boll-weevil mortality in 1408.

Percentage of stages killed by—
Number of | Percentage 2
Class of forms. weevil of stages
stages. alive. Climate. | Predators. | Parasites. Ay eee
Hangin @ Dolls sees asec 1,839 49. 40 38. 48 3. 97 8.15 50. 60
Hanging squares.......-...... 5,922 49, O1 19. 24 9. 80 21.70 50. 99
Fallen bolls. .......5..--cc00s- 941 70. 25 20. 08 5.95 3. 71 29.75
Mallenisquares.).2. 25.59). .<..- | 20, 844 57. 28 20. 30 15.18 7.15 42.72
Totals and averages.....| 29,546 55. 66 21, 21 13.12 10.00 44. 34

SHARE OF INSECT CONTROL IN WEEVIL MORTALITY. 27

Following the plan adopted for the 1906 and 1907 records these
figures may be weighted for comparison with the earlier records.

TaBLE XII.— The hypothetical or weighted average mortality of the boll weevil in 1908.

& 1908—Mortality from —
5
B Prolifer.
7 ims reds - arasites Nate
= r LION: Climaie. Predators. | Parasites. Total.
88] ¢
; tg S Ss ay . . Can . ay ° = .
Class of forms. <3 ® s ee S = e = 3a Is 3
we 71 o ° ao ° o . @ pad
o°? oa o = be ra) 5 fol o 5 = o 5 = © =
& ° oo ad 2 ops) 4 ous) ed wo) Mf | bo 4
w a3 Pe us) 3d “a 3g i 3g wn | Ss =
a | 2 |e8| 2 | & |e3| & jas] & [e3/ 2 les] 3
a 2 a+ a2 3 og 2 og 2 oS 2 on a
= = = =I g Lo & Lo z 23/8 /2 =|
5 ee aco S o> | oR i) Se} 5 oe] 5 |5 }
am Za |p 4 faa im Z Ay Zi Ay qm | Zi
Hanging bolls. .....-- 0.75 75, 6.30 4.7; 70.3/38.48} 27.1) 3.97 1.4) 8.15) 5.7/51.80) 38.9
Hanging squares......] 4.25 425 13. 50 57.4] 367. 6}19. 24 70. 7} 9.80 36. 0/21. 70) 79. 8]57. 30) 243.9
Total hanging. .}| 5.00 500! besvecre Boe 437. Ole eae veel ae eeee 37.4)... 85. 5]..... 282. 8
Fallen bolls...........| 14.25] 1,425) 6. 30 90. 0/1, 335. 0/20. 08} 268.1) 5.95 79. Ae 3. 71] 49. 5/34. 10] 487.0
Fallen squares......-- 80. 75) 8,075 13. 50/1, 090. 1/6, 984. 9/20. 30/1, 417. 9/15. 18/1, 060. 3] 7. 15/499. 4/50. 30/4, 067. 7
Total fallen.....} 95.00) 9,500... .. 1,180. 1/8, 319. 9]. .... 1, 686. 0}... .. i Wa fs 4 7 | eee 548. 9} oo 4,554. 7
Totals and aver- | | |
SECS Se 22. ok. 100. 00)10, 000/12. 42/1, 242. 2)....... 17. 83/1, 783. ile hie 177.1) 6. 34,634. 4/48. 37/4, 837. 5
} |

! Given 10,000 weevil stages.

This table shows a weighted increase of 2.51 per cent for parasites
and a weighted decrease of 12.24 per cent for all agencies, due to
the falling off in control by both climate and predators.

1909.—The mortality during 1909 was 41.73 per cent when figured
from the total number of stages, the total mortality thus showing
a decrease of 2.61 per cent from 1908. The parasitism showed
also a decrease amounting to 4.68 per cent.

TaBLE XIII.—Boll-weevil mortality in 1909.

Percentage of stages killed by—
Number of | Percentage

Class of forms. weevil of stages
Stages. alive. Climate. | Predators. | Parasites. ee
Hanging bolls................. 1,534 53. 33 37. 94 5.21 S152 46. 67
Hanging squares.............. 1,959 61. 16 12. 96 6. 38 19. 49 38. 84
Fallen bolls. ..-.-22.-.--.-...- 573 54. 82 27.74 15. 00 2. 44 45.18
Fallen squares. ............... 7,587 58. 79 26. 58 12. 39 2. 24 41. 21
Totals and averages..... 11,653 58. 27 25. 84 10. 56 41.73

qr
i)
to

28 INSECT ENEMIES OF THE BOLL WEEVIL.

Following the plan adopted for the three preceding years these
figures may be weighted for comparison with the earlier records:

TaBLe XIV.—The hypothetical or weighted average mortality of the boll weevil in 1409)

g 1909—Mortality from—
q
S
e Prolifer-
= ation Climate. | Predators. | Parasites. Total.
Class of forms. SB] & |e : = meals Saale ales :
cle 3 is) as) ° Lo] ° uo) ° yoks |/i=) Lo)
ow | 2 uw} Ss uw} Ss e| Ss =|
a? ce 2, = ey oo f= ov I oY] & o 3
es eee else ciao p see) =
~ oO ey a q Sea 3) P=! 5) = Oo PL 5
I a sas a = as 5 qs 5 H3/ 8 |ae 7s
oO 3) og og og or
2 He 8 g |25| 8 |23| 8 185] 8 /e 5
BH BF 5 D Be 3 5m 3 oe] 5 |5 5
Oo ZA | a me | Z |e A | a |e a
Hanging bolls. ....... 0.75 75) 6.30) 4.7) _70.3)37.94) 26.7) 5.21 3.7] 3.52) 2.5/50.18} 37.6
Hanging squares......| 4.25) 425/13.50| 57.4] 367.6)12.96) 47.6) 6.38) 23. 4/19. 49) 71. 6/47. 29) 200. 0
paz Neen aa as eed ee
Total hanging. .} 5.00) 500)..... 62.1] 487.9}..... 74. 3)....- Pee eee (ay eee 237.6
Fallen bolls......-....| 14.25) 1,425} 6. 30 90. 0/1, 335. 0/27. 74) 370. 3/15. 00} 200. 2) 2. 44) 32. 6/48. 63) 693.1
Fallen squares....-.-.- 80. 75] 8, 075/13. 50/1, 090. 1/6, 984. 9126. 58/1, 856. 6/12. 39] 865. 4} 2. 24/156. 5/49. 14/3, 968. 6
Total fallen.....| 95.00} 9,500)... .- 1,180. 1/8, 319. 9)..... 2,226. 9)....- 17065:'6)s222 = LSOS LES 4,661.7
Totals and aver-
BUCS seme se oe 100. 00}10, 000)12. 42/1, 242.2)....... 23. 01)2, 301. 2)10.992)1, 092. 7} 2. eee 2/48. 99/4, 899. 3

1 Given 10,000 weevil stages.

This table shows a weighted decrease of 3.71 per cent for parasites
and a weighted increase of 0.62 per cent for all agencies due to an
increase in climatic control.

In the following table is given a comparison of the weighted aver-
age control by all agencies for the four years.

TasBLe XV.—Weighted average mortality of the boll weevil, 1406-1509.

Weighted average mortality due to—
Years. f
seen Climate. | Predation. | Parasites. Bare
LOO B Sie 6 ers ts a ee tw ene reine cee 12. 42 24.39 24.85 2.94 64. 61
WOU) ese ate oy = sens atone ay 5 Sees Steck ere 12. 42 28.16 16.18 3.83 60. 61
LOO So Seca ese Sea Mente oe ee 12. 42 17. 83 LT? 6.34 48. 37
TD ere pele oc re el eh Sree ay Nee oe 12. 42 23.01 10. 92 2. 63 48.99
MA VOrAce see st eee = See eee 12. 42 24. 45 15.93 3.93 56.73

In view of the fact that certain cotton varieties retain the infested
squares more than others, it is interesting to make another hypothesis
on the basis that 50 per cent of the infested forms are hanging. The
year 1908 is chosen to illustrate this phase of the subject.

SHARE OF INSECT CONTROL IN WEEVIL MORTALITY. 29

TaBLE XVI.—A hypothetical average mortality of the boll weevil in square-retaining
varieties.}

s 1908. Mortality from—
q
5
a5 Prolifera- : Preda- Saat ® 7
. 4 : ion: Climate. eee Parasites. Total.
Class of forms. Se} 2 i = i =
on n ro) H F ee he: o . | bes One| Es ° Lal
v's ‘ © o w De) © oH | ® oh} © 2 o
a cats Nea eee 3 |au| og |avlegi(sc| ag || od
5 = Bo| Adm 3 Oos| Fs |oe8 alos Rm |oo| 4s
2 GE fo?) oH GB 28] oS [Seis (ok! ok [om| ol
- ov ov ov Lv [-3)
py Nitze Dey al eels iaeie laele if ie
Hanging bolls.......- 7.50} 750) 6.3) 47.2) 702.8/38.48) 270.4] 3.97) 27.9] 8.15] 57.3] 53.7] 402.8
Hanging squares..... 42. 50) 4,250] 13.5) 573. 7/3, 676. 3/19. 24) 707.3] 9. 80/360. 3/21. 70] 797.8] 57.3)2, 439.1
Total hanging. .} 50.00) 5,000)... .. 620. 9/4, 379. 1)..... SV ied eee 388. 2)... .. Soom enees 2,841.9
Fallen bolls.......... 7.50 750) 6.3 47.2) 702.8)20.08} 141.1] 5.95) 41.8] 3.71 26.1) 34.1} 256.2
Fallen squares........ 42. 50) 4,250] 13.5] 573. 7/3, 676. 3/20. 30) 746. 3)15.18/558.1) 7.15] 262.8] 50. 3/2, 140.9
Total fallen. .... 50. 00) 5,000)... .. | 620. 9/4, 379. 1)...--. pote (ac: 9 eee 599.9) ....... 288. 9]....- 2,397.1
Totals and aver-
BPCSS oa 100. 00}10, 000)... .- 24 a8| Ssece os ag 65|1, 865.1] 9. 88/988. 1/11. 44/1, 144. 0/52. 39/5, 239.0

1 Given 10,000 weevil stages.

This series of tables, wherein the mortality of the weevil is given
an accurate basis for comparison, brings to light some very important
points. This is especially the case in Table XVI, which is based
upon the hypothesis that 50 per cent of the infested forms are hang-
ing. By comparing this hypothesis for the year 1908 with the
table of the same year in which it is considered that only 5 per cent
of the forms are hanging, it will be noticed that under the condition
of the greatest proportion of hanging squares the total control of the
weevil would be 52.39 per cent and the number of parasites to 10,000
weevil stages would be 1,154; whereas, with the smaller proportion
of hanging forms, the total control of the weevil would be 48.37 per
cent and the total number of parasites 634 to 10,000 weevil stages.
Now this shows a gain of 4 per cent in the actual control of the
weevil and almost double the number of parasites to 10,000 weevil
stages. Naturally, under such conditions it would follow that the
parasitic control would be even higher than that which has been used
as a basis for the estimate and would increase in rapid proportion.
In view of this showing of the fact that the larger the proportion of
hanging squares to the entire amount of infested forms, the larger
the insect control becomes, we recommend that those who are inter-
ested in the breeding of cotton varieties attempt to secure varieties
of cotton which will combine the necessary qualities of productive-
ness, length of lint, and early maturing with the square-retaining
tendency. It may be pointed out that the varieties known as Rublee
and Cook’s Improved are not only conspicuous for the square-retain-
ing qualities but also for their desirability under boll-weevil condi-

30 INSECT ENEMIES OF THE BOLL WEEVIL.

tions. Several other varieties have been noticed to have this
same tendency, but they have not the other characteristics to recom-
mend them. In this connection we refer the reader to section 4
(p. 21),in which it has been shown that at least two States have had
a higher average control of the boll weevil in hanging squares than in
fallen squares when all of the records available are considered. It
will also be noticed in section 5, under Table XI, giving the actual
control of the boll weevil in 1908, that hanging squares and hanging
bolls were decidedly in the lead in the total control over either fallen
squares or fallen bolls. While this has not been the case in the other
years under consideration, we nevertheless consider that the pres-
ence of a nursery for the parasites in the field is most desirable.
Undoubtedly these hanging squares constitute such a nursery.

6. A STUDY OF HOW AGRICULTURE MODIFIES INSECT CONTROL.

From studies made during 1907 the following comparisons may
be made to show the number of factors that it is actually necessary
to consider in order that differences in parasitism may be understood.

At Arlington, Tex., records were kept on a field in the red loam
post-oak country or “cross timbers,’ another in the Trinity River
bottoms, and a third on the black waxy prairie. The first was
planted March 12, the second April 1, the third April 5. On August
28 the weevil infestation of squares in the timbers was 80.5 per cent,
in the bottoms 94.3 per cent, and on the prairie 21.4 per cent. At
the same time the parasitism in fallen squares on the timbers was 3.12
per cent, in the bottoms 1.9 per cent, and on the prairie 2.56 per cent.
In the timbers the parasitism of hanging squares was 39 per cent and
in the bottoms 24.78 per cent. The variable factors are soil, flora,
time of planting, variety of cotton, and weevil abundance. Hang-
ing squares were found in 1906 to be more highly parasitized in
timber land than on the prairie, and fallen squares inversely. There
appears to be an indication of the value of early planting. This
first field was the earliest field known in the vicinity and it showed
a high parasitism in hanging forms throughout the season.

At Calvert, Tex., were two fields on the prairie, one planted March
11 and 12, the other April 1. On June 21 the weevil infestation of the
first was 18 per cent and of the second 21 per cent. On July 5 the
parasitism in the first was 2 per cent and in the second nothing.

At Denison, Tex., were two fields, one in the red clay, the other on
sandy loam, neither surrounded by timber. On the first the stalks
were burned February 28, on the second March 15. Both were
planted March 30. On August 27 the weevil infestation on the
first was 88.3 per cent, on the second 87.6 per cent; the parasitism in
fallen squares on the first was 6.31 per cent, on the second 2.85 per

HOW AGRICULTURE MODIFIES INSECT CONTROL. 31

cent; the parasitism in hanging squares on the first was 5.79 per
cent, on the second 11.53 per cent. Here the only variable condi-
tions were soil, possibly weeds, and time of plant destruction. The
parasitism in the two classes of forms was diametrically reversed.

At Terrell, Tex., were two fields on the sandy prairie, both planted
in March, but having different weeds present. The weevil infesta-
tion August 26 on one was 65.2 per cent, on the other 97.5 per cent,
while the parasitism in hanging squares on the first was 29.5 per cent
and on the second 25.6 per cent. The variables were field surround-
ings and weevil abundance.

The unknown influence which entered most of these examples was
very probably the relative abundance of the different species of para-
sites. This may best be illustrated by the hanging squares from the
timbers and bottoms at Arlington, which are quoted above. In the
timbers the determinable parasites proved to be 16 Hurytoma tyloder-
matis, 10 Microbracon mellitor, 6 Cerambycobius cyaniceps, 5 Micro-
dontomerus anthonomi, and 3 Catolaccus spp. In the bottoms there
were 17 Cerambycobius cyaniceps, 13° Microdontomerus anthonomi, 10
Eurytoma tylodermatis, 8 Catolaccus spp., and 7 Microbracon mellitor.
The rank of the species was almost entirely reversed.

Probably the most important point in the entire set of examples
is that the earliest crop had the most parasites. To show this in
another way we may refer to the conditions on the experimental farm
at Dallas. The first part of the field to put on squares was the first
part to show parasites. On July 8 infested squares were to be found
in six plats, but only on this earliest plat was there any parasitism—
5.7 per cent. On July 19 it and the adjacent plat were still consid-
erably in the lead.

That the earliest field should show the highest parasitism was
expected by the writers in view of the early spring observations.
The parasites in hibernation, whether on the boll weevil or on winter
cohosts, all reached maturity in the latter half of March at Dallas.
It was reasoned that cotton, squaring and attacked by April 15,
would get the hibernated parasites in any part of the State; that
cotton squaring and attacked by May 15 would get the first genera-
tion of parasites from the cohosts, and so on. It is reasonable to
expect that cotton with squares infested in season to attract hiber-
nated parasites or a new brood from cohosts will fare better than
cotton that commences squaring when all the parasites are concen-
trated upon neighboring cohosts. This cotton must wait until the
period of the favored cohosts begins to wane before the parasites will
begin to seek new scenes of activity. Although it was so reasoned,
it was hardly expected that there would be sufficient proof to warrant
voicing the proposition.

ao INSECT ENEMIES OF THE BOLL WEEVIL.

A series of examinations was made in the vicinity of Victoria,
Tex., in 1907 and 1908. On October 9, 1907, Mr. Cushman noted
that fall destruction of the cotton was being carried on quite exten-
sively, but in different manners. On the east side of the river, south
and east of town, was an area in which practically all of the cotton
had been defoliated by the cotton leaf-worm. This area was sepa-
rated by the river and by a wide strip of huisache timber from
other cotton areas. In other directions were located fields stripped
by grazing, some that were plowed under, and one field only was
found which had received no treatment.

On June 17, 18, and 19, 1908, fallen squares from several of these
fields were examined, with the following results:

TaBLe XVII.—Soll-weevil mortality in various cotton fields, Victoria, Tex., 1908.

| Percentage of mortality, 1908.
Treatment, 1907. Total Total.

stages. ; Breda :
Climate. tors Parasites.
Destroyed stalks, September............-..--.--.-+------ 314 | 18.18 5. 43 4.14 9. 23
Plowed, OCtonels2sse" cheese ne eee eee eae ane see 296 | 13.80 (Ee yA0) 3.00 3.00
Plowed eDeceml Dano ee sew ee ne res ne eee sae 354 | 60.70 14. 40 41.20 5. 08
Grazed, October. ... 144 | 44.40 24.30 15. 97 4.16
DO ackcec 290 | 37.50 25. 50 7.20 4.80
Defoliated. .. 480 | 29.30 20. 60 2. 50 6.20
WO ss caee : 513 | 52.80 27.00 11.10 14. 40
DO Sea. Nae So gaan ae eee eae eee ee eee 375 | 23.70 16.50 3.10 4.50

These striking differences in the percentage of control can not be
attributed to the differences of treatment in 1907, although that
may have had a bearing. The different fields had different weeds
and plants surrounding them, they received different treatment in
the spring of 1908, and there are many other reasons why no one
basis of comparison can be chosen. The table is offered to illustrate
how wide a difference in natural control can be found in fields only a
few miles apart and proves conclusively the value of individual effort
in the fight against the weevil.

Numerous other instances are contained in the notes that are quite
as striking as the one to which reference has been made. There is
every reason why each planter should follow out as complete a pro-
eram against the weevil as he can, because each effort reduces the
total infestation of his neighborhood.

7. CLIMATIC CONSIDERATIONS.

The climate of the hibernating season of 1906-7 was very unusual,
so much so that the boll weevil hardly became quiescent, and the
emergence was largely during March, whereas normally it is in
April. The boll-weevil parasites mature simultaneously with the

CLIMATIC CONSIDERATIONS. 33

great wave of boll-weevil emergence. A glance at the accompanying
diagrams (figs. 4, 5) will show that in Louisiana the monthly mean
temperature was from 3° Fahrenheit (November) to 10° (January)
higher than the normal, and in Texas it varied from normal
(November) to 10° above normal (March) during the entire winter.
On the other hand, the accumulated moisture from November 1,
1906, to March 1, 1907, in Louisiana was 5 inches below normal and
in Texas 1 inch below normal.

Cotton was planted in March and April (1907) and normally would
have squared in May and June, but it was retarded a month by the
low temperature in April and May, during which months the monthly
mean temperature was 2° to 3° below normal in Louisiana and
3° to 6° below normal in Texas. In addition to the cold of the
spring, the precipitation in Louisiana from March 1 to July 1
was 7 inches above the normal and in Texas 2 inches above. This
cold and the presence of volunteer cotton tided the boll weevil over
until the planted cotton was up. The parasites were obliged to seek
cohosts from March 15 until late in MayorinJune. The cold, damp
weather undoubtedly retarded their development so that the first
generation was ready to attack such boll weevils as were breeding
late in May and early in June. As only a few fields held this advan-
tage to the parasites, these fields naturally became much better
stocked with parasites, as has been pointed out in another paragraph.

The summer and early fall months showed a slight deficiency in
rainfall and a slightly higher mean temperature—to such an extent,
however, that the season was considered dry, for the cotton did not
put on a very luxuriant foliage, and thus gave the sun plenty of play
on the fallen squares. The result is evidenced by the high percentage
of mortality from heat shown in the mortality tables. The increase
in parasitism may be ascribed to the same cause.

The mean temperature of October, 1907, was normal in Texas, but
10° above normal in Louisiana. This warm season was followed by
a very sudden drop in temperature on November 11, the ‘‘norther’”’
lasting until the 15th. This caused the November mean in both
States to be 3° below normal (Texas 53° F., Louisiana 56° F.). In
both States during this one month the precipitation was 3 inches
above the normal. In northern Texas about 30 per cent of the adult
weevils were killed by cold. The temperature at Dallas! reached
14° on November 13, which was 11° colder than was experienced in
1906 and 21° lower than at any time in November, 1905. The boll
weevils were not prepared for this cold, as they were still in great

1 The record was made both by the minimum thermometer and the self-registering thermograph at the
laboratory in East Dallas, and is a few degrees lower than the official record at Oak Cliff, about 5 miles
to the west and across the Trinity River.

16844°—Bull. 100—12

9
2)

34 INSECT ENEMIES OF THE BOLL WEEVIL.

numbers on the plants and many immature stages were developing
in green squares and bolls.

Table XVIII gives the results of the examinations made immedi-
ately after the freeze. |

TaBLE XVIII. — Mortality of the boil weevil in Texas, November, 1907.

Mortality due to—

Place. Date. Form. Location. sg 2 Stages. eo as ii oye | a

saat: y: Para- | Other

Cold. F

sites. | Causes.

1907 Perct. | Perct.| Perct.| Per ct.
Dallasy. .. 2.20.0: Noy. 14 | Squares...} Fallen Green 93 97.7 96.7 L507 |e
WD OPees Seon |eas dossce do.... S00 see DEY ee 151 47.0 36.4 5.9 4.6
Brownwood..... Nov. 15 |...do.......| Plant...| Green... 2 100.0 | 100.0 }......- 3 | oaeforemente
Navasota.....-.- Nov. 100 |-2sdos 225/200. =--2|-= 0tee. g 100210), 00:0) ere o-oo eeeeee
Calvert.....----- 1 Sree Pio 0 Seer Qa 100.0 LOOS 0} ee ee | eee
se : 13 30.7 7.6 7.6 15.3
ae 8 Sie D)\| see aoe | Weaeeeen 37.5

7 LOOSOOF | LO0s:0)| See crea) seen
56 96.3 57.4 3.5 35.7
21 95. 2 S8s0 aa eee 57.2
16 10070 0080! |eeceee se 50.0
27 100.0 G330) cecaeeae 37.0
Totals and SQUArCSee eee ee ace sense eases 246 66.3 59.8 4.0 2.8
averages.|f-" "°°" 7" " {pins Deeb [eee eee sae! heareaiseisiers 148 88.5 49.3 2.0 237.1

Totals and

AQVETAPOSE| eee cee |ctee Meeteees| nae -meceee| acs ee eee 394 74.3 55.3 3.2 15.8

. Most of the death from “other causes” in bolls was due to proliferation, which seems to be stimulated

From this small number of stages no general statement can be made.
Of the 394 stages 55.3 per cent were killed by cold. Of the stages
in green squares or bolls, 98 per cent were killed by the cold.

The most interesting point is that although 98 out of 100 weevil
stages in green forms were killed, a parasite larva was found to have
just hatched from its egg on a weevil larva killed by cold. Three
other similar cases were found in dry forms. Seventeen cases of
parasitism were found on the 394 stages. Among these were two
living eggs of which one was an entirely new type and also two pupx
which proved to be Habrocytus piercer.

The remainder of the winter of 1907-8— that is, from December to
March 1—had a mean temperature a few degrees above the normal,
but with several severe cold spells. During the four winter months
the precipitation in both States was above the normal. The short
cold spells with warmer intervening weather and heavier rainfall
were disastrous to the boll weevil. The February examination to
ascertain the mortality of the weevil indicated about 98 per cent
mortality. Asa result of the extreme scarcity of weevils in the spring
and summer in most parts of Texas, there was a great reduction in
the number of parasites. In fact, in the northern portion of the
Texas black prairie the parasites were forced to seek other hosts. A
killing freeze in November, 1908, again killed many boll weevils.

HOW INSECT CONTROL FOLLOWS WEEVIL. 35

Following the cold of November, 1908, the winter was unusually
warm, being at least 5° F. above the normal in both Louisiana and
Texas. From March 15 to July 15, in both States, the temperature
was almost normal. However, by this time there was an accumulated
deficiency of precipitation in each State of several inches. The
months of July and August in Texas were extremely warm and many
places recorded the maximum temperatures for their entire period
of records. While the heat was less excessive in Louisiana, it never-
theless reached very high pomts. This extreme weather SHE these
two months had a tremendous effect upon the boll weevil and upon
its parasites, although records taken after some of the hottest days
showed that the mortality of the boll weevil from the heat was con-
siderably higher than the mortality of the parasites of the boll weevil.
After the middle of August a period of renewed growth of the cotton
plant gave the boll weevil an opportunity for increased development
and consequently permitted a large number of weevils to mature
before the hibernation season. Incidentally with this fall brood of
weevils, we find that there was a very great increase in the parasites,
especially in Louisiana. The following two diagrams (figs. 4, 5)
illustrate the temperature of the years under consideration.

8. HOW INSECT CONTROL FOLLOWS THE DISPERSION OF THE BOLL
WEEVIL.

From an economic standpoint it is very important to know what
kind of natural control of the boll weevil can be expected in newly
invaded country. Since 1904 it has been noticed that maximum
infestation is generally reached by August 1, and that simultaneously
an extensive dispersion of the boll weevil takes place. At this period
the boll weevils fly to fields many miles beyond the parasites. The
climatie conditions during the dispersion period are such as will not
seriously interfere with prolific breeding of the weevils in the newly
infested territory. The extent of the dispersion is limited only by
the number of weevils flying and the amount of food supply available.
In the fall of 1909 the sparse production of cotton in southern Missis-
sippi brought about a dispersion of 120 miles into new territory. |

Our knowledge of the insects which attack the boll weevil shows
that most of them are derived from the parasites of similar weevils
that are native to the region infested. Therefore, if parasites and
predators are present in the invaded region, it is reasonable to expect
that they will immediately begin attacking the boll weevil. This
assumption has been proven in many definite cases. At Minden, La.,
in 1906, a parasite larva was found in a green square infested by the
first generation. At Roxie, Miss., where the weevils had been present
only a few weeks in September, 1908, ant work and parasite work

OF THE BOLL WEEVIL.

ENEMIES

INSECT

36

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Later in the season of 1908

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STATUS OF WEEVIL AND CONTROL BY INSECTS.

9, THE STATUS OF THE BOLL WEEVIL AND ITS CONTROL BY INSECTS.

During the seasons of 1908 and 1909 the examinations of the boll
weevil to determine its status demonstrated that there had been a

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tremendous falling off of the weevil in all western and northern Texas.

In August, 1909, there was less than 10 per cent infestation in half of

88 INSECT BNEMIES OF THE BOLL WEEVIL.

Texas and in all of Oklahoma. At the same time a maximum infesta-
tion was found in all of that part of Louisiana lying south of the Red
River and in Mississippi for about 20 miles east of Natchez. An analy-
sis of the parasite records for this same season shows that the parasite
control of the weevil in these sparsely infested regions of Texas was
very light, whereas the control in the heavily infested regions of south-
ern Louisiana and Mississippi was correspondingly very high. The
inference drawn from this observation is either that the boll weevil
had ceased to be the predominating weevil species for parasitic
attack in the lightly infested region, or that the parasites had been
destroyed by the heat. That the parasites were not all destroyed
by the heat is demonstrated by many records of the same parasites
on other species of weevils during the fall and winter of 1909.

10. A BRIEF STATEMENT OF THE VARIOUS CLASSES OF CONTROL EXER-
CISED UPON THE BOLL WEEVIL.

Before passing from this part of the report, which deals with the
general conditions obtaining, it is necessary to say a few words con-
cerning the classes of control which are of importance in repressing the
boll weevil. The first agency which is responsible for mortality of the
weevils is the resistance of the cotton plant to attack, evidenced either
by the toughness of the plant tissues which must be punctured, or by
the proliferation of the tissues, which destroys the weevil eggs and
larve by crushing. When the infested form falls to the ground or
withers on the plant it becomes immediately a subject for numerous
other factors of control. Intense heat kills many stages. <A large
number of parasite species seek out infested squares for their prog-
eny; myriads of ants, beetles, and mites find nourishing food by
merely cutting their way into the infested forms and devouring the
weevil stages. In addition to these, sudden cold freezes countless
numbers of developing weevils. Neither are adults free from adverse
conditions. Many are killed by heat, or cold, or drowning; many are
picked up by birds and lizards or preyed upon by other insects; and
finally multitudes are starved on account of the ravages of other
insects upon their food supply. In this report we are able to deal
only with the three factors which are determinable in the control of
immature weevils, namely, climate, parasites, and predators.

11. PRACTICAL CONCLUSIONS DERIVED FROM STATISTICAL STUDIES.

The following conclusions of economic importance have been
reached from a study of this large series of statistics:

I. The month of August is the most important month for the con-
trol of the weevil by insect enemies. As this month is also the most

BIOLOGICAL COMPLEX. 39

important in the control affected by climate, it should be considered
as one of the most critical times of the year for controlling the boll
weevil. When a sudden drop in the temperature below freezing
occurs in the month of November before a large proportion of the
weevils has entered hibernation, and while many are still immature,
an excellent control of the species can be obtained. As, however,
this is only an occasional occurrence, it can not be relied upon and
every measure possible should have been carried out to prevent the
weevils from going into hibernation at all.

II. Hanging squares are the most important infested parts for the
work of parasites, and fallen squares in a similar degree for the work
of the predatory enemies. It has been demonstrated also that in
certain years the total control by all agencies is greater in hanging
squares than in fallen squares, and furthermore that in the more
humid States this condition is the prevalent one.

III. It has been shown by examples that the total mortality of
the weevil can be increased in proportion as the number of hanging
squares in a given area is increased and likewise that the pro-
portion of parasites to weevils is increased. It is therefore recom-
mended that plant breeders attempt to develop varieties of cotton
which will retain the squares, but will also have the other desirable
varietal characteristics necessary for the production of an early
cotton crop.

IV. The insect control of the boll weevil is dependent in a large
measure upon the operations of the farm and for this reason all those
field practices which have been included in the system of cultural
control of the boll weevil are further recommended as tending to
increase the insect control.

PART II. BIOLOGICAL COMPLEX.

In Part I of this bulletin one set of facts, composed of statistics,
was dealt with, and it was merely hinted that the causes of these con-
ditions were very complex. In this part is presented another series
of facts, even more significant than the first, but much more difficult
to present in a tangible manner. The study of these biological
factors received its first impetus when at Clarendon, Tex., in 1905,
Mr. C. R. Jones and the senior author were fortunate enough to learn
the biologies of three species of weevils and to find that all these were
parasitized more or less abundantly by the same parasites as is the
boll weevil. It was already known that some of the parasites of the
boll weevil attacked other weevils, but the significance of this fact
had not been realized.

40 INSECT ENEMIES OF THE BOLL WEEVIL.

With this simple beginning the search for other hosts of the boll-
weevil parasites was started and we have now built up the knowledge
of the following complex:

Owing to the complicated nature of the data to be presented in
this part, these have also been arranged in the following sections:

1. A list of the insect enemies of the boll weevil.

The hosts of boll-weevil parasites.

Mites which attack the boll weevil.

Flies which parasitize the boll weevil.

The hymenopterous parasites of the boll weevil.
Biological notes upon the parasites of the boll weevil.
The development of the parasites.

The distribution of the parasites.

9. The parasite seasons.

10. Adjustment to new hosts.

11. Beetles which prey upon the boll weevil.

12. Lepidopterous larvee which are incidentally predatory upon
the boll weevil.

13. Ants which prey upon the boll weevil.

14. Biology of the cohosts of the boll-weevil parasites.

15. A list of the host plants of the cohost weevils.

16. A summary of the most important biological facts.

og ee

1. A LIST OF THE INSECT ENEMIES OF THE COTTON BOLL WEEVIL.

The boll weevil is known to be attacked by 29 species of parasites,
while 20 species of predators attack the immature stages and 6
species of predators attack the adults. These species are listed as
foliows:

Arachnida.
Acarina. Sarcoptoidea.
Tarsonemide. Pediculoidine.
Pediculoides ventricosus Newport (parasite on larva), Mexico.
Pediculoides sp. (parasite on larva), Louisiana, Texas.
Tyroglyphide.
Tyroglyphus breviceps Banks (parasite on larva), Texas.
Insecta.
Orthoptera. Mantoidea.
Mantide.
Stagmomantis limbata Hahn (predator on adult), Texas.
Hemiptera-Heteroptera.
Reduviide.
Apiomerus spissipes Say (predator on adult), Texas.
Coleoptera. Adephaga.
Carabidee.
Evarthrus sodalis Le Conte (predator on adult), Louisiana, Texas.
Evarthrus sp. (predator on adult), Louisiana.

A LIST OF THE INSECT ENEMIES, 41

Insecta—Continued.
Coleoptera. Polyphaga. Diversicornia.
Cantharide.
Chauliognathus spp. (predators on larva), Louisiana, Mississippi.
Cleride.
Hydnocera pallipennis Say (predator on larva), Texas.
Hydnocera pubescens Le Conte (predator on larva), Texas.
Cucujide.
Cathartus cassiex Reiche (predator on larva), Texas.
Lepidoptera. Bombycoidea.
Noctuide.
Alabama argillacea Hiibner (defoliator, cuts off food supply).
Hymenoptera. Formicoidea.!
Dorylide.
Eciton (Acamatus) commutatum Emery (predator on larva), Texas.
Poneridee.
Ectatomma tuberculatum Olivier (predator on adult) Guatemala.
Myrmicidee. Cremastogasterine.
Cremastogaster lineolata (Say) var. clara Mayr (predator on larva) Texas.
Myrmicidze. Solenopsidine.
Solenopsis geminata (Fabricius) var. diabola Wheeler (predator on larva),
Louisiana, Mississippi, Texas.
Solenopsis molesta Say (=debilis Mayr) (predator on larva), Oklahoma.
Solenopsis tecana Emery (predator on larva), Louisiana, Texas.
Myrmicide. Myrmicine.
Monomorium minimum Buckley (predator on larva), Louisiana, Mississippi,
Texas.
Monomorium pharaonis Linneeus (predator on larva), Arkansas, Louisiana,
Oklahoma, Texas.
Pheidole sp. near flavens (predator on larva), Texas.
Pheidole crassicornis Emery (predator on larva), Texas.
Dolichoderide.
Forelius maccooki Forel (predator on larva), Texas.
Dorymyrmex pyramicus Roger (predator), Cuba.
Dorymyrmex pyramicus (Roger) var. flavus McCook (predator on larva), Texas.
Tridomyrmex analis André (predator on larva), Texas.
Formicide.
Formica fusca subpolita perpilosa Wheeler (predator on adult), Mexico.
Formica pallidi-fulva Latreille (predator on larva), Arkansas.
Prenolepis imparis Say (predator on larva), Arkansas.
Hymenoptera. Chalcidoidea.
Chalcidide. Chalcidinse. Smicrini.
Spilochalcis sp. (parasite), Texas.
Torymide. Monodontomerinz.
Microdontomerus anthonomi Crawford (parasite), Louisiana, Texas.
Eurytomide.
Eurytoma tylodermatis Ashmead (parasite), Arkansas, Louisiana, Mexico, Okla-
homa, Texas.
Bruchophagus herrere Ashmead (parasite), Mexico.
Eurytoma sp. (parasite), Texas.

1 All of these ants have been determined by Prof. William Morton Wheeler.

42 INSECT ENEMIES OF THE BOLL WEEVIL.

Tnsecta—Continued.
Hymenoptera. Chalcidoidea—Continued.
Perilampide.
Perilampus sp.' (parasite), Louisiana.
Encyrtide. Eupelmine.
Cerambycobius cyaniceps Ashmead (parasite), Arkansas, Louisiana, Mississippi,
Oklahoma, Texas.
Cerambycobius cushmani Crawford (parasite), Texas.
Cerambycobius sp. (parasite), Mississippi.
Pteromalide. Pteromalinz.
Catolaccus incertus Ashmead (parasite), United States.
Catolaccus hunteri Crawford (parasite), Louisiana, Mississippi, Mexico, Texas.
Habrocytus piercei Crawford, Louisiana, Texas.
Lariophagus tecanus Crawford (parasite), Texas.
Eulophidee. Tetrastichine.
Tetrastichus hunteri Crawford (parasite), Louisiana, Mississippi, Texas.
Hymenoptera. Ichneumonoidea.
Ichneumonide. Pimpline. Pimplini.
Pimpla sp. (parasite), Texas.
Braconide. Sigalphine.
Sigalphus curculionis Fitch (parasite), Louisiana, Mississippi, Texas.
Urosigalphus anthonomi Crawford (parasite), Texas.
Urosigalphus schwarzi Crawford (parasite), Guatemala.
Urosigalphus sp. (parasite), Texas.
Braconidze. Braconinz. Braconini.
Microbracon mellitor Say (parasite), Mexico, United States.
Braconidee.
Unknown species (parasite), Texas.
Diptera. Cyclorrhapha.
Phoride.
Aphiochxta nigriceps Loew (parasite), Texas.
Aphiochxta fasciata Fallen (parasite), Texas.
Aphiocheta pygmxa Zetterstedt (parasite), Texas.
Tachinide.
Myiophasia xnea Wiedemann (determined by Coquillett) (parasite), Texas.
Ennyomma globosa Townsend (parasite), Louisiana, Texas.

HYPERPARASITES. ”
Diptera.

Plastophora (Pseudacteon) crawfordi Coquillett on Solenopsis geminata Fabricius.
2. THE HOSTS OF BOLL-WEEVIL PARASITES.

As has just been stated, the boll weevil has 55 species of insects,
which are known to attack it. Among the parasites are to be found
7 which are occasionally accidentally hyperparasitic. At least 1 par-
asite is known to attack one of the predators. The accidental preda-
tor (Alabama argillacea) is attacked by 12 parasites, 46 predators,

1 This species may be a parasite of a Chrysopa larva or of some lepidopteron which had entered a weevil
cell.

? The enemies of Alabama argillacea Hiibner afford some interesting sidelights on the complexity of the
biological relations of cotton insects.

MITES WHICH ATTACK THE WEEVIL. 43

and 1 hyperparasite. Among these 46 predators are 6 which also
prey upon the boll weevil. At least 1 very common. predatory
insect is known to prey upon many of the boll-weevil predators.
Fifty-five species of weevils are known to be attacked as cohosts of
26 species of parasites and of the 19 species of predators which attack
the boll weevil. These 55 species of weevils are known to breed
upon 91 species of plants, most of which are to be found in the vicinity
of the cotton fields. Three of these weevils sometimes breed upon the
cotton plant. Among the great number of parasites which attack
the 55 cohost weevils, 44 species are definitely known to science and
at least 6 species of hymenopterous parasites are known to attack
these 44 species of parasites. This complexity could be carried still
further, but probably enough has been stated to show how the many
influences of nature are dependent upon one another. The state-
ments are illustrated graphically in the accompanying diagram (fig. 6).

The principal point of importance in all of these facts is that the
boll weevil has been deriving its parasites from these 51 species of
weevils and from other weevils which are not known to us, and
there is every reason to believe that some of these other 44 species
of parasites, or still additional ones to be discovered, may be drawn
over to the boll weevil as parasites in the future. The weevils serv-
ing as cohosts and the parasites are listed in the accompanying table
(fig. 7) in such manner as to show the nature of the interrelationships.

It will be noticed from this table that 6 weevils, namely, Lara
sallxi, Laria exigua, Smicraulax tuberculatus, Anthonomus albopilosus,
Tyloderma foveolatum, and Trichobaris texana each have 4 of the
boll-weevil parasites; 4 weevils are attacked by 3 of the parasites,
15 of the weevils by 2 parasites each, and the remaining 37 by only 1
parasite each.

Of the parasites, ee cyamiceps attacks 18 hosts, Hury-
toma tylodermatis attacks 16 hosts, Catolaccus wncertus 14, Catolaccus
huntert 13, and Microbracon mellitor 12. These 5 parasites are also
regarded as the most important parasites attacking the boll weevil
itself. Perhaps this importance is due to the fact that they have
a larger number of native hosts and are hence in greater abundance
around the cotton fields than the parasites having fewer native
hosts.

9

Oo. MITES WHICH ATTACK THE BOLL WEEVIL.
ACARINA. TARSONEMID#.

The mites of the genus Pediculoides are assuming an important
role among insect parasites, two species being accredited to the
boll weevil.

INSECT ENEMIES OF THE BOLL WEEVIL.

This mite has been

4-4

Pediculoides ventricosus Newport (fig. 8).
somewhat prominent in the study of the boll weevil since its first
notice in 1901 (Rangel, 1901) under the name of Pediculoides ven-

THE BOLL WEEV/IL COMPLEX.
THE COTTON PLANT

BEAK,.COWPEA
KEE VIL ALEE VIL

/

THESE NUMEROUS ENEMIES ALSO apes\ cers
ARE KNOWN 7O ATTACK AT LEAST Zi WEEVILS

WHICH ATTACK

9/
OTHER
SPECIES
OF
PLANTS
ida
FARASITES
WITH

OTHER ff
PARASITES

Fic, 6.—Diagram illustrating the boll-weevil complex. (Original.)

triculosus.

Mr. Banks has stated that it may possibly be different

from the European species, but as it is known throughout this

country under the above name it is so quoted here.

Mr. Rangel

45

PARASITES OF WEEVIL AND OTHER HOSTS.

SRLS VV! I0 AIGWNN TW1OL Tie lt us ulus SSNS SSNS SS RTS NST ISISSSSISESSNIN SISOS

EC ODEO? SEE RE EEE EERE EEE BECEEEEECEE EEC EECE EE EEE

A ee
swononsne sneswoimovoxpyA TAT PAT eee

NS RN t p
Yj Sq HR S
5% UR SW ly +2) & YH
WEP TSS HORE = 2 yes & % 9
% TIA us % K ©& S & RY &
p & See SESS Sey SSosess LFF Coky w we RF gk&s F
g SUS Laos TLSSSTSESLESSSRS FSggsusiysa & SgkSSu &
SF Rese SSsy —- SSESSESS ETT SSS oR GSLLGH Re Sg Se SLT SESS ok
VRE FT SVS SFG eGo QUT VVARG VS PHS sou g gg ch esVoss PSHSe SIN
THe HBS OKISSS TES ye SUVsgscauag SOM AS VYSRSys eS KVEH SESRKHFSTEV
SE ITRVTT SS SIRSSST STH IS Vs VSVVVyoy yes gRUIHFVesHsVce & SSES
SLC SS IV WEyRH BSN SRST US VS VSI VIII S Ve G yey GGS Gk ES 5 Souuk*oSS
TS GSON PITTS STS SVT GF SES TST STITT STS TSF T TTT Sr LH yes Vs CET Tsyse§S
s QVELSGYEWNSLSHSHSSSSssgssSs SSSUSTFGRVSIS FPS $xgye Ge Ve
SMES RSS ESC ESI SSSI SSIES SSSI SRS RSG GSES SINS SISSIES
IS 90 Ceerees STFONMEUVGYASTCSQN
w SST ELCE SUS LESS RSE CRE RRR Ree eee coe S Seg HUES eee eS CNS SER
eX X TAHT TFET YS SIs s FSS PFS I aVss PHESERTIETC TES
RS SSS § S88 SS 55 GS 8 SS ESS ETS SSS ES ES TT GS SF SG SSS GG EG EGE EKITS

(Original.)

Fic. 7.—Diagram giving the parasites of the boll weevil and their other hosts.

46 INSECT ENEMIES OF THE BOLL WEEVIL.

pointed out that these mites reproduce viviparously and that their
offspring are mature and fertile at birth. He found that when they
attach themselves to a host the abdomen commences to inflate
until it becomes many times larger than the thorax. The time
required for engorgement varies from 2 to 5 days. When the abdo-
men commences to grow, the young commence to leave the parent.
The males fertilize the females before leaving the parent’s body and
shortly afterwards die. An average of 100 female offspring to an
individual was recorded. Rangel found that in 48 hours, 21 stages
out of 40 in squares were attacked by the mites. In larger series of
tests, after four days 50 out of 153 weevil stages in squares were
attacked, or 32.6 per cent.

Fic. 8.—Pediculoides ventricosus: a, Adult female before inflation of abdomen with eggs and young;
b, adult female after inflation of abdomen with eggs and young. Greatly enlarged. (Redrawn from
Brucker.)

Pediculoides n. sp. This mite was discovered in the laboratory at
Dallas, Tex., June 13, 1907, by the senior author. Careful observa-
tions on the length of generations were made with the following
results: A gravid female was isolated June 13 and on June 17 there
were 31 gravid mites. All but 5 were removed. On June 19 there
were many offspring, one mite being well grown. On June 21 the
fourth generation began to appear. In other words, between June
13 and June 21, that is, in less than 8 days, there were two com-
plete generations. Another genealogy was as follows: Parent isolated
June 13, second generation began to appear June 14, were mature

FLIES WHICH PARASITIZE THE WEEVIL. 47

June 17, and reproducing June 19. On June 24 the third generation
was reproducing. In this case there were 11 days covering two com-
plete generations.

The mites appeared willing to feed on any insect food available,
as they were first found feeding on stages of Trichobaris compacta,
_ then on boll-weevil stages, and finally on a Baris, on boll-weevil
parasites isolated in rearing tubes, and on Hydnocera pubescens.
They were reared readily on larve of Chlorion cyaneum and Polistes
rubiginosus. Mr. John B. Railsback, of Forbing, La., found that
they attacked the larve of the bollworm and other smooth cater-
pulars very readily.

TYROGLYPHID®,

Tyroglyphus breviceps Banks was described as a weevil enemy
from Victoria, Tex. This, or a similar mite, was found to be very
abundant at Calvert, Tex., in 1906.

4, FLIES WHICH PARASITIZE THE BOLL WEEVIL.

Very few Diptera are known to be primarily parasitic upon boll
weevils, but the genera Myiophasia and Ennyomma in the Tachinide
seem to be confined to hosts of this nature. The genus Aphiocheta,
of the Phoridz, contains at least 3 species which have been reared
under circumstances pointing to primary parasitism. The larve of
the tachinids work singly and those of Aphiochzta several to a host,
but in both cases as endoparasites. When the former become full
grown they completely fill the skins of the weevil larve and fre-
quently the appendages of Myiophasia penetrate to the exterior.
The weevil skin partakes of the character of parchment and becomes
a cocoon within which the fly larva pupates and from which the
adult emerges. On the contrary the Aphiocheta larve leave the
host when they have reduced it to a shell and pupate in the weevil
cell.

The flies evidently prefer to attack weevil stages in moist, shaded
spots in preference to sunny locations. By this habit they become
very valuable in fields located in bottom lands where the dry condi-
tions conducive to parasites like the hymenopterous parasites are
absent. The puparia of Myiophasia and Ennyomma are so near
like that of the chalcidoid internal parasite Tetrastichus hunterr that
they can be differentiated only by the larger size of the dipterous
puparia.

PHORID.

Aphiocheta nigriceps Loew (determined by D. W. Coquillett).

Aphiochexta fasciata Fallen (determined by D. W. Coquillett).

Aphiocheta pygmexa Zetterstedt (determined by D. W. Coquillett).

48 INSECT ENEMIES OF THE BOLL WEEVIL.

On September 12, 1906, in dry hanging bolls collected at Dallas,
Tex., a weevil larva was found parasitized and isolated in a separate
tube, with the following record: ‘‘Very small parasite larva on small
weevil larva.’”? On September 26 a single specimen of Aphiocheta
mgriceps Loew was reared and the following note made by the
senior author: ‘‘ Found dipterous puparium, skin of hairy para-
site larva (may be the dipteron or a hymenopteron); also remains
of weevil larva.’? On October 6, 1906, in hanging bolls collected
at Dallas a weevil larva was isolated with the note, ‘‘Weevil larva
full of dipterous larve.”’ Eleven larve left this host larva and
pupated. On October 29, 7 Aphiocheta (%) fasciata Fallen and two
A. pygmexa Zetterstedt were reared. At least the latter case seems to
be very strong evidence of primary parasitism. These flies are reared
frequently from bolls and many are perhaps scavengers. Two other
species, A. epeire Brues and A. scalaris Loew, have also been reared
’ from cotton forms at Calvert, Tex. Records made in 1911, at Tal-
lulah, La., by Mr. Harry Pinkus, point conclusively to primary
parasitism.

TACHINIDA.

Myiophasia xnea Wiedemann is recorded from a number of very
important weevils. Of these, Balaninus nasicus Say (the acorn
weevil), Conotrachelus juglandis LeConte (the walnut weevil), Ampe-
loglypter sesostris LeConte (the grapevine gall-maker), Conotrachelus
afinis Boheman (the hickory-nut weevil), and Conotrachelus elegans
Say (the pecan-gall weevil) are all weevils which enter the ground for
pupation, carrying their parasites with them, and consequently it
becomes necessary for the flies to emerge from the weevil cell through
several inches of earth before attaining freedom. The only weevils
which this fly attacks and which do not enter the ground for pupation
are the boll weevil and Trichobaris compacta Casey (the Jamestown-
weed pod weevil). Very few records have been made to ascertain
its developmental period, but the three records at hand indicate from
22 to 29 days as the period from collection of the infested material
to the maturity of the fly. This period would cover largely the under-
ground period only.

Ennyomma (Loewia) globosa Townsend. Several specimens of
this fly were reared during 1907 by Mr. C. R. Jones at Alexandria,
La., as primary parasites of the boll weevil. It is a very common
parasite of Chalcodermus xneus Boheman (the cowpea-pod weevil)
in the Southern States.

5. THE HYMENOPTEROUS PARASITES OF THE BOLL WEEVIL.

So much information has been gained concerning the hymenopter-
ous parasites of the boll weevil that it will be necessary to omit
many of the technical facts learned about them. The present sec-

HYMENOPTEROUS PARASITES OF THE WEEVIL. 49

tion is concerned with the sources of the parasites and with important
records of their occurrence, while the other interesting facts to be
presented are included in the five following sections:

CHALCIDOIDEA. CHALCIDIDA. CHALCIDINH. SMICRINI.

Spilochalcis sp. A single male of this species was found dead in a
weevil cell with the remains of the weevil and its own exuvium in a
hanging square collected August 10, 1907, at Victoria, Tex.

TORYMIDZ. MONODONTOMERINA.

Microdontomerus anthonomi Crawford (fig. 9). Brachytarsus alter-
natus Say was formerly the only weevil recorded as a host of this
species. A male and female of this parasite were reared on Septem-

Fia. 9.— Microdontomerus anthonomi: Adult. Much enlarged. (Original.)

ber 12, 1907, from pods of the flowering shrub Amorpha jruticosa, at
Dallas, Tex., which were highly infested by (Bruchus) Laria exigua
Horn. In 1906, in which year this parasite was first discovered, it
ranked as seventh species in importance as a boll-weevil enemy.
In 1907 it advanced to fourth place and was very important in the
central black-prairie region of Texas. In 1909 the easternmost
limit of our records was Tallulah, La., which did not become infested
by the boll weevil until 1908.

EURYTOMID#. EURYTOMINI.

Eurytoma tylodermatis Ashmead (Bruchophagus herrere Ashmead).
This is without doubt one of the most important species under
consideration, having a range of distribution practically coexten-

16844°—Bull. 100—12——-4

50 INSECT ENEMIES OF THE BOLL WEEVIL.

sive with that of its host, the boll weevil. In previous publi-
cations it has been recorded as a parasite of Lixus musculus Say, L.
scrobicolis Boheman, Apion segnipes Say, Anthonomus heterothece
Pierce, Anthonomus squamosus LeConte, Tyloderma foveolatum Say,
and Orthoris crotchit LeConte. To this list may be added (Bruchus)
Lara exigua Horn in Amorpha pods at Dallas, Tex.; (Bruchus)
Lana salle, Sharp in pods of huisache ( Vachellia farnesiana) col-
lected at Victoria, Tex.; Spermophagus robinie Schénherr in pods of
the honey and water locusts (Gleditsia triacanthos and G. aquatica)
in Louisiana; Macrorhoptus spheralciz Pierce in pods of Spheralcia
at Del Rio, Tex.; Smicraulax tuberculatus Pierce in mistletoe stems
at Dallas, Tex.; Trichobaris texana LeConte in stems of Solanum
rostratum at Cisco and Victoria, Tex.; and also Trichobaris trinotata
Say; and finally it was reared in September, 1908, from Baris sp. in
roots of ambrosia at Camden, Ark., by C. E. Hood.

Eurytoma sp. A female primary parasite and a male accidentally
secondary on Microbracon mellitor Say were reared from hanging
squares collected August 10, 1907, at Victoria, Tex.

PERILAMPIDA.

Perilampus sp. A single individual was reared from the boll weevil
in an isolated weevil cell by C. E. Hood from squares collected Sep-
tember 7, 1907, at Shreveport, La. Another specimen of Perilampus
was reared from squares collected at Granbury, Tex., August 8, 1907,
but its source could not be proved. If it were not for the definite
record made by Mr. Hood these species could hardly be placed in
this list. This record may possibly be based upon the parasite of an
intruder in the weevil cell instead of upon the weevil itself. It is
not impossible that after several years this parasite may be found
normally as a boll-weevil parasite, as was the case with Sigalphus
curculionis.

ENCYRTIDH. EUPELMINA.

Cerambycobius cyaniceps Ashmead. The list of hosts of this spe-
cies as previously recorded included Anthonomus albopilosus Dietz,
(Bruchus) Laria obtecta Say, L. exigua Horn, Lizus musculus Say,
Trichobaris tecana LeConte, and Tyloderma foveolatum Say. To this
list may be added Laria bisignata Horn in pods of Acuan ilinoensis;
L. ochracea Schaeffer in pods of Vicia sp.; L. sallei Sharp in pods of
huisache ( Vachellia farnesiana) ; Spermophagus robin Schénherr in
pods of Gleditsia triacanthos at Alexandria, La.; Lixus scrobicollis
Boheman in stems of Ambrosia trifida and A. psilostachya; Apion
rostrum Say in pods of Baptisia tinctoria at Washington, D. C.;
Tachypterellus quadrigibbus Say in fruit of Cratzegus mollis at Vic-
toria, Tex.; Smicraular tuberculatus Pierce in stems of mistletoe

HYMENOPTEROUS PARASITES OF THE WEEVIL. 51

(Phoradendron flavescens); Tychius sordidus LeConte in Baptisia
pods at College Station, Tex.; Trichobaris compacta Casey in pods of
Datura stramonium at Paris, Tex.; and, furthermore, on Langurva
sp. in stems of Gaura sp. at Ballinger, Tex.

Cerambycobius cushmani Crawford. This parasite was reared in
small numbers as early as 1906 in southern Texas from the boll
weevil. It has been reared from Laria ochracea Schaeffer in pods of
Vicia sp.; from L. sallzi Sharp in pods of Vachellia farnesiana; from
Arecerus fasciculatus DeGeer in fruit of chinaberries ( Melia azeda-
rach) at Victoria, Tex.; and from Trichobaris texana in stems of
Solanum rostratum.

Cerambycobius sp. On February 23, 1909, a male of a green species
of Cerambycobius was reared from the weevil in squares collected at
Natchez, Miss., January 19.

PTEROMALIDX. PTEROMALINA.

Catolaceus huntert Crawford. This is the species which in all pre-
vious articles on the boll weevil has been known as Catolaccus incertus.
Its hosts as now known are Laria compressicornis Schaeffer in pods of
Acuan illinoensis; Tachypterellus quadrigibbus Say in fruit of Crategqus
spp.; Smicraulax tuberculatus Pierce in stems of Phoradendron flaves-
cens; Anthonomus xneolus Dietz in buds of Solanum spp.; Anthono-
mus albopilosus Dietz in seeds of Croton sp.; Anthonomus eugenii
Cano in fruit of pepper (Capsicum spp.); Anthonomus heterothece
Pierce in heads of /Heterotheca’ subazillaris; Anthonomus nebulosus
Le Conte in buds of Crategus spp.; Anthonomus signatus Say in buds
of dewberry (Rubus spp.); Anthonomus squamosus Le Conte in heads
of Grindelia squarrosa nuda; (Acalles) Gersteckeria nobilis Le Conte in
joints of Opuntia spp.; Zygobaris xanthoryli Pierce in berries of Xan-
thoxylum clava-herculis.

Catolaccus incertus Ashmead. This parasite is also very common
and is known from a considerable number of hosts, among which are
Laria exiqua Le Conte in pods of Amorpha fruticosa; Apion decolora-
tum Smith in pods of Merbomia paniculata; Apion griseum Smith in
pods of Phaseolus spp.; Apion nigrum Smith in buds of Robinia pseu-
dacacia; Anthonomus albopilosus Dietz in seeds of Croton spp.; Antho-
nomus aphanostepht Pierce in heads of Aphanostephus skirrobasis;
Anthonomus fulvus Le Conte in buds of Callirrhoe involucrata; Antho-
nomus nigrinus Boheman in buds of Solanum carolinense; Anthonomus
signatus Say in buds of strawberry (Fragaria virginiana); Auleutes
tenuipes Dietz in buds of Galpinsia hartweqi; Ceutorhynchus n. sp. in
crown of Selenia aurea; Baris cuneipennis Casey in roots of Helenium
tenurfolium and Calandra oryza Linneus in corn

52 INSECT ENEMIES OF THE BOLL WEEVIL.

Habrocytus piercei Crawford. This is a brilliant green parasite
resembling Catolaccus anthonomi Ashmead. It is reared from the boll
weevil mainly in the fall and from hibernated individuals in the spring.
It has been reared from Laria compressicornis Schaeffer in pods of
Acuan illinoensis. (See fig. 10.)

Lariophagus tecanus Crawford. There is every evidence that this
species 1s a true parasite of the boll weevil, although it has not been
positively reared by isolation from the boll weevil. On August 17
and 27, 1907, two specimens were reared from material collected at
Hallettsville, Tex., August 13; on August 19 and 23 three specimens
were reared from cotton squares collected at Victoria, Tex.; on August
29 three specimens were reared from squares which were collected at
Eagle Lake, Tex., on August 14. The Victoria lot was peculiar in that
it furnished the first records of Cerambycobius cushmani Crawford,
Spilochalcis sp., and Eurytoma n. sp. This species is described as a
parasite of (Bruchus) Laria prosopis Le Conte. It
undoubtedly also attacks LZ. sallei Sharp, which
also breeds in the pods of huisache; furthermore,
the species was reared from stem galls of Leucosyris
spinosus containing Anthonomus ligatus Dietz.

Tetrastichus hunter. Crawford. This interesting
new parasite of the boll weevil was first reared in
the fall of 1908 from isolated parasitized individuals
of the boll weevil collected at Natchez, Miss., by
Hi. S. Smith. It is internal in weevil larve and
pupz and has even been reared from immature
adults. A parasitized individual can easily be told
Fig. 10.—Habrocytus by its brownish color and smoothening of the vari-

piercei: Pupa. Much gyg seemental wrinkles. In more advanced stages
enlarged. (Original.) F meee =
of the parasite’s development, the parasitized in-
dividual becomes a mere brown skin of parchment. This skin serves
as puparium for the parasite. The developmental period is of con-
siderable length in the fall. Specimens isolated in November do
not mature until April or May. In 1908 it was found only at Natchez,
Miss., and Monroe, La., but in 1909 it was reared at a number of places
in Louisiana and also at Arlington, Tex. This species gives an ex-
cellent example of the adjustment of native parasites to the boll
weevil.

ICHNEUMONOIDEA. ICHNEUMONIDX. PIMPLINA.

Pimpla sp. On January 27, 1909, a larva of this species was
isolated from a weevil larva in squares collected at Nacogdoches, Tex.
This became a mature female on February 23.

HYMENOPTEROUS PARASITES OF THE WEEVIL. 53

BRACONID®. SIGALPHINAE.

Sigalphus curculionis Fitch. Previous to the summer of 1908 the
first record of rearing this species (see fig. 11) from the boll weevil was
considered doubtful, but beginning in August it was reared repeatedly
in material from Ruston and Monroe, La., and Natchez, Miss. Its
other hosts are Conotrachelus afinis Boheman in hickory nuts; Cono-
trachelus elegans Boheman in petioles of hickory at Dallas, Tex., and
in galls of Phylloxera devastatriz on pecan (Hicoria pecan) at Dallas
and Victoria, Tex.; Conotrachelus juglandis Le Conte in walnuts (/Jug-
lans nigra); Oonotrachelus nenuphar Herbst in fruit of plum, peach,
etc.; Tyloderma foveolatum Say in stems of Onagra biennis at Wash-
ington, D.C.; Trichobaris texana Le Conte in stems of Solanum rostra-
tum; Trichobaris trinotata
Say in stems of potato (Sol-
anum tuberosum); and Zygo-
baris xanthoryli Pierce in
seed of Xanthorylum clava-
herculis.

Urosigalphus anthonomi
Crawford has never been
reared since the original
records which were made
at Brownsville, Tex. Fic. 11.—Sigalphus curculionis: a, Male; b, female; c, an-

< : tenna. Allenlarged. (After Riley.)

Urosigalphus schwarz
Crawford. This Guatemalan boll weevil parasite has never been
reared in the United States.

Urosigalphus n. sp. At Arlington, Tex., in 1909, a single specimen
was reared from an isolated cocoon.

BRACONINE.

Microbracon mellitor Say.1. This parasite (see fig. 12) still holds
the lead as the most important boll-weevil parasite. Its other
host relations are only partially discovered. The following hosts
have been ascertained: Desmoris scapalis Le Conte in heads
of Sideranthus rubiginosus; Smicraulax tuberculatus Pierce in
stems of Phoradendron flavescens; Anthonomus albopilosus Dietz in
seed of Croton spp.; Anthonomus eugenit Cano in fruit of pepper

1 Bracon mellitor Say is recorded by Girault (1907) as a parasite of the lesser peach borer (Synanthedon pic-
tipes Grote and Robinson) and of the peach borer (Sanninoidea exitiosa Say). The gregarious habit of these
parasites appears to prove that the determination wasincorrect. Mr. F. E. Brooks, of West Virginia, has fur-
nished the record of this species from Sanninoidea exitiosa and also from Craponius inxqualis Say at French
Creek, W. Va. The determinations were made in the Bureau of Entomology. Dr. F. H. Chittenden states
that he reared this species from the strawberry leaf-roller, A ncylis comptana Froelich (fragariz Walsh and
Riley), at Cabin John, Md., July 9, 1899. It is probable that all parasites of Lepidoptera determined as
Bracon mellitor belong to some other species. The lepidopterous and coleopterous parasites are not dis-
tinguishable by structural characters, but are so different in habits that it is considered advisable to
call the lepidopterous parasite Microbracon dorsator Say and the coleopterous parasite M. mellitor Say.

54 INSECT ENEMIES OF THE BOUL WEEVIL.

(Capsicum spp.); Anthonomus fulvus Le Conte in buds of Callirrhoe
involucrata; Anthonomus squamosus Le Conte in heads of Grindeha
squarrosa nuda; Conotrachelus nenuphar Herbst in peaches; 7'yloderma
foveolatum Say in stems of Onagra biennis; Craponius inequalis Say in
fruit of grape (Vitis spp.), and Baris sp. in roots of Ambrosia sp.

6. BIOLOGICAL NOTES UPON THE PARASITES OF THE WEEVIL.

A number of very interesting facts, which deserve mention in an
economic bulletin, have been learned about the biology of the parasites.

ABUNDANCE OF PARASITES.

It is unusual for the parasites of the boll weevil to be found flying
in numbers. Their work is in a general way quietly and unostenta-
tiously done, but occasionally it is the privilege of the observers to
see swarms of parasites hovering around the food plant of their

favorite host. At Clar-
aa ~ fo ™ endon, Tex., in August
| . , and September, 1905, Mr.
C. R. Jones and the sen-
ior author witnessed large
numbers of Jficrobracon
nuperus and Tetrastichus
sp. hovering around the
highly infested pods of
Mentzelia nuda. The par-
asitism in pods gathered
at this time was so high
that much superparasit-
ism by Tetrastichus upon
theMicrobracon occurred.
At Ruston, La., in Octo-
Fic. 12.— Microbracon mellitor: Adult. Muchenlarged. (From ber 1907 the senior
Hunter and Hinds.) 2 ; =
author saw Catolaccus
huntert flying in all directions and resting on the flowers and
leaves of Heterotheca subaxillaris and found a very high parasitism
of Anthonomus heterothece by this species. In November, 1908,
in this same field at Ruston, a very high percentage of parasitism
of the boll weevil by Catolaccus was found. In September, 1908,
Mr. Hood saw many species of parasites around the flower heads
of Vernonia at Camden, Ark. During the same month Mr. H.S.
Smith found Catolaccus hunteri swarming on Croton capitatus contain-
ing Anthonomus albopilosus. Such observations are very important
because they suggest excellent sources for parasites to be used in
introduction experiments or suggest forcing of the parasites to the
boll weevil by the elimination of the host.

BIOLOGICAL NOTES ON THE PARASITES. 55
FREQUENTATION OF NECTARIES.

The feeding habits of adult hymenopterous parasites have long
escaped observation, but within recent years the intensive study of
parasites has proved that very little can be accomplished in the prop-
agation of parasites unless they can be fed. In the case of the para-
sites of the boll weevil it is impossible for the adults to obtain nour-
ishment from the host in which they are ovipositing, as has been
proven in the case of parasites of externally feeding insects. The
host plant of the boll weevil, however, furnishes the desired food.
The nectaries of cotton are about as plentiful as those of any other
plant. The majority of varieties of cotton have three large nectaries
on the leaves and also have them on the outside and inside of the
involucre, as well as on the inside of the flower. Frequent observa-
tions of cotton plants which were producing considerable nectar have
enabled us to observe practically all of the parasites of the boll
weevil, as well as all of the ant enemies and many other insects.
Some of these insects which visit the nectaries are injurious to the
cotton plant, but the majority seem to be beneficial. .

The quantity of nectar secreted by various varieties of cotton is
quite variable. The variety which seems to secrete more than any
other which has been observed is the Egyptian Mit Afifi. This variety
is frequently surrounded by large numbers of beneficial hymenop-
terous insects, although at the same time it appears to be very sus-
ceptible to boll weevil attack.

HELIOTROPISM.

The majority of the hymenopterous insects which have been under
observation in this investigation appear to be positively heliotropic.
In general this tendency can be utilized in rearing-cage technique to
induce the parasites to go into small tubes placed in the rearing boxes,
from which they can be easily removed. It has been noticed in
rearing cages in which there were growing plants with plenty of food,
air, and heat, that the parasites sought the lightest portion of the
cage rather than the plants which could give them some shade from
the hot sun.

The activity of the parasites is greatest when the sunlight is most
intense. Observations at the nectaries of the Egyptian cotton con-
firmed this. When the sun was shining the parasites were very
active at the nectaries and flying around the plants, but when a
cloud passed over they seemed to disappear entirely. On cloudy
days none of the Hymenoptera, except the most industrious bees and
wasps, was to be found at the nectar. Trelease (1879) states that
“the extrafloral nectar of the cotton plant is far more abundant
during night and in the early morning than at any other time, and

56 INSECT ENEMIES OF THE BOLL WEEVIL.

this is true whether we consider the involucral or foliar glands.” The
parasites probably frequent the nectaries during the morning sunlight
hours and then are equipped to go about their other duties during the
hottest part of the day.

In addition: to these actual observations as to the preference of
parasites there are other very strong proofs of heliotropism. It has
been found that there is a decided increase in the parasitism of weevil
stages in hanging forms exposed to the sun over those in fallen forms
which are more or less shaded. It is also apparent that the fallen
forms most exposed to the sun receive the greater amount of para-
sitism. Among the hymenopterous parasites there is only one at
present which seems to prefer a moist shady place for its work.
This is Tetrastichus hunteri Crawford, which is an internal parasite.

SEXES.

A numerical study of the records of rearing of parasites from the
boll weevil shows that in the majority of the species the males are
relatively fewer than the females. The following table will show the
percentage of each sex and also the number of parasites upon which
these percentages are based.

TaBLe XIX.—Relative percentages of the sexes of boll-weevil parasites.

Percentage of sexes.

' Total in-
Species. dividuals.
Female. | Male.
Per cent. | Per cent.
TMG CTOULOCOIVATICLLILON aes | oaee cee ee ae = ee ee eee ee eee bake 980 60. 78 39. 22
Catolaccus hunteri..........-.-- Ste Seale tcenin ee Se ree Peele eee safarai 809 78. 37 21. 63
Catolaccus tnCeniUsie na. = tac see eee eee oes een eee =e eee Boe 429 81.12 18. 88
Habrocytus piercei_.....-.--.------ ee er Penn a cee eee eee 30 LOOK OO" | noceoeeees
Cerambycobius cushmani .....-.---.-------+---+-- eet ieinys iamysmet aiseroeeeaee 64 71. 88 28. 12
Cera mbYCODLUS CYONICEDS 22 c- sc cecs st me osse wsne~ somes eset eae eee 509 70. 34 29. 66
GErOM0Y/COULUS|S Dee ease ecw seen ele ele poe ee mage ese se Sacra chs 1 0 100. 00
Ennyomma globosa..--...-.-.-+--+- 2 eee Mee ae ee eee oe a eae 8 37. 50 62. 50
HUT LOTUG TY LOG CRINMUTS 7 cee cee wee eens Sene eee Se eee 433 64. 90 35. 10
SEU ALT AICO TIUCE Sate te eenee Ree melas iter eB Sn esr ae eee 2 50. 00 50. 00
EOMODNOGUSTCTONUS Ror 8 Nos. Sake eos ceed ate = eae Seer eee ee 2 50. 00 50. 00
Microdoniomverus ONLNON0M 1. .5-22. co: csscca seca ee tae sees eae ee sees 223 84. 76 15. 24
MMylONNGSIO NCC sce- 222 See sca ecsc eae 5c ae es Sn ete ee 2 50. 00 50. 00
SUG CUDNUSICUTCIIION TS oo ca - = ANe n o ero eS ok rae e Srae a ets 13 61. 54 38. 46
CP ECRUSTIOCIILN TLIC TILE Dele cee was rere oe ee ee tee ee eae 41 LOO; 00) | Seances

OVIPOSITION.

Tt has been found by numerical study of the large number of para-
sites collected during the last five years that whenever the parasitism
in a field reaches between 50 and 70 per cent there is a strong likeli-
hood of reduplcation, with resulting superparasitism. The exact
records of superparasitism obtained in this investigation have been
published in another article (Pierce, 1910). Parasites have no power
of discerning the presence of another egg on the prospective hosts,
and hence there occurs at times a tremendous duplication of energies.

Bul. 100, Bureau of Entomology, U. S. Dept. of Agriculture PLATE II.

et

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EGGS OF BOLL-WEEVIL PARASITES.

Fig. 1.—Type Il. Microdontomerus anthonomi; Calvert, Tex., August 23, 1907; color white;
size 0.388 by 0.11 mm. Fig. 2.—Type VI. Unidentified egg; Dallas, Tex., November 14,
1907, color white; size 0.85 by 0.19mm, Fig. 3.—Type I. Cerambycobius eyaniceps; 3a, view
from side; 3b, view from end; color white; size about 0.8 mm. Fig. 4.—Type Il. Eury-
toma tylodermatis; Dallas, Tex., August 22, 1907; color gray; size 0.68 by 0.21 mm.; 4a, side
view of another egg. Fig. 5.—Type lV. Catolaccus hunteri; Dallas, Tex., August 22, 1907;
color white: size 0.62 by 0.22 mm. Fig. 6.—Type V. Unidentified egg; Glenmora, La.,
August 28, 1907; color gray: size 0.44 by 0.11 mm. (Original.)

. a

ae

ie

os

Bul. 100, Bureau of Entomoiogy, U. S. Dept. of Agriculture PLATE III,

PARASITES OF WEEVILS.

Fig. 1.—Eurytoma tylodermatis, pupa. Fig. 2,—Catolaccus incertus, pupa. Fig. 3.—Ceram-

bucobius cyaniceps, pupa. Fig. 4,— Mierodontomerus anthonomi, pupa. Fig. 5.—Larva of
microbracon. Fig. 6.—Microbracon mellitor, pupa. Fig. 7.—Larva of chaleidoid. Much
enlarged. (From Pierce. )

DEVELOPMENT OF THE PARASITES. 57

It may therefore be possible that a parasite will visit the same square
several times and oviposit. In general it may be said that as the
primary parasitism of the boll weevil increases the superparasitism
also increases, with the result that sometimes the parasitism might
be considerably increased if every egg reached a single host. The
following instances will illustrate this. At Calvert, Tex., 41 stages
were attacked by 44 parasites, although only 36.5 per cent of the
weevils were parasitized. If every parasite egg had reached a host,
there would have been 107.3 per cent parasitism. At Dallas, Tex.,
out of 309 weevil stages, 44.6 per cent were attacked by 216 parasites.
The possible parasitism was 69.9 per cent. Many other instances of
this kind could be given, but these two cases illustrate the condition
perfectly as it exists in many places during the fall of each year.

The time for oviposition apparently differs for the various species.
Microbracon mellitor, as a rule, oviposits before the boll-weevil larva
has constructed a cell, that is, several days before the flared square falls
or dries. Eurytoma tylodermatis appears to oviposit in squares on the
plant after the normal time of falling and hence is more important in
hanging dry squares. Catolaccus spp. and Microdontomerus antho-
nomi favor fallen forms for oviposition. The chalcids generally
oviposit after the weevil larva has formed its cell. Tetrastichus
huntert is most frequently found in fallen squares.

7. THE DEVELOPMENT OF THE PARASITES.
THE EGGS.

The eggs of the boll-weevil parasites are all oblong-elliptic and
either smooth or sculptured. The eggs of several species have at
one or both ends a small tube which is tied into a knot. Six types of
eggs of the boll-weevil parasites have been closely observed and
designated by number in the records of rearing. These are illus-
trated on Plate Il. The eggs of all the boll-weevil parasites are
placed in the weevil cell or on the larva or pupa and usually without
injuring the latter.

Type I—Type I is the egg of Cerambycobius cyaniceps. It was
determined for the species by the use of a mica plant cage in which
the parasite was isolated with newly infested squares. This ege is
about 0.8 mm. long, pure white, cylindrical, unsculptured, and with
a narrow neck, which is twisted into a knot, probably by the ovi-
positor after the latter has released it. (Plate IT, fig. 3.)

Type II.—This is the egg of Microdontomerus anthonomi, as shown
by the rearing of an isolated specimen. The color is white, the egg
being distinguished by the slightly papillose sculpture and by the
nipple at one end. It measures 0.38 mm. in length and 0.11 mm. in
breadth. (Plate IT, fig. 1.)

58 INSECT ENEMIES OF THE BOLL WEEVIL.

Type I11.—This is the egg of Eurytoma tylodermatis, found by the
isolation of a larva seen in the act of hatching, collected at Dallas,
Tex., August 22. The egg is dark-gray and thickly covered with
spines. It measures 0.68 mm. in length and 0.21 mm. in breadth.
The process at one end is frequently twisted. (Plate II, fig. 4.)

Type IV.—This egg was practically identified as that of a Cato-
laccus by isolation of specimens collected August 22 at Dallas, Tex.
The color is white and the egg is covered with very small tubercles or
papille. It is 0.62 mm. long and 0.22 mm.broad. (Plate II, fig. 5.)

Type V.—This egg was taken only at Glenmora, La., August 23,
on two weevil stages, and has not been identified. It is dark-gray °
and very spiny, but the spines are larger, longer, and sparser than in
Type Ill. The length is 0.44 mm. and the breadth 0.19 mm. (Plate
II, fig. 6.)

Type VI.—This new type was discovered November 14 at Dallas,
Tex., and has not yet been identified. There is no sculpturing what-
ever. It is pure white. The length is 0.85 mm. and the breadth
0.19mm. (Plate II, fig. 2.)

THE LARVA.

The larvee of the boll-weevil parasites live as readily on dead food
as on fresh food. The hosts generally die within a very short time
after the larve begin attack. The larve have been found pretty
well grown with dry weevil larve as food. They have been found
on weevil larve and pupe indiscriminately and several times under
the elytra of teneral or unemerged adults. Just before transforming
from the larva to pupa there is considerable meconial discharge.
The majority of the boll-weevil parasites are external feeders, but
the larve of Myiophasia xnea, Ennyomma globosa, and Tetrastichus
hunter are internal feeders. These larve kill the host in a short
time, its skin becoming shriveled and forming a perfect puparium
for the parasite. Pupation takes place within this skin. (PI. III,
HRD) fs)

Pupation.—All the chalcidoid parasites have naked pupe. The
braconids usually form silken cocoons of characteristic size, shape,
mesh, or color. The cocoons of Microbracon mellitor are very vari-
able in size, color, and consistency, so that they appear almost to
belong to different insects. The cocoons of Sigalphus curculionis are
generally of a rather bright yellow and with very fine silk. The
pupal exuvium of the various species of chalcids and braconids is
sufficiently characteristic to enable a skilled observer to determine
the species after the parasite has left. (Pl. III, figs. 1-4, 6.)

Rapidity of development.—It is rather difficult to make an accurate
study of the developmental period of parasites, especially when every
adult parasite that matures under observation must be saved, if

DEVELOPMENT OF THE PARASITES. 59

possible, for further experimentation or for determination. It is
inadvisable to isolate many of the parasites until the larva is partially
developed, as the isolation seems to dry out both food and larva.
In the study of the parasites all those in the same stage were placed
on the same tray. When they passed to the next stage in develop-
ment they were transferred to another tray. In this manner an accu-
rate record was kept of the development. In order to determine the
total length of the breeding period it seems best to take the total
period from the collection of the material to the maturity of the last
specimen and add a plus mark (+) to this figure. The total period
can hardly be more than 2 or 3 days longer than the longest period
thus obtained, as the egg period is very seldom more than 3 days.
To obtain the exact length of the pupal period, the maximum period
is taken to be the longest time from the observation of a fresh or
newly-formed pupa to maturity, and the minimum time is taken to be
the shortest period from the observation of the grown larva to ma-
turity. Having thus accurately defined the pupal stage, the relative
limits of the egg and larval stages are obtained by subtracting
the pupal stage from the total developmental period. Table XX,
which follows, presents all of the available data as they have been
reduced in this manner to show the length of development of the
various stages. It will be seen that most of the species pass their
entire developmental period in from 20 to 30 days between June and
October 15, but that after the middle of October the developing
stages are caught by the cold weather and the development is sus-
pended until spring. Thus, it is noticeable that parasites becoming
larve in early October and November have a short larval period of
probably less than 20 days, becoming pup before the cold wave
and passing a pupal period of about 150 days. Parasite larve
which hatch a little later are caught in the larval stage and hibernate
thus for from 120 to 150 days, then becoming pupe and maturing
in from 15 to 40 days. It will be noticed that Microbracon mellitor,
Hurytoma tylodermatis, and the two species of Catolaccus have short
developmental periods during the summer, while the species of
Cerambycobius have a little longer period. It will be noticed that
Habrocytus prercét has only appeared in the fall of the year. This
species has been recorded four years in succession and never before
October. On the other hand, Microdontomerus anthonomi seems to
be almost exclusively a summer parasite, having never been recorded
after September. Of course the species of which we have records
throughout the breeding season are the ones most important. This
statement is borne out by the figures on the relative numbers and
importance of the different species.

60 INSECT ENEMIES OF THE BOLL WEEVIL.

TABLE XX.—Lengths of developmental periods of the boll-weevil parasites.

Sep- |October} October | Novem- | Decem-
ember.| 1-15. 15-30. ber. ber.

Species and period. July. |August. t

Microbracon mellitor: Days. | Days.

Days. Days. Days.
9+

Her and larva ccc ccc taee 6-10 .| 6-20 | 9+ |.......... 118+
PUPS Se aaanaaes sacs ssee ccc B | 141-147 |:......... 14
DOtA sce Sep cegece ech eso see 150-++ 156+ 132+
Habrocytus piercei:
HP PeAN NanVe esc acts lace |e ceases dleecece ce Seeee mas |eaae snes 202° oscar ecicne 21+ 70+
IBD AE aie oe jc era ciara cca Smenrcta | aro aeeiree | ax oes eter | eter ILA tae me | ele ge 13+ 15+-
Se siccsieeice 34-138+4 85+

Catolaccus hunteri:

Egg and larva..........-... 70+

PUDaaesat Sats se eect. 15+

DOTA E Siractuma seerme ees c ee 85+
Catolaccus incertus:

Egg and larva 9-10+} 9-12+) 5-11+|] 9-12+] 2040 |........../.....22.../-...2.....
UDG oe Stes cla sala yr mieten Se 7-8 GH90 tI 6-82") 6-98 Nese eo eases See ae
Total. 0c. sececeecces-0 17 | U8 | 18-15 | 18+ 88-53 [lose eke Bie) eateecseeree

Cerambycobius sp.:

Beran larva sce mceecdlanescse || ceeee een aeemeeel eeeeeee leeeeeees | soeee eae | 65+
UDB crorwtats otal tas aiciasete sie iearsl | ateeainc ca| Sees See ee aa oe sa) saree ara sre | eerie ars | Care ee | ee 18+
Wotal ee ss sesve cokes epee ca totems alse eee ese Meier [Sennett lee ce ae | oe ee ae | ee ee 83+

Cerambycobius cushmani:

Mge and larvae ---cacesee|onceenes| USd- HG) a | fatter
WD Ds a; syolemlelg paseo siaieisicteinraees| assent eet [mime L | Aydt fete tetera [heen lal |
Total. wccecsmoscchcecee le scetece| D645 28. 2 BAS [co a2 hos | ee Se ee

Cerambycobius cyaniceps.:

Egg and larva..........----| 10+ | 69 | 15-19 | 16-20 | 18+ |..........].......... 84-113
WDA iereimrercistenermiaisielsiaie aveievare|\budt> © iach Oe Ls) wal (dee tlian | Ieee ag t= a | occa tore recat | eee 19-37
DO tal aca Qeionaekce sea ood 129+ 139+ 121-150

Ennyomma globosa:
Egg and larva

Eurytoma tylodermatis:
Egg and larva..............
IPI dase ane eerie

L68-f i eesemeeor 110+
20-6 | ese acce.cistale 17-25

L(S-: ee sees eeee 135+

LOTIOPhAGue TELANUS «oz sarc <6 |snnc=-c2|teeaners| AD | )|\Oec sec ns|eee teas ltoe eee naes|oseee eee ee

Microdontoi:1crus anthonomi:

Myiophasia xnea:
Wee endarVvasseciec ace cise ssccnlBe setae: Bae. "| ees a | aoe ce |

Pimpla sp.:
eT ie eUL CL EV Giese ie, ctor ee pets | fe es sradsassyel sare ore ctere | era tater erence oe | EMSS ees ee | eee 62+

Sigalphus curculionis: :
pron larva 2 sles oo 5 9 | tase Saw acer See eee| Sees Ved peeeeene] peceecoces kercrncco-

ge andilarvas.ssceaasaceselaccsces| Tea bL tales oie 8] eee ee | ene eee ee acces oe ce eee

-/-
Ota aac faces ek aoe | eter a: [once ieee eae |e eee 74-216 |. eee | pee eee

Urosigalphus anthonomi:
Egg and larva.......... Oo Jala. oes eens al bekeewe ll I6eE. ih cesoclloso eke Loe ees |r

Urosigalphus sp.:
WeranG@larva: occccaseene 4. |Home ce
PUD tates osrerta es Be eos aren eee

Ota ee ecncn dts beens | alee

DISTRIBUTION OF THE PARASITES. 61

8. THE DISTRIBUTION OF THE PARASITES.

Parasites of the boll weevil have been recorded from every part
of the territory so far invaded. The records are so numerous that
we are able to show statistically which are the most important para-
sites of the weevil. The following list gives the species in their
numerical rank for the entire period from January 1, 1906, to Jan-
uary 1, 1910, giving only the number which were accurately deter-
mined foreach species. The first seven species are the mostimportant,
as has been shown in almost every section of this report. The last
nine species may be considered as more or less adventitious or acci-
dental. These species may possibly never be recorded again, or, on
the other hand, they may become in the near future among the more
important parasites. This very event has happened in the case of
three or four of the other more important species. Up to 1906 only
four of the first five in this list had been recorded from the boll
weevil. The other species have been added since and some of them
will become very important as the weevils enter the moister wooded
regions of the East.

“TaBLE XXI.— Numerical rank of the parasites for the entire period, 1906 to 1910.

Number Number
Species. of Species. of

records. records.
Microbracon mellitor............--.-.+++- 2,147 || Ennyomma globosa................ roeenen 35
Catolaccus hunteri... Ses AOS eee 1,094 || Lariophagus teranus 8
COLOLACCUS! CN CETLUS iaic cic aio2 ease eee eee 578 || Myiophasia xnea.. 4
Eurytoma tylodermatis eter eases 575 || Eurytoma sp....- 1
Cerambycobius cyaniceps.....-...-.-.---- 574 || Cerambycobius sp 1
Microdontomerus anthonomi...-...-.---- 302 || Spilochalcis sp...-..........-----.- 1
Tetrastichus hunteri.....-2-...-02-s-0002- 168 || Urosigalphus anthonomi..........-..-.-- 1
Cerambycobius cushmani.........-.------ 18) \| CTOsigalpnus SD e 50-20 osc oo se cicec es ches 1
Sigalphus curculionis....... Beat Fe See os SPECT PUG SPocee = cae w sce ese one OL eee 1
Habrocytus pierce? ....- Fence ccs cass BOs | IED LOS eatin ptr ass doe oa ge Reale oe 1

A study of the value of these parasites by years has shown that
the majority of the species had not occupied the same rank in two
successive years. The accompanying diagram (fig. 13), giving the
yearly rank of the boll-weevil parasites from 1906 through 1909,
shows that in each year new parasites were recorded and that in some
cases these parasites continued to attack the weevil. Microbracon
mellitor appears to vary but little in importance in different seasons,
while Catolaccus hunter shows increasing importance year by year.
Some of the other parasites of considerable importance appear extremely
variable in their relative rank. It will be noticed that Habrocytus
piercet has occupied the ninth place three years in succession and
is now in eighth place. This parasite occurs in small numbers, but
may at any time become a leading parasite in Louisiana and Missis-
sippl. In addition to giving the yearly rank of the species this
diagram also shows the proportion of the sexes observed each year.

62 INSECT ENEMIES OF THE BOLL WEEVIL.

In order to show the regions in which the various species are of
greatest importance, the accompanying map (fig. 14) is presented.
This shows that while Microbracon mellitor has yielded more individuals
than the other species, it is the predominating parasite in by far the
larger proportion of the infested territory. It can also be seen that
much more can be expected from the other parasites as the weevil
moves eastward into their territory. Microdontomerus anthonomi is
quite important throughout the central black-prairie region of Texas.
Eurytoma tylodermatis is more important in north-central Texas and
also in the coast region of Texas. Cerambycobius cushmani is charac-

1906 1907 1908 1909
BRACON MELLITOR ERACON MELLITOR BRACON MELLITOR CATOLACCUS HUNTERS
| 3 [> OR a <j = _le>
CATOLACCUS INCERTUS CATOLACCUS HUNTER! CATOLACCUS HUNTER) SRACON MELL/TOR
[3[> mf cose ele] <—| se siel 4 Ee ee
CERAMEVCOBIUS CYANICEPS LURYTOMA TYLODERMATIS CATOLACCUS INCERTUS CERAMBYCOBIUS CYANICEPS

ESP i a <[ 2) Tae

CITOLACCUS HUNTER \ MICRODONIOMERUS ANTHOWON? CERAITEBYCOBIUS CYANICEPS TETRASTIONVUS HUNTER]
=< aR ame > joe: shel ¢ Lel>
EURYTOMA TYLODERMATIS TETRASTICHUS HUNTER? CATOLACCUS INCERTUS
La]> se a a
CERALIBYCOBIUS CUSHMAN MICRODONTOMTERUS ANTHONO/ |
| [> :
MMICRODONTOMERUS ANTHONO/4/ EURYTOMA TYLODERMATIS
[s[> 4 ee dd)
MYIOPHASIA AENEA LARIOPHAGUS TEXANUS HABROCYTUS PIERCE
aM <q: | «
HABROCYTUS PIERCE/ HABROCYTUS PIERCET HABROCYTUS PIERCEI S/GALPHUS CURCULIONIS
V 2 a) f >
VROSIGALPHUS ANTHONOM EURYTOMA SP. \) CRODONTOMERUS ANTHONO/I PIMPLA SP
J Ee) Ee [>
ENNYOMMA GLOBOSA CERAMBYCOBIUS CUSHMAN) UROS/GALPHUS SP.
PERILAMPUS SP MY/OPHASIA AENEA ae

SPHLOCHALCIS. SP.
oy

LARIOPHAGUS TEXANUS

Fia. 13.— Diagram illustrating yearly rank of the boll weevil parasites, 1906, 1907, 1908, and 1909.
(Original.)

teristic of the counties grouped around Victoria County, Tex., but a
few specimens have been reared from the boll weevil at Alexandria,
La., by Messrs. Cushman and Jones.

9. THE PARASITE SEASONS.

For the convenience of this work on parasites of the boll weevil,
the year has been divided into definite parasite seasons correspond-
ing with certain groups of conditions. The year opens with the
hibernation period well underway. In so far as the parasites are
concerned those which hibernate as immature insects mature gen-
erally about the middle of March. This marks the end of the hiber-

THE PARASITE SEASONS. 63

nation period or winter season and the opening of the spring season.
From March until the middle of June or sometimes July there are no
cotton squares for the weevils to breed in. Consequently the para-
sites are obliged to seek other hosts. The swmmer season is defined
as beginning with the production of squares in which the weevils and
their parasites may breed. Thus this season continues until squar-
ing ceases—that is, until late in the fall when cotton is killed by frost
and is succeeded by the winter season. However, we frequently dis-
tinguished a fall or postmigration season, which begins with the first

rT
ee ro
f|

HELP
HTS

LEN

OF MEXICO

l= CATOLACCUS /NCERTUS..
2=JETRASTICHUS HUNTERY.

Fic. 14.—Map showing the distribution of the more important parasites of the boll weevil. (Original.)

attack of weevils upon the bolls in August and ends with the heavy
frosts in October or November. The fall season is also character-
ized by a renewed growth of squares.

I. THE HIBERNATION OR WINTER SEASON.

The most important parasites which winter as immature stages
upon the boll weevil are Microbracon mellitor, Catolaccus hunteri, Ceram-
bycobius cyaniceps, Hurytoma tylodermatis, Tetrastichus hunteri, and
Habrocytus piercei. The last two species are characteristic of
winter examinations in Louisiana and Mississippi. The predatory

64 INSECT ENEMIES OF THE BOLL WEEVIL.

coleopterous larvee Hydnocera pubescens LeConte and H. pallipennis
Say are very frequently found hibernating as larve in the boll-
weevil cells or in the cocoons of Microbracon mellitor. The stage in
which these various parasites pass the winter is given very concisely
in the table of the developmental periods (Table XX) in section 7.
During January, 1910, Mr. Hood repeatedly found Eurytoma tylo-
dermatis and Catolaccus huntert hibernating in dry cotton squares
and bolls and especially in hanging moss at Mansura, La.

II. THE SPRING SEASON.

It has been demonstrated that there is a definite period between
the hibernation season and the first infestation of squares, extending
from the middle of March to the middle of June. What happens to
the parasites during this period is of considerable importance and a
great amount of work has been done in the search for intermediate
hosts.

In the case of Catolaccus hunteri the question was very satisfac-
torily answered. At Richmond, Tex., a large number of dewberry
buds infested by Anthonomus signatus was gathered March 21, 1907,
and this species of parasite was reared continuously between March
28and Aprill. At Victoria, Tex., Mr. J. D. Mitchell collected, on April
23, 1907, a lot of haws (Cratexgus mollis), infested by Tachypterellus
quadrigibbus, and on May 7 he reared this species of parasite. In-
vestigations as to the distribution of these weevils added to the
formerly known records of Anthonomus signatus in dewberry buds:
Natchitoches and Shreveport, La.; Texarkana, Ark.; Muskogee and
Ardmore, Okla.; and Trinity, Richmond, Waco, Dallas, and Mar-
shall, Tex. Tachypterellus quadrigibbus was found breeding at
Shreveport and Natchitoches, La., and Victoria, Tex.

At Dallas, Tex., the buds of Galpinsia hartweq. were found to be
infested by Auleutes tenurpes as early as April 24. This species is a
host of several species of Catolaccus. The buds of Callirrhoe involu-
crata were found at Dallas to be infested by Anthonomus fulvus as
early as April 1, and on the same date Anthonomus zeneolus was first
observed to be breeding in the buds of Solanum torreyi. Solanum
eleagnifolum, with Anthonomus xneolus both in its buds and in the
fungus leaf-galls, and Solanum rostratum with this weevil in the buds,
appeared early in April. All of these plants continued susceptible to
weevil work up to the end of the spring period, or until cotton began
to square. Numerous specimens of Catolaccus were reared from the
Solanum-infesting species of Anthonomus.

Myiophasia xnea was reared April 11, 1907, from Conotrachelus
elegans in galls of Phylloxera devastatriz on the petioles of Hicoria

THE PARASITE SEASONS. 65

pecan, collected April 2, 1907, at Victoria, Tex., and was reared June
5, 1907, from material collected May 4 at Dallas.

Sigalphus curculionis was reared in considerable numbers between
April 28 and May 7, 1907, from Conotrachelus nenuphar in plums
gathered at Texarkana, Ark., March 26; and between April 29 and
May 17, 1907, from Conotrachelus elegans in galls of Phylloxera devas-
tatrix on pecan, collected at Victoria, Tex., April 2; also between June
5 and 14, 1907, from the same species in material collected at Dallas,
Tex., May 4.

Cerambycobius cyaniceps was studied very carefully at Victoria,
Tex., by Mr. J. D. Mitchell during the winter of 1909-10 as an
enemy of Trichobaris texana in stems of Solanum rostratum, and of
Lizus scrobicollis in stems of Ambrosia trifida. Mr. T. T. Holloway
conducted experiments in longevity by feeding sugared water to the
parasites. Emergence began, in the lots of Trichobaris, on February
1 and continued until April 8. The last parasite lived until May 31.
The total period of activity was 119 days and the average period
lasted from March 11 to April 1. The longest record of longevity
was 71 days and the average 21 days. Emergence began from the
lots of Lixus on March 2 and continued until March 24. The last
parasite lived until May 11. The total period of activity was 70
days and the average period was between March 13 and April 4.
The longest record of longevity was 67 days and the average 22.

Eurytoma tylodermatis was reared from the same lots and treated
in the same manner. Emergence began from the lots of Trichobaris
on February 3 and continued until March 21. The last parasite
lived until April 30. The total period of activity was 86 days and
the average period was between March 10 and March 30. The longest
record of longevity was 42 days, and the average 20 days. Emergence
began from the lots of Lixus on February 22 and lasted until April 17.
The last parasite lived until June 1. The total period of activity
was 99 days and the average period lasted from March 16 to April 11.
The longest record of longevity was 79 days and the average 26 days.

III. THE SUMMER SEASON.

The first boll-weevil parasites of the year are reared late in May or
early in June in southern Texas, but in a very short time squares are
forming all over the entire cotton belt and parasites may be found
everywhere in small numbers as the summer progresses. The per-
centage of parasitism increases rapidly and generally becomes very
high after August 1. Most of the important parasites may also be
found on their normal summer hosts.

16844°—Bull. 100—12 5

66 INSECT ENEMIES OF THE BOLL WEEVIL.

About the middle of August squares commence to fail, and few
squares are to be found by September 1. This condition may be
said to begin the fall season, when the parasites are largely obliged
to seek other hosts or to attack the boll weevil in bolls.

IV. THE FALL OR DISPERSION SEASON.

Coincident with the decline in square production is the beginning
of the boll-weevil dispersion which extends into new territory around
the entire periphery of the infested region. In the fall there is a new
growth of squares which furnishes food for the weevils before entering
hibernation and also furnishes an opportunity for very high parasitism
just preceding hibernation. It is during this season that parasite
swarms are recorded and hence this is a very critical time for obtaining
and transferring desirable parasites to new regions. During this early
fall season there are several very important ways of propagating the
parasites already present in the vicinity, as will be shown later. The
fall season of the year closes abruptly with the first killing frost, for
this crisis precipitates the hibernation period.

10. ADJUSTMENT TO NEW HOSTS.

It is a very striking fact that the continuously breeding boll
weevil is attacked by parasites which in many instances attack nor-
mally weevils having but asingle generation annually. Some of these
parasites attack one host after another throughout the entire breeding
season and may be found in activity at all periods except during
hibernation. This condition is well illustrated by the accompanying
diagram (fig. 15) giving the seasonal rotation of Catolaccus hunteri
and Oerambycobius cyaniceps. Whether these parasites were origi-
nally single-generation species like their hosts is a question we can not
now decide, but we now know that they have become adapted to
many species. This fact can be most easily proven by reference to
the list of hosts of the boll-weevil parasites given in the second section
of this part (p. 42). It appears possible that the constantly changing
factors of nature cause the various species to be continually adjusting
their habits to new environments and new hosts. In other words, the
groups of parasites from which the most available enemies of a new or
introduced species may be obtained are those groups in which the
parasitic habits are the most variable. A parasitic species that is as
readily at home on a stem weevil as on a bud or seed weevil is probably
able to attack many different species.

The most striking example of the adjustment of new parasites was
furnished in 1907. <A lot of hanging squares collected by Mr. J. D.
Mitchell on August 5, 1907, at Victoria, Tex., on a field known as the
Haskell field gave a percentage of 61.5. There was something so

ADJUSTMENT TO NEW HOSTS. 67

striking about the nature of the record that Mr. Cushman was sent
immediately to Victoria to study the surroundings of this field and
report upon the possible reasons for the high percentage of parasitism.
Mr. Cushman reported after considerable study that there were
only two factors which, it seemed to him, might have an influence
upon the parasites of the boll weevil. The first factor was the com-
plete lack of fruit upon the huisache trees (Vachellia farnesiana)
which is the normal food of Laria sallxi. The second factor noticed
was the absence of flowers on the Callirrhoe involucrata, the host of
Anthonomus fulvus. Mr. Cushman reasoned that the point would be
proven if we should rear from the boll weevil some of the character-
istic parasites of either this or the other species. As a result of
rearings from the material collected in this field, the principal par-
asite was Microbracon mellitor, the typical boll weevil parasite, but a

SEASONAL ROTATION OF HOSTS BY eee HUNTER! CRAWFORD.
| YUE _ |

rus. SAY
ie OMUS AENEOLUS BOMEMAN
a | a ee

GRANOIS BOHEMAN

TACHYPTERELLUS _QUAORIGIEBUS SAY
T¥CHYUS. SORDIDUS a
—lecadetes copsnscet d comeascTaA Gaser
ae cRaMo/s SOHEMAN | AyrHonond eee (S__GRANLY.

Bead el RIS TEXAWA LECONTE
TRL)
zz RAULAX_TUBERCULATUS. PERCH
(SEES Et =! Pena MESSE

Fia. 15.—Diagram illustrating the seasonal rotation of hosts of Catolaccus hunteri and Cerambycobius
cyaniceps. (Original.)

species which 1s also a typical parasite of Anthonomus fulvus. It
is probable that the latter species furnished some of the Micro-
bracons for this infestation. The next most important species was
Cerambycobius cushmani, a typical parasite of Laria sallxi and of
Arecerus fasciculatus which breeds in the fruit of the chinaberry tree
(Melia azederach). In addition to this species, this same field yielded
3 other new parasites of the boll weevil, 2 of which are known to
be parasites of the Laria. These were Eurytoma sp., Spilochalcis sp.,
and Lariophagus texanus.

To illustrate the divergence of habits among parasites the host
relations of Catolaccus incertus may be cited. This parasite attacks
several species of Laria (Bruchus) which are internal seed eaters and
pupate in their feeding cells; such weevils as Zygobaris xanthoxyli and
Auleutes tenuipes, which are seed or bud feeders and pupate in the

68 INSECT ENEMIES OF THE BOLL WEEVIL.

ground; and Anthonomines, which dwell in buds (Anthonomus gran-
dis), in flowers (A. aphanostephi), and in hard seed (A. albopilosus).
But it draws the line apparently at stem dwellers and is replaced by
Neocatolaccus tyloderme on Lixus, Tyloderma, and Ampeloglypter.
Cerambycobius cyaniceps is as much at home in a stem as ina bud,
and so also are Eurytoma tylodermatis and Microdontomerus anthonomi.
The Braconide appear to be more particular as to food but the most
noted of all, Microbracon mellitor, has no preferences between stem
dwellers and bud dwellers.

Thirteen miles southeast of Yazoo City, Miss., on November 1, 1909,
the senior author found an isolated artificial focus of infestation by
the boll weevil over 30 miles from any infestation of the same age
and 20 miles beyond the regularly infested region. Out of 8 squares
picked, containing 5 stages, 1 parastized stage was found.

11. BEETLES WHICH PREY UPON THE BOLL WEEVIL.

The attack of the insects predatory on the adult boll weevil is purely
accidental. They may be very numerous, but the only ones recorded
and verified are Evarthrus sodalis Le Conte and another species of the
same genus. There are, however, several insects which have an actual
value through their established habit of either breeding in the square
upon the boll-weevil stages or of entering the square and consuming
the weevil. We shall refer to four of them.

Hydnocera pallipennis Say. A single beetle of this species was
reared April 6, 1907, after 183 days in its cocoon, and over 214 days
isolation in the rearing tube. It was collected in a boll-weevil cell at
Waco, Tex., August 28, 1906. The cocoon is very finely threaded,
loosely woven, and only single layered. The stage of the beetle can
easily be observed at any time.

Hydnocera pubescens Le Conte. This clerid is a very common
breeder in the weevil cells. Its larvee have been found not only
feeding upon the various weevil stages but have been taken frequently
from Microbracon cocoons which they have entered at a much
younger stage.

Cathartus gemellatus Duval. This cucujid beetle is both a predator
and a scavenger, its larvee being frequently found, however, feeding
upon boll-weevil stages which they must have killed.

Chauliognathus spp. The larve of these lampyrid beetles are very
common in the squares and bolls of cotton in Louisiana and Missis-
sippi. In one instance undoubted proof of the attack of such a larva
upon one boll-weevil larva was recorded. Many other very sus-
picious observations were made but no definite proofs found.

ANTS WHICH PREY UPON THE WEEVIL. 69

12. LEPIDOPTEROUS LARVZ WHICH ARE INCIDENTALLY PREDATORY
UPON THE BOLL WEEVIL.

Alabama argillacea Wiibner. The cotton leaf caterpillar is distinctly
an enemy of the boll weevil and of considerable importance. When
it defoliates a cotton field a month or more before the frosts it often
destroys immature weevils in the cotton squares and cuts off the entire
food supply of the adult weevils remaining. These weevils may be
able to suspend their activities and begin hibernation but it is well
known that weevils entering hibernation early in the fall can seldom
survive a long hard winter, or live until cotton is up in the spring.
Those that can not hibernate either die of starvation or rise in flight
to seek cotton elsewhere and may perish in the effort. It is presumed
that a very high percentage of flying weevils fails to find cotton.

The leaf worm is attacked by 18 predatory bugs, 16 predatory
beetles, 6 predatory wasps, and the following ants: Dorymyrmex
pyramicus flavus McCook, Forelius maccooki Emery, Solenopsis
geminata Fabricius (these three ants are enemies of the boll weevil)
and Monomorium carbonarium Smith. Ten hymenopterous parasites
and one hyperparasite are known, and in addition the leaf worm is
attacked by a predatory fly and by two parasitic flies.

13. ANTS WHICH PREY UPON THE BOLL WEEVIL.

HYMENOPTERA. DORYLIDA.

Eciton (Acamatus) commutatum Emery. This ant was taken by
Mr. C. R. Jones at Beeville, Tex., attacking the boll-weevil larvee in
squares. Dr. W. M. Wheeler states that it is commonly parasitized
by a round worm of the genus Mermis.

PONERIDZ.

Ectatomma tuberculatum Olivier. The ‘‘kelep,” or so-called Guate-
malan ant, is a native of Mexico and Central America. Like all other
ponerids it is slow in action. The winters have proven too severe
for any of the imported colonies. The rate of development is so
slow and the movements of the adults are so sluggish that little
could be hoped for from this species even if it could become accli-
mated in this country.

MYRMICID2.

Oremastogaster lineolata (Say) var. clara Mayr. This ant is also an
enemy of the boll weevil, having been recorded attacking immature
stages at Dallas, Tex., by Dr. W. E. Hinds. It has frequently been
seen in the rearing cage carrying off insect prey. ‘The species lives

70 INSECT ENEMIES OF THE BOLL WEEVIL.

in hollow stems, sticks, and galls and is commonly seen at the necta-
ries of cotton or attending aphides, membracids, etc. Prof. F. E.
Brooks has recorded this ant as an enemy of Heltothis obsoleta, the
cotton bollworm.

Solenopsis geminata Fabricius. The “fire ant” (fig. 16) is very
common in Texas cotton fields, where it is always an enemy of the
boll weevil, as well as of the cotton bollworm (Heliothis obsoleta)
and the cotton leaf worm (Alabama argillacea). In Louisiana,
Arkansas, and Mississippi it is very seldom seen in cotton fields,
except in southern Louisiana, where unfortunately it is in danger of
extermination by the Argentine ant, Jridomyrmex humilis Mayr.
This species divides credit for the greater part of the ant control of
the boll weevil with the other species of Solenopsis, two species of
Monomorium, and with the various spe-
cies of Pheidole. Its nests are placed in
the cotton fields, generally near the base
of the plants, and from these the foragers
go out in all directions in search of food.
The workers have learned to detect the
presence of the boll weevil in the squares
and in a short time can effect an entrance
into the weevil cell from which they either
draw the weevil bodily or convey it in
parts to their nests. This ant is some-
times found on the plant, but most com-
monly it does its work on the ground.
The species is parasitized by (Pseudac-
Fic. 16.—The “fire ant” (Solenopsis 0) Plastophora crawfordi Coquillett at

geminata), an enemy of the boll Dallas. Tex.

weevil: Worker. Enlarged. (From i ° oe

unter and Ends) Solenopsis molesta Say (debilis Mayr).

This minute ant was taken in the act of

attacking a boll-weevil larva by Mr. Cushman at McAlester, Okla.
This species and the next are so similar in appearance that they
may be easily confused. Prof. F. E. Brooks has recorded it as an
enemy of Craponius inzxqualis.

Solenopsis texcana Emery. This minute ant is a common enemy
of the boll weevil in Texas, Louisiana, and Mississippi. The entrance
holes are very minute, but sometimes the ants enter the squares in
great numbers. On October 31, 1907, at Thornton, Tex., Mr.
Cushman found 85 individuals attacking a weevil larva in a single
square. It is mentioned in the investigation records as attacking
the weevil at Alexandria and Monroe, La., and Cuero, Lampasas, and
Llano, Tex. It is also recorded as an enemy of Heliothis obsoleta.

Monomorium minimum Buckley. This common house ant (fig. 17)
is avery valuable enemy of the boll weevil and is common in cotton

ANTS WHICH PREY UPON THE WEEVIL. 71

fields. It is recorded in the Dallas collection as attacking the boll
weevil at Llano, Lampasas, Albany, Henrietta, Arlington, and Dallas,
Tex., Ruston, La., and Roxie and Port Gibson, Miss. The species
has been taken attacking the immature stages of Trichobaris com-
pacta, Anthonomus albopilosus, and Anthonomus fulvus. It generally
attacks these weevils as well as the boll weevil on the plant, entering
the infested bud or square in search of its food.

Monomorium pharaonis L. This cosmopolitan house ant (fig. 18)
is another of the most important boll-weevil enemies, being very

Fig. 17.—The little black ant (Monomorium minimum), an enemy of the boll weevil: a, Fe-
male; 6, same with wings; c, male; d, workers; e, pupa; f, larva; g, egg of worker.
Enlarged. (From Marlatt.)

abundant in the cotton fields of certain sections. It is represented
in the Dallas collection as attacking the boll weevil at Victoria, Tex. ;
Fosters, Ruston, and Monroe, La., and Camden, Ark. It also
attacks the weevil on the plant. In southern Louisiana it is being
exterminated by the Argentine ant (/ridomyrmex humilis).

Pheidole sp., near flavens. At Arlington, Tex., August 31, 1908,
Mr. Cushman found abundant evidence of the control of the boll
weevil by this species. It attacks the weevil larve both on the
plant and on the ground.

(7 INSECT ENEMIES OF THE BOLL WEEVIL.

Pheidole crassicornis Emery. At Lampasas, Tex., September 23,
1908, Mr. Cushman found this ant a very abundant enemy of the
boll weevil.

DOLICHODERIDA,

Forelius maccooki Forel. At Beeville, Tex., August 13, 1906, Mr.
C. R. Jones found a high mortality of the boll weevil due to this
species. Dr. Wheeler has recorded the fact that this ant prefers
bare, dry ground for its nests. The species also attacks Alabama
argillacea and Heliothis obsoleta. On September 7, 1908, at Dallas,
Tex., Mr. F. C. Bishopp took specimens in the act of attack, and
September 21, 1908, Mr. Cushman took others at Llano, Tex., attack-
ing the weevil.

Dorymyrmez pyramicus Roger, the ‘‘lion ant,’”’ protects solitary
tree cotton from the boll weevil in Cuba (Schwarz, 1905).

Fig. 18.—The little red ant (Monomorium pharaonis),an enemy of the boll weevil:
a, Female; b, worker. Enlarged. (From Riley.)

Dorymyrmex pyramicus (Roger) var. flavus McCook. This com-
mon ant of the cotton fields has only once been taken as an enemy
of the boll weevil, namely at Texarkana, Tex., by Mr. R. C. Howell,
but its abundance would make it a very important species if it
should develop a fondness for weevil larve. It is an enemy of
Alabama argillacea and Heliothis obsoleta.

Iridomyrmex analis André. Specimens of this ant were found
attacking the boll weevil by Dr. W. E. Hinds. This species is nor-
mally a honey ant, but occasionally takes insect food. It is very
common in cotton fields, especially in Louisiana.

Iridomyrmex humilis Mayr. The much-feared Argentine ant has
been taken attacking the boll weevil. It is, however, a friend to
the weevil because it exterminates Solenopsis geminata, Monomorwum
pharaonis, and Iridomyrmex analis (Foster, 1908).

BIOLOGY OF THE COHOSTS. 73

FORMICIDA.

Formica fusca (Linneeus) subpolita (Mayr) perpilosa Wheeler. This
species of ant is normally a honey feeder, but it is recorded by Rangel
(Rangel, 1901c) as a predator on adult boll weevils in Mexico.

Formica pallidi-fulva Watreille. A single instance of this species
cutting its way into a square infested by a boll weevil was observed
by Mr. Hood at Ashdown, Ark., September 2, 1908.

Prenolepis imparis Say. A single instance of this species cutting
its way into a square infested by a boll weevil was observed by Mr.
Hood at Ashdown, Ark., September 2, 1908.

14. BIOLOGY OF THE COHOSTS OF THE BOLL-WEEVIL PARASITES.

The biologies of the parasites concerned in the boll-weevil complex
have already been discussed. It now remains to consider the native
weevils which have already or may later enter into the complex of
cohosts of the boll-weevil parasites. Many of these weevils are
native to the territory already occupied by the weevil, while others
will become important as new territory is added. Other families of
Coleoptera and even other orders of insects may later be found to be
of more or less importance as cohosts of boll-weevil parasites. The
late Dr. William H. Ashmead stated that Microbracon mellitor had
been reared from many Coleoptera, while Cerambycobius cyaniceps
bred in cerambycids and other beetles. It is important also to note
the record of Cerambycobius cyaniceps from Languria. Our own
observations have been confined to the Coleoptera of the families
Lariide, Anthribide, and Curculionide.

PHYTOPHAGA. LARIIDZE.

(Bruchus)' Laria sallei Sharp. This bruchid is characteristic of
the Gulf Coast prairie of Texas. It breeds in the pods of huisache
(Vachellia farnesiana), is a continuous breeder, and is generally highly
parasitized by Urosigalphus bruchi, Cerambycobius bruchivorus, CER-
AMBYCOBIUS CYANICEPS”; CERAMBYCOBIUS CUSHMANI, LARIOPHAGUS
TEXANUS, EURYTOMA TYLODERMATIS, Horismenus sp., and several
other undetermined parasites.

Larva exigua Horn. ‘This bruchid is apparently Austroriparian and
Carolinian. Its principal food plant is Amorpha jruticosa, in the seed

1 The generic name Bruchus was first used by Geoffroy in i762. Only one species is admissible in our
code of nomenclature and this is CerambyxfurLinneus, which is also the type of Ptinus Linnzeus 1767,
The genus Laria was described by Scopoli in 1763 and the type thereof has been designated as salicis
Scopoli, a synonym of Dermestes pisorum (pisi) Linneeus.

Linnzeus’s conception of Bruchus dates from 1767 and the type thereof was designated by Latreille
(1810) as Dermestes pisorum Linnzus. Hence we see that Bruchus Linnzeus (1758) is preoccupied by
Geoffroy (1752) and an isogenotypic synonym of Laria Scopoli (1763).

Although the genus has been subdivided into several genera, our American species have not been
studied with regard to such subdivision and it is hence best to consider all as in the genus Laria,
sensu latiore.

2 The names of boll-weevil parasites are printed in small capitals; others in italics.

74 INSECT ENEMIES OF THE BOLL WEEVIL.

pods of which it breeds prolifically. It is a continuous breeder and
is highly parasitized by Cerambycobius brevicaudus, CERAMBYCOBIUS
cryANiceps, Horismenus sp., Heterospilus prosopidis, Eurytoma sp.,
MICRODONTOMERUS ANTHONOMI, CATOLACCUS INCERTUS, and several
other species.

Larva obtecta Say. The common bean weevil is known to be para-
sitized by CERAMBYCOBIUS CYANICEPS and Bruchobius laticollis.

Larva compressicornis Schaeffer. This bruchid, which breeds in
the pods of Acuan illinoensis, is parasitized by CERAMBYCOBIUS CY-
ANICEPS and /eterospilus prosopidis.

Laria ochracea Schaeffer. This bruchid, which breeds in the pods
of Vicia sp., is parasitized by CERAMBYCOBIUS CYANICEPS, C. CUSH-
MANI, Lurytoma sp., and Heterospilus prosopidis.

Spermophagus robiniz Schaeffer. This bruchid is very common in
the pods of the honey locust (Gleditsia triacanthos), and the water
locust (Gleditsia aquatica), both of which are trees belonging to the
humid Austral zones. It is parasitized by Heterospilus bruchi, Crr-
AMBYCOBIUS CYANICEPS, EURYTOMA TYLODERMATIS, and Urosigalphus

bruchi.
RHYNCHOPHORA. ANTHRIBID®.

Brachytarsus alternatus Say. This beetle probably breeds under
many different circumstances. The only records are from a fungus
gall on Ipomea pandurata, and from the stems of Elymus virginicus
and Sideranthus rubiginosus. It apparently belongs to the humid
Austral zones. It is parasitized by MicRoDONTOMERUS ANTHONOMI
and a Bracon. ;

Arecerus fasciculatus DeGeer. This very widely distributed
Lower Austral insect (see fig. 19), known commonly as the coffee-
bean weevil,
breeds in stored
vegetable prod-
ucts, in the seed
of Theobroma
cacao, in the
berry of the coffee
tree (Coffea ara-
bica), in diseased
cotton bolls, in
seed pods of
Cassia occident-

Fic. 19.—The coffee-bean weevil (Arzcerus fasciculatus), a cohost of boll- :
weevil parasites: a, Larva; b, adult; c, pupa. Enlarged. (From Chit- qligs and C. ob-

tenden. ine.
ioe tusifolia, in seeds

of Indigofera tinctoria, in green and decaying fruit of Melia azedarach,
in green and dry cornstalks, and in dry acarian galls on [pomea

BIOLOGY OF THE COHOSTS. 15

lacunosa. In the Melia berries it is parasitized by CeraMBYCOBIUS
CUSHMANI, HURYTOMA TYLODERMATIS, and PEDICULOIDES sp.

CURCULIONID. APIONINAE.

Apion segnipes Say in Cracca virginiana is parasitized by Eury-
TOMA TYLODERMATIS.

Apion decoloratum Smith. Dr. Chittenden records this weevil as
breeding in Meibomia paniculata and parasitized by CaroLaccus
INCERTUS.

Apion griseum Smith. Dr. Chittenden records this weevil as
breeding in Phaseolus retusus, P. wrightii, P. polystachyus, and
Strophostyles pauciflora, and parasitized by CATOLACCUS INCERTUS.

Apion nigrum Smith. Breeds in buds of Robinia pseudacacia and
is parasitized by CATOLACCUS INCERTUS.

Apion rostrum Say in pods of Baptisia is parasitized by CERAMBY-
COBIUS CYANICEPS.

CLEONIN.

Tnxus musculus Say. This weevil is known both from the Lower
Sonoran and Austroriparian zones. It breeds in the stems of Poly-
gonum pennsylvamcum, P. portoricense, and P.
punctatum, making an oblong gall or swelling.
It is parasitized by EuRYTOMA TYLODERMATIS,
CERAMBYCOBIUS CYANICEPS, Neocatolaccus
tyloderme, Glyptomorpha rugator, G. novitus,
and Horismenus lixivorus.

Lizus scrobicollis Boheman. This weevil (fig.
20) is probably confined mainly to the moist
Austral zones. It breeds abundantly in the
stems of Ambrosia trifida, A. artemisizxfolia,
A. psilostachya, and Helianthus spp. It is

quite highly parasitized by Ptinobius magnisicus,

oar cee apart EURYTOMA TYLODERMATIS, CERAMBYCOBIUS

cohost of boll-weevil para- CYANICEPS, Glyptomorpha rugator, G.mavaritus,

The tot eaten " G. liai, Vipio belfragei, Microdus simillimus,

. and Horismenus lizivorus. Mr. 'Townsend has

described Lizophaga parva from a specimen reared from this weevil
at Dallas, Tex., August 15, 1907.

ERIRRHININA.

Smicronyz tychoides LeConte. This weevil breeds in stem galls of
various species of Cuscuta. It is parasitized by MicRoBRACON MEL-
LiToR and Hutrichosoma albipes.

76 INSECT ENEMIES OF THE BOLL WEEVIL.

Desmoris scapalis LeConte. This weevil (fig. 21) occurs mainly
on the black prairie in Texas and breeds in the heads of Sideranthus
rubiginosus. It is parasitized by MicROBRACON MELLITOR.

ANTHONOMINZ.

Macrorhoptus sphexralciz Pierce. This weevil was found breeding
in stems of Sphxralcea angustifolia. It is the host of Huryroma
TYLODERMATIS.

Tachypterellus quadrigibbus Say. This fruit weevil breeds in the
seed of apple, pear, Crategus oxyacantha, and Crategus mollis. \t is
known to us to be parasitized by CERAMBYCOBIUS CYANICEPS and
CATOLACCUS HUNTERI.

Smicraulaz tuberculatus Pierce. This species breeds in the stems
of mistletoe (Phoradendron flavescens) throughout Texas, and evi-
dence of its work has been observed in Louisiana and Mississippi. It
is parasitized by EURYTOMA TYLO-
DERMATIS, CERAMBYCOBIUS CYANI-
CEPS, CATOLACCUS HUNTERI, and
MicROBRACON MELLITOR.

Anthonomus fulvus eConte.
This weevil breeds in the larger
buds of Callirrhoe involucrata and
C. digitata. It is a characteristic
woodland and meadow insect in
Oklahomaand Texas. Theknown
parasites are CATOLACCUS INCER-

Fic. 21.—The ironweed weevil (Desmoris sca. TUS and MIcROBRACON MELLITOR.

palis), a cohost of boll-weevil parasites. En- ; Nat eien
AeRee. | (itvots Bintan erie Hida) Anthonomus signatus Say. The

strawberry weevil is mainly char-
acteristic of the humid Austral zones, and it breeds in the buds of
strawberry, blackberry, dewberry, raspberry, Rubus villosus, Poten-
tilla canadensis, and Cercis canadensis. It is parasitized by Micro-
bracon anthonomi, Calyptus tibiator, CATOLACCUS HUNTERI, C. INCER-
rus, and ©. anthonomi. The two latter species were described from
this weevil.

Anthonomus albopilosus Dietz. This little Texas weevil breeds in
the capsules of Croton capitatus, C. engelmanni, and C. texense. It
is known to us to be parasitized by MicROBRACON MELLITOR, CATO-
LACCUS HUNTERI, C. INCERTUS, and CERAMBYCOBIUS CYANICEPS.

Anthonomus nigrinus Boheman. ‘This species is eastern in habitat
and breeds in the buds of Solanum carolinense, and the potato (S.
tuberosum). It is the host of Hntedon lithocolletidis, Eriglyptus
robustus, CATOLACCUS INCERTUs, and C. anthonomi.

BIOLOGY OF THE COHOSTS. 3 TI

Anthonomus xneolus Dietz. This Texas weevil breeds commonly
in fungus galls on the leaves and in the buds of Solanum eleagnifolium
and S. torreyi and also in the buds of S. rostratum. It is parasitized
by CaToLaccus HUNTERI and a Kurytoma.

Anthonomus eugenit Cano (xneotinctus Champion). The pepper
weevil (fig. 22) breeds in most of the cultivated and wild peppers
and may be considered a serious pest. It is parasitized by CaToLac-
CUS HUNTERI, MicROBRACON MELLITOR, and PEDICULOIDES VENTRI-
COSUS.

Anthonomus squamosus LeConte. This is a weevil typical of the
gypsum prairie of the Lower Sonoran Zone, although occurring less
abundantly in the western edge of the moist Austral zones. It
breeds in the flower heads of Grindelia squarrosa nuda, G. inuloides,
and perhaps also on other Grindelias and Helianthi. It is known
to us to be parasitized by MicroBracon
MELLITOR, CATOLACCUS HUNTERI, and Eury-
TOMA TYLODERMATIS.

Anthonomus nebulosus LeConte. This wee-
vil breeds in the buds of Crateegus in Louisi-
ana and Arkansas. It is parasitized by Cato-
LACCUS HUNTERI and Sigalphus sp.

Anthonomus heterothece Pierce. This small
weevil breeds in the flower heads of Hetero-
theca subaaillaris and probably other asteroid
flowers. It is parasitized by CaToLaccus
HUNTERI and EUuRYTOMA TYLODERMATIS. Fic. 22—The pepper weevil
Previous records by the senior author on — (Ariienomus tugent), & conest

) Oll-weevll parasites, n
Anthonomus disjunctus LeConte all refer to larged. (From Hunter and
this weevil. aie

Anthonomus aphanostephi Pierce. This weevil breeds in the heads
of Aphanostephus skirrobasis, and is parasitized by CaToLaccus
INCERTUS.

TYCHIINA.

Tychius sordidus LeConte. This Austroriparian weevil breeds in
the pods of Baptisia bracteata and B. leucantha. It is parasitized
by CERAMBYCOBIUS CYANICEPS.

CRYPTORHYNCHINA.

Chaleodermus ezneus Boheman, the common cowpea weevil (fig. 23),
is abundantly parasitized by EnnyomMaA GLosBosa, and is likewise a
host of Ennyomma clistoides and StIGALPHUS CURCULIONIS.

Conotrachelus afinis Boheman. This weevil breeds in hickory nuts
and is parasitized by My1lopHAsiA NEA and SIGALPHUS CURCULIONIS.

78 INSECT ENEMIES OF THE BOLL WEEVIL.

Contrachelus juglandis LeConte. This is the walnut weevil, which
is also parasitized by My1topuasia NEA, Cholomyia inxequipes, Meta-
dexia basalis, and SIGALPHUS CURCULIONIS.

Conotrachelus elegans Say. This weevil breeds abundantly in
the petioles of hickory, the galls of Phylloxera devastatriz on pecan,
in pecan nuts, in leaf
rolls on hickory, and
finally in the roots
of Amaranthus retro-
flecus. It is fre-
quently parasitized
by MYIoPHASIA NEA
and SIGALPHUS CUR-
CULIONIS, and occa-
sionally by Cholomyra

imequipes.
Fic. 23.—The cowpea weevil (Chaicodermus xneus), a cohost of
boll-weevil parasites. Enlarged. (From Chittenden.) Conotrachelus nen-

uphar Herbst. The
common plum curculio (fig. 24) breeds in the pulp of drupes and
pomes. The larve are parasitized by Cholomyra inequipes, SIGAL-
PHUS CURCULIONIS, MICROBRACON MELLITOR, and Porizon conotracheli,
and the eggs by Anaphes conotracheli.

Conotrachelus naso Le-
Conte. The common
acorn weevil is para-
sitized by SIGALPHUS
CURCULIONIS.

Tyloderma foveolatum
Say. Thiscommon wee-
vil breeds prolifically in
the stems of Onagra bien-
mis and Epilobium. It
is highly parasitized by
Neocatolaccus tyloderm, Fre. 24—The plum cureulio (Conotrachelus nenuphar), a cohost

CERAMBYCOBIUS CYAN- of boll-weevil parasites: a, Larva; b, adult; c, pupa. Much
: enlarged. (From Chittenden.)

ICEPS, EURYTOMA TyY-
LODERMATIS, MICROBRACON MELLITOR, SIGALPHUS CURCULIONIS, and
Urosigalphus sp. nov.

Gersteeckeria nobilis LeConte (Acalles). The common prickly-pear
weevil is parasitized by CaToLaccus HUNTERI and by several other
species.

BIOLOGY OF THE COHOSTS. 719
CEUTORHYNCHIN®.

Auleutes tenuipes LeConte. This weevil breeds in the anthers of
buds of Galpinsia hartwegi on the Texas black prairie at least. It is
attacked by Carotaccus 1ncerTus, Microbracon sp., Eutrichosoma
albipes, and possibly by Catolaccus migroxnea.

Craponius wnequalis Say. This weevil breeds in the fruit of the
grape. It is parasitized by MicROBRACON MELLITOR and Stiboscopus
brooksi.

Rhinoncus pyrrhopus Boheman. 'This weevil breeds in the stems
of Polygonum and is parasitized by CERAMBYCOBIUS CYANICEPS.

Ceutorhynchus n. sp. This weevil breeds in the crown of Selenia
aurea and is parasitized by CATOLACCUS INCERTUS.

BARINE.

Baris cuneipennis Casey. This weevil breeds in the roots of
Helenwum tenurfolium and is parasitized by CaTOLACCUS INCERTUS.

Orthoris crotch LeConte. This
Lower Sonoran weevil breeds in the
seed pods of Mentzelia nuda. It is
parasitized very highly by Microbracon
nuperus, EURYTOMA TYLODERMATIS,
and a species of Tetrastichus.

Trichobaris texana LeConte. This
species breeds very abundantly in
stems of Solanum rostratum, and is
hence more or less a Lower Austral
insect. Its parasites are CERAMBYCO-
BIUS CYANICEPS, EURYTOMA TYLODER-
MATIS, MICROBRACON sp., and SIGAL-
PHUS CURCULIONIS, Fic. 25.—The potato-stalk weevil (Tricho-

Trichobaris trinotata Say. The po- baris trinotata), a cohost of boll-weevil
tato stalk weevil (fig. 25) breeds in saceaineee a ice lori dak Nee
the stems of many Solanacez, includ- to show larva and pupa in situ. a,b, ¢,
° . Five times natural size; d, natural size.
ing Solanum carolinense, S. melongena (ero Chittenden.)
(egg plant), S. rostratum, S. tuberosum
(potato), Datura stramonium, D. tatula, Physalis longifolia, P. philadel-
phica, P. lanceolata, P. heterophylla, and P. virginiana ambigua. Tt is
known to be parasitized by SIGALPHUS CURCULIONIS and EuryToMA
TYLODERMATIS. .

Trichobaris compacta Casey. This weevil breeds in the pods of
Datura stramonium and is also recorded as breeding in Datura mete-
loides. It is parasitized by CERAMBYCOBIUS CYANICEPS, MYIOPHASIA

NEA, and PEDICULOIDES VENTRICOSUS.

80 INSECT ENEMIES OF THE BOLL WEEVIL.

Ampelogly pter sesostris LeConte. The grapevine gall weevil is para-
sitized by My1ropuasta NEA, Neocatolaccus tylodermx, and Calyptus
tibvator.

Zygobaris xanthoxyli Pierce. This weevil is abundant in the berries
of NXanthorylum clava-herculis. It is parasitized by CaroLaccus
HUNTERI and SIGALPHUS CURCULIONIS.

BALANININA.

Balaninus nasicus Say. This weevil breeds in acorns. It is para-
sitized by Myiopuasta #NEA and possibly by Trichacis rufipes.

CALANDRINE.

Calandra oryza Linneus. The cosmopolitan rice and corn
weevil (fig. 26) breeds in acorns of several species of oak, in galls of
Phylloxera devastatrix on Hicoria pecan, in
old cotton bolls, and in all kinds of stand-
ing and stored grain. It is parasitized by
Meraporus calandre, M. vandiner, M. uti-
bilis, M. requisitus, and CATOLACCUS IN-
cERTUS. Other parasites have been re-

: ported abroad.
aie yea), 2 cohest of baltweevy «10» A LIST OF THE HOST PLANTS OF THE

parasites. Enlarged. (From COHOST WEEVILS.

pees In order to show more plainly the num-
ber and variety of plants whose presence around the cotton field,
if infested by their typical weevils, would influence the parasite
control of the boll weevil, the following list 1s presented, using the
classification of Britton (1901):

Plant. Infested by—

Triticum sativum (wheat)...-...----------
THT OES COR ICIOTS ae Tee ey

Zea mais (corn)

OPA AUINGNEICO) = 22.228 Nee ele eer ere
JUG (AMS EMIOG (WELL sees = eels ware ee
Hicoria sp. (hickory)
Hicorva alba (hickory)
Hicoria pecan (pecan)

Quercus spp

Phoradendron flavescens
Polygonum pennsylvanicum
Polygonum portoricense.........-2.--+------

Polygonum punctatum.....-..-..---------
AMNATONIRUS THO PCLUS < ec ase se eae

Calandra oryza I..
Anthribus alternatus Say.
f Arecerus fasciculatus DeG.
| Calandra oryza L.
Calandra oryza.
Conotrachelus 9 uglandis Lec.
Conotrachelus affinis Boh.
Conotrachelus elegans Say.
Conotrachelus elegans.
Balaninus spp.
Conotrachelus naso Lec.
Calandra oryza L.
Smicraulax tuberculatus Pierce.
Tivus musculus Say.
Lixvus musculus.
Taxus musculus.

(Fninemrs pyrrhopus Boh.
Conotrachelus elegans Say.

HOST PLANTS OF COHOST WEEVILS.

81

Plant.

Infested by—

NLL TRL 21 RE Ce NS ee
Rubus villosus (blackberry)........--.-----
Rubus trivialis (dewberry)........---------
Rubus occidentalis (raspberry)... .---------
Fragaria virginiana (strawberry)...--.------
Potentilla tanddens 8.2 <220222-2-222-2-+- 2-3
EUTUS COMMAS (HEAT). 22 ene awn8 Gee owe
HIMES MOLUS (ADDO) sac 2% S221 viste a sane 6 ete

Crakeous Mois: (MEW \ordsd 2 onc oS. See

CYOLLOUS OXYOCUNINE: 02. se ede ose ee elen otc
PE OTESA ip UE) ane see emai. eee ec 2
Amygdalis persica (peach)........--.-------
Amygdalis persica (nectarine)............---
Amygdalis armeniaca (apricot)..........--.--
Vachellia farnesiana (huisache) ...-...-.-..-
ACUON THATOCNEIS ene 2 acest Sele a. Were t's =

Strombocarpus (screw-bean).......--------
Prosopis glandulosa (mesquite). .......----
Cercis canadensis (redbud)......-.-----------
GRE OULUST OL Oe circ can bates sek ndob awd
WE QSSUAOCCIOCN UAL os at nina Ponts Ries day
Gleditsia aquatica (water locust).......-....
Gleditsia triacanthos (locust).........-------
Vigna unguiculata (cowpea). ......--------
OPUS ONIOICOL Manse vo a HON Sat naesed eae
BUD MO TOUCR ING OS 225 boc uba dos oe byt Ps
BYU TWISTS AY (1/0 0 ae eae a ee
ANDO OU UIA GON nen ee = ee
TNO Ofer UNGIONIA...- notes nas 2 soeee ens ac
CROCCO ONTO NO wee eee
EL OUWUIG PSCUUUCR Lhe s23 oso. ee Me eee oo
EA ts ete ae Bin ree Pee ann amy cl
MCLOOTING DOMICULOMEs s8 c8* a88Se fae a dn ens
Phaseolus polystachyus........-.-+------++--
Pes ULL SM OLNSILG Screg ia de Seed cas ie hin gig th
PENOSCOUNS WGN 22 Pinas 2232 Satges nes ts
Phaseolus vulgaris (bean).........----------
PROSCOLUS WULOONIS «oe aso oeOeie nook cess
Strophostylus pauciflora. ........-.--------
Xanthorylum clava-herculis....-.-..2-+-+----
Melia azedarach (China tree).......-.-.---.-
COP OLOTE COURS oon Siac. cos ee 5 wee eae
CTC MONO NON sac eonse one ese etla eee
COOLIO EROS Cony vaig cia ceca ted. ay ls sens a

Callrnoe digutana. 2 Bosse oo eek wed ca dn
Callirrhoe involucrate... cc. = 222 on cc oon ne
Spheralcea angustifolia...........-...-------

Gossypium hirsutum (cotton). ........-----

TARA ELL (tS ee a eae re
Opin (prickly pear) .22 feces 2h Poe e
Opuntia engelmanni.....--....-...202--20-
BU DUTOMLLIIO Bieta ow a= ace Siar See eek araed
CMU Oasys cncceg 2 no, 2 so whe otis elec htt «
OO Uren ais otis 8 ieee Rn oan Bo

16844°—Bull. 100—12——-6

Ceutorhynchus sp.
Anthonomus signatus Say.
Anthonomus signatus.
Anthonomus signatus.
Anthonomus signatits.
Anthonomus signatus.

Tachy pterellus quadrigibbus Say.

Tachy pterellus quadrigibbus.
{ Tachypterellus quadrigibbus.
\ Anthonomus nebulosus Lec.

Tachypterellus quadrigibbus Say.

Conotrachelus nenuphar Ubst.

Conotrachelus nenuphar.

Conotrachelus nenuphar.
Conotrachelus nenuphar.
(Bruchus) Laria sallai Sharp.
Laria bisignata Horn.

Laria prosopis Lec.

Laria prosopis.

Anthonomus signatus Say.
Arxcerus faseiculatus DeG.
Arexcerus fasciculatis.
Spermophagus robinix Schon.
Spermophagus robiniz.
Chalcodermus xneus Boh.

Tychius sordidus Lec.

Tychins sordidus.

Apion rostrum Say.

Laria evigua Horn.

Arexcerus fasciculatus DeG.
Apion segnipes Say.

Apion nigrum Sm.

Laria ochracea Schaeft.
Apion decoloratum Sm.
Apion griseum Sm.

Apion griseum.

Apion griseum.

Chalcodermus seneus Boh.
Laria obtecta Say.

Apion griseum Sm.
Zygobaris xanthoryli Pierce.
Arexcerus fasciculatus Dietz.
Anthonomus albopilosus Dietz.
Anthonomus albo pilosus.
Anthonomus albopilosus.
ae peloglypter sesostris Lec.

Craponius inequalis Say.
Anthonomus fulvus Lec.
Anthonomus fulvus.

Macrorhoptus sphxralcix Pierce.

Anthonomus grandis Boh.
Arexcerus fasciculatus DeG.
Chalcodermus xneus Boh.

| Calandra oryza L.

Orthoris crotchit Lec.
Gerstxckeria nobilis Lec.
Gerstxckeria nobilis.
Tyloderma foveolatum Say.
Languria sp.

Tyloderma foveolatum Say.

82 INSECT ENEMIES OF THE BOLL WEEVIL.

Plant.

Infested by—

COUIUIS IO MOMWEO cence see scnew seat. 5k
LVOTUO NOCUNOSG <cictan =e oo Pate eee ote Ue

PNUSU MAL ONCCOOMe acne Een es. ae nee
PHYUSOUUS VOTO 1 OU mercies sae Aces eee
Phiysatis piiladel piven. <acxsee. S85 oe ence
Physalis virginiana ambigua........--..----

Solanum carolinense.....-.------.----------|

MOLAMIUU CICUONIOUME ic awcee 2. oa eae
Solanum heterodocvum........-.-------------
Solanum melongena (egg plant)............--
DOLGMUNUTOSILOLUM = 2.8 eae ee. ee
Solanum rostratum..........-.------------

MOLIWITIE LOFICY Use ae acc a ne eee ee

Solanum tuberosum (potato)..............---
Capsicum annuum (pepper) .--.-----
DOkUra SPOON oo nen oe teak oie a ee

DC TEE ULEIU NO i atc aloe ee ati nN oe ie rea
Ambrosia artemisixfolia......-.......--+---
Ambrosia psilostachya..........-...-----+--
ATRUTORUG WU ie. ate Rs ae See ae
CRINGE ANU ONES. aba 2ceenaedi aes ene see
Grindelia squarrosa nuda........-----------
Heterotheca subawillaris..........2-.2.-------
STOW BOLIC OVI tx oe See Bee ee eee Satan ee te
DUUCPONENUS TUN QUNOS8 2 aes eee Be eos eens
Sideranthus rubiginosus.....------+---2-----
Aphanostephus skirrobasts.......--.---------
Helianthus spp. (sunflower)..............--

Auleutes tenuipes Lec.
Arexcerus fasciculatus DeG.
Brachytarsus alternatus Say.
Trichobaris trinotata Say.
Trichobaris trinotata.
Trichobaris trinotata.
Trichobaris trinotata.
Trichobaris trinotata.

f Trichobaris trinotata.

\ Anthonomus nigrinus Boh.
Anthonomus xneolus Dietz.
Trichobaris texana Lec.
Trichobaris trinotata Say.
Trichobaris tecana Lec.
Anthonomus xneolus Dietz.

a nthonomus xneolus.
Trichobaris texana Lec.

4 nthonomus nigrinus Boh.
Trichobaris trinotata Say.
Anthonomus eugenii Cano.

\Tetobons trinotata Say.
Trichobaris compacta Casey.
Trichobaris trinotata Say.
Lizus scrobicollts Boh.
Lixus scrobicollis.

Lizvus scrobicollis.
Anthonomus squamosus Lec.
Anthonomus squamosus.

Anthonomus heterothece Pierce.
Anthonomus aphanostephi Pierce.

Desmoris scapalis Lec.
Brachytarsus alternatus Say.

Anthonomus aphanostephi Pierce.

Lizus scrobicollis Boh.
Baris cunetpennis Casey.

16. A SUMMARY OF THE MORE IMPORTANT BIOLOGICAL FACTS.

1. The boll weevil has 54 enemies, including parasites and predators.

2. These enemies are native to other insects which are to be found
in the vicinity of cotton fields.

3. The interrelationships of the boll weevil and its parasites with
surrounding insects are very complicated.

4, The parasites are sometimes found in great numbers.

5. The cotton plant, by its production of nectar, furnishes a very
powerful attraction for parasites and predatory insects.

6. The development of the boll-weevil parasites is as rapid as that
of the boll weevil.

7. Most of the parasite species are well distributed.

8. The parasite species attack other hosts in the spring and have
a generation before the boll weevil is ready for them.

9. New species of parasites are becoming adapted to the weevil
each year.

ECONOMIC PRINCIPLES INVOLVED. . 83

10. Other cotton insects, by their ravages upon the food of the
weevil, sometimes reduce the numbers of the boll weevil itself.

11. Much valuable work is done by the ants, which are present in
many fields.

PART III. THE ECONOMIC APPLICATION.

The economic application of parasitic control to the boll-weevil
problem is dependent upon accurate knowledge of a multitude of
conditions. The preceding two parts of this bulletin have been
devoted to a statement of the many phases of the parasite situation.
It must be understood at the beginning of this part that we consider
the utilization of parasites and other insects inimical to the boll
weevil as intimately connected with good agriculture. The boll-
weevil problem, from a parasite standpoint, is entirely different
from any other parasite problem ever studied. In other cases such
means as introductions from foreign countries may be utilized. In
the present case the main problem is to devise such agricultural
practices as will increase the effectiveness of the parasites already
present.

In order to facilitate the treatment of the economic methods to be
suggested, this part is also divided into sections, which are as follows:

1. The economic principles involved.

2. Interpretation of parasite statistics.

3. Interpretation of the biological complex.

. How to profit by existing conditions.

. How to plan for the greatest possible control.
. Propagation and artificial introductions.

. Objectionable practices.

. The economic significance of the investigation.

CONT OS Ot He

1. THE ECONOMIC PRINCIPLES INVOLVED.

The attempt at utilization of insect enemies in economic ento-
mology is now receiving so much attention that the authors will
set down the principles which appear to have been the foundation of
the work they have done.

1. Insects in a state of nature are more or less completely held in
check by natural agencies, in which other insects frequently figure
as of direct or indirect importance. Many insects are controlled
almost entirely by their insect enemies. No insect is without its
natural checks.

2. The relationships between an insect and its enemies can not
be expressed by a simple ratio, nor are they in any way invariable.
The agencies operating for and against the welfare of a given species
are so many and of such inconstant magnitude, due to the activities

84 INSECT ENEMIES OF THE BOLL WEEVIL.

of other agencies, that the effects of one or two agencies of control
with known strength can not be estimated, because of the many
other agencies either unknown or of unknown strength.

3. When an injurious insect escapes from its natural surroundings
to a region where conditions are favorable for enormous reproduction,
it may become a pest, but it is never absolutely free of natural checks.
Anthonomus grandis has never been free of its checks although it
escaped those of its native home. These agencies of insect control
are inherent to all countries: An insect parasite is as likely to escape
its original surroundings as a phytophagous insect.

4. When an insect finds in its vicinity a variety of food closely
related to its native host, and that food is more succulent or more
abundant, there is a possibility that sooner or later the more inviting
food will become the normal food. This possibility becomes stronger
when the original food supply fails, if the species is to be continued.
Not only phytophagous but entomophagous insects have frequently
been proven to have thus changed their food habits—whether from
preference or necessity it is not known. Leptinotarsa decemlineata
(the Colorado potato beetle) is an excellent example of this change of
habit among phytophagous insects. All of the boll-weevil parasites
are examples of parasites which have adjusted their habits in the
presence of their original hosts.

5. A crisis in the history of a species occurs whenever the food
supply fails. The species may either disperse in search of food, as
the boll weevil does each autumn, or it may hibernate or estivate,
or it may select a new host, or the species may perish. All these
results occur in nature. All of these alternatives may be chosen by
different individuals of the same species. It is safe to assume that
when a species is found to have many hosts that it has undergone
many crises and that the resultant species is a highly developed and
adaptable form. A species most limited in food habit is most liable
to restriction or extinction and consequently of a lower type than
one able to meet any emergency.

6. When a desirable parasite species is known to be adaptable to
various hosts, a crisis may be artificially superinduced by the timely
elimination of the favorite hosts, thus forcing the species to attack
the most predominant near-by related host in the vicinity, or it may
be taken to an entirely remote or foreign locality and placed near a
field containing many insects closely related to its original host,
which it may learn to thrive upon.

7. The species most available for utilization are those most adapt-
able to changing environments, or those having the most hosts in
the given locality. These other hosts will serve as nurseries for
parasites,

INTERPRETATION OF PARASITE STATISTICS. 85

8. Certain parasites with more or less established habits require
that their hosts be in certain habitual locations (for example, Neocato-
laccus requires stem-dwelling hosts), and in like manner there are
conditions which can be made more favorable for parasite attack
through cultivation or through plant selection. Furthermore, since
parasites require different conditions, it is desirable to alter the
existing conditions so as to make them favorable for as many species
as possible. In the case of insects extending their range over many
different climates it should be the aim to introduce parasites best
adapted to the prevalent conditions.

2. INTERPRETATION OF PARASITE STATISTICS.

From the great mass of parasite statistics given in Part I a number
of important facts need to be considered.

Parasitic and predatory attack is strongest from August until frost
time. Hence it may be presumed that whatever artificial propaga-
tion is to be done will be most profitable when conducted during this
period, provided it does not interfere with early fall destruction of
stalks, the fundamental cultural remedy against the boll weevil.

The greatest control of the boll weevil by insects and also by
all agencies is in hanging squares. As has been stated in Part I
(sec. 3), the hanging squares are a result of a diagonal absciss layer,
which causes the drying square to fail in separating itself completely
from the plant. These squares die on the plant and afford a very
favorable position for parasitic attacks upon the weevils within.
The statistics show that insect control in fallen squares is greatest in
the moist States of Louisiana and Mississippi. This is undoubtedly
due to some of the new parasites which are accustomed to attacking
woodland weevils and other insects characteristic of this humid
region. The insect control in hanging squares is the greatest in the
comparatively dry States of Texas and Oklahoma. These dry States
also have a higher combined natural control in the fallen squares
than in the hanging squares, largely because the climatic conditions
cause a higher mortality of weevil stages in squares lying on the
heated surface of the ground. On the contrary, the humid States
have a higher mortality from both climatic and insect agencies in
hanging squares than in fallen. Furthermore, it has been proven, in
Part I (sec. 4), that an increase in the amount of hanging squares
will increase the total control. Having these facts in mind, the
obvious conclusion is that it will be desirable to have varieties of
cotton which have this tendency best developed. Among the varie-
ties which are now known to retain their squares are the cluster
varieties, including the Rublee.

86 INSECT ENEMIES OF THE BOLL WEEVIL.

The figures show that parasitism becomes very high under favor-
able conditions and also that agriculture modifies the insect control.
Obviously therefore those agricultural methods which will favor the
highest insect control must be sought. These methods, as now
known, will be dealt with more fully in a following section.

It was feared for a long time that the parasites of the weevil would
be held in control by the warm climatic conditions which affect the
boll weevil. This isnot so. We have found abundant proofs of the
fact that a temperature which will kill the boll-weevil larva will not
kill the egg or small parasite larva in the same cell, and that the
parasites can develop to maturity on the dried remains of the weevil.
The temperature fatal to the boll weevil is 123° F., a temperature
frequently reached on a hot burning soil. We have found in several
years that a low temperature which will kill the boll-weevil larva is
also not fatal to the parasites, for in November, 1907, when 97 per
cent of all the boll-weevil stages were frozen, no evidence whatever
could be found of mortality among the parasites. The minimum
fatal temperature of the boll weevil is 12° F.

3. INTERPRETATION OF THE BIOLOGICAL COMPLEX.

The complicated biological factors which have been noted in Part II
have been summarized briefly in section 16 of that part (p. 82).
The interpretation of these facts has been suggested in a number of
places throughout the second part. Hence only a few words are
necessary at this point.

The fact that surrounding each cotton field there are numerous
plants harboring weevils and their parasites is of extreme importance
in this problem. ‘These parasites are generally capable of attacking
the boll weevil under conditions of necessity or alternative choice.
The aim is therefore to find all the methods by which these parasites
may be forced to leave their native hosts and attack the boll weevil.
In fact, the entire second part has been devoted to giving these facts
in order to bring out this single point.

4. HOW TO PROFIT BY EXISTING CONDITIONS.
COLLECTION OF COTTON SQUARES IN SCREENED CAGES,

As has just been pointed out, there are conditions around the cotton
fields which are potential of a considerable increase in the parasitic
control of the boil weevil. Probably no other method will yield
better results than the gathering of the cotton squares which are
infested and placing them in wire-screen cages of 16 or 18 mesh to
the inch and placing these cages in selected parts of the cotton
fields. This method is not new in entomological practice. It has

HOW TO PROFIT BY EXISTING CONDITIONS. 87

been used with great value in the freeing of apple orchards in Europe
from the apple-bud weevil (Anthonomus pomorum). The boll weevils
can not pass through a 16-mesh or 18-mesh wire screen, while the
parasites can do so, and therefore the release of these enemies will
be constantly increasing the proportion of parasites against the
weevils. Even if a 14-mesh wire screen is used, only a small pro-
portion of the weevils can escape through it and some gain is effected
by the release of the parasites. In order to demonstrate numerically
just how this would happen, three hypotheses are presented. In the
first case squares are collected and put in a 16-mesh wire cage, and
in the second case squares are collected and put in a 14-mesh wire
cage, and in the third case no squares are collected. The average per-
centage of control which follows as a result easily demonstrates the
advantage which will be almost immediately gained. .

It has been contended and proven that many weevils escape
through the ordinary wire screen.

I.—Given 10,000 developing stages in a 1-acre field.

(A) Collect squares containing 50 per cent of the stages and place in 16-mesh

SLR ETE LOE OUR CLA c gee paar ee en AR AE or Vier arene a ae ee 5, 000
PUOTING oa ractistiNis ey (CE CONG scenes are ol eremias owe alee SS So Soo 250
Risen west kull40 yomcent 2. .12.- seater pe ne eo ae 2, 000
GGL ee Men he Gee ae eet SD Ne Ba ak eee ws 2, 250

IBS ELCY6 ed Aes 9 are Da oy ene ae RE ei tae Pea 2,750

There escape through 16-mesh screen—

Ree COM Wer Ves ocnccs 2s ate sea eG wea eo tahoes Doaate eee man 275
DUSNEr CONE PARARITCE. Scat. coueoamacy anced ce ecce ee ena matenaeak Sees 225
(B) There remain in the field squares containing 50 per cent.....-.-..-..---- 5, 000
Normal mortality as above, 45 per Cent. 2.2.2.2 cose be Sees seeks ese 2, 250
BESSY GC es eer et rg Se at We ay rate an cA gh Bi EA 2,700
Nome Weewdis CoCADEU IRON! COVES... cecesceer aaa sse ane Sak oe oie secoeeec$ 275
TOA Weevils ab COG OL CONCTAMON occ sed ccs oon Sd eke dicagn en ome” 3, 025
PUTAS IUCS gr COLCU mete wre ete ae ee acs oye ah eee Aer bah = eal cs cha er 250
Pera eeecra Doh WOml CAMGa oo 222s shoes me oly Sao ele 225
ATacILes PYesOmy IMEC eras. cotace ste stamina te oo 3 tee pee. se 475
There is | parasite to every 6.3 weevils.
IT.— Given conditions as above, squares in 14-mesh screened cage.
(a) ei roml, collected equates Dreette. a. 6 22.5565 sence ee. Pec eedl sek ote us cas 2,750
There escape through 14-mesh screen—
RU per Cent WeCVillc waren. os sc ees deen ems ene ood seeks totes 1, 100
aul Oy sfc hic tate cs Cae aeeeee oe, Seen te ani oe ernie the eee ae ee bee eer ae 250
(CED ye Veh areca aay, s8(25 U6 Lege ee scresesee eee ene ete Aen eae 2, 750
BUCH Oca LO MI CAPCS. 2 coke hea i asteroe ms Serpe ta Se Se cS oe eta ae Oe 1, 100

Total weevilssat end! Of PENSTALION. Soames ome cee cer ee oe emcees = 3, 850

88 INSECT ENEMIES OF THE BOLL WEEVIL.

Nee linrets ccc hac(s eee ee ee OO ee Ae gs ee he 250
PRrasited GSCaPCds st Severe telsee eee vy cee eee Se eee are 250
IP ArASTGSR RUIN ATC LC crosses ayer ee ee ee 500

There is 1 parasite to every 7.7 weevils.

ITI.—Given 10,000 developing stages in a 1-acre field.

Nowsquiares'are collected... .+.s=2 S422 100 250 cee eu ebae ee aseemesa oes eee ee 10, 000
Norma léparasitism, 5-per Cems. 2 42 cesta ee ees ee ee 500 ,
Ante andehest all 40 per cents sac 120s tone enws se toes ee ec oe eee es 4,000
MORI 35 cca of Jl +.0's esl eae ganna eee See oneness ee en 4, 500
Breed a cictise eoces Se bys Do ete ete we eparate = See tree ape ee ee 5, 500

Parasites reared, 500.
There is 1 parasite to every 11 weevils.

SUMMARY.
Squares collected and
placed in—
Squares not
collected.

14-mesh 16-mesh

wire cage. wire cage.
Woe vile monraiites oc cmt ane og, der a oe oe eee 5, 500 3, 850 3, 025
Parasites remain.......... ee ee ee 500 500 475
Ratio of parasites to weevils............----------- i Dean I ey eat L2G.3

ELIMINATION OF COHOSTS.

Another practice of undoubted value in bringing about a higher
percentage of parasitism upon the boll weevil is the elimination of
the cohosts of the boll-weevil parasites at proper times. To show
what has been done in this line, the case of the Dallas farm in 1907
may be cited. On July 19 of that year a very large hedge of weeds,
Ambrosia trifida, infested by Lizus scrobicollis was cut. These weeds
were along the fence adjoining a part of the cotton field which had
been under close observation for parasites throughout 1906 and the
spring of 1907. In 1906 there was not found in any plat on this
farm a higher parasitism than 2 per cent by Hurytoma tylodermatis in
hanging squares. Eurytoma was very numerous in the Ambrosia
weeds next to this field, but did not appear to attack the weevil in
large numbers. Before the weeds were cut in 1907 the two plats
nearest these weeds averaged 26.76 per cent and 16.79 per cent
parasitism by Eurytoma. On August 17, about a month after these
weeds were cut, the two plats just mentioned had, respectively, 37.50
per cent and 26.66 per cent parasitism by Eurytoma. This striking
gain adjoining the weeds was not reflected by parts of the field farther
removed.

HOW TO PROFIT BY EXISTING CONDITIONS. 89

EARLY DESTRUCTION OF THE CO’TON STALKS.

There can be little doubt that the early destruction of the cotton
stalks, in addition to depriving the boll weevil of its food plant, will
_also cause the parasites to seek a series of hosts which can carry them
through the winter period. In order to prove that fall destruction
does not have an injurious effect upon parasite control, we would cite
the discussion of the Victoria fields, in which various methods of fall
destruction were carried out, as discussed in Part I, section 6. Asa
further proof the famous Olivia fall-destruction experiments may be
considered.

On October 1 to 10, 1906, all of the cotton plants in over 400 acres,
constituting the entire Olivia cotton community in Calhoun County,
Tex., were cut and burned under the direction of Mr. J. D. Mitchell.
According to the rearing records in our possession, the parasites
developing in this cotton would all be mature before November 10,
and if they hibernated, would have to do so as adults. No other
cotton existed within 12 miles, as the community is completely iso-
lated by water and marshland.

Cotton was planted about March 15, 1907. On April 15 no boll-
weevil work could be found, but on May 7 a single weevil was found
after a careful examination of eight fields. On the same date at Six
Mile settlement, across the bay near Port Lavaca, there was consider-
able infestation. If the parasites hibernated as adults they would be
dead long before the middle of June. If they could have hibernated
as immature stages they would have matured by March 15, and under
normal conditions three generations would have passed by June 15.
The infestation was still very sight in July. It must be argued,
therefore, that any boll-weevil parasites must be breeding on some
other weevil, if they did not perish.

On August 22, 1907, Mr. Mitchell found parasites with weevil-
infested squares on a field in the opposite part of the community to
that in which he first found the weevil infestation. The obvious
inference is that a rotation of hosts occurred during the period of the
boll weevil’s absence.

Having planned the cropping system, it is also best to prepare the
fields early for cotton and plant as early as possible. Of course, most
of the reasons for early planting of cotton are well known and the
practice is very common, but in this connection it must be said that
such early planting has the actual advantage of enabling the para-
sites to start early.

Care must be given to the choice of the cotton variety which is to
be used. Frequent recommendations have been made of varieties
with light foliage, early maturing fruit, short nodes, and determinate
growth. All of these qualities are favorable to parasite control,

90 INSECT ENEMIES OF THE BOLL WEEVIL.

especially since such plants afford much more sunlight on the ground.
The ants and also the parasites prefer much more to attack the
squares which are dried out than moist squares. It seems that they
can more readily penetrate the linings of the square. In addition to
these qualities of the cotton variety, the use of a variety with at
least a moderate amount of nectar is also advised. The reason for
this has been explained in preceding paragraphs. Finally, the tend-
ency of plants to retain the squares must be again mentioned. If a
variety can furnish the desired qualities of early producing, produc-
tiveness, and quality of lint, as well as a diagonal absciss layer on the
square, that variety should be chosen above others.

If at all possible, it is advisable to plant the rows far apart or on
the check-row system, in order to give the necessary amount of sun-
light. The cultivations to follow this should be with the purpose
of obtaining a dust mulch, for with such a mulch the surface of the
soil may be heated to a much higher degree than by deep and lumpy
cultivation, and the control of the boll weevil will thus be greatly
increased, through the drying effect upon fallen squares.

5. HOW TO PLAN FOR THE GREATEST POSSIBLE CONTROL.

As it has been proven that many agricultural processes are favor-
able to the development and attack of parasites and enemies, there
can be no question but that it is desirable to plan to obtain the great-
est amount of this beneficial aid.

There are a few plants which have no objectionable qualities in
themselves which might with good reason be planted adjacent to the
cotton fields in order to induce the attack of weevils which act as
hosts of the boll-weevil parasites. For instance, the presence of a
hedge of blackberries or dewberries along the fence means the pre-
sence of Anthonomus signatus, the blackberry bud weevil, with its
numerous parasites, all of which attack the boll weevil. The para-
sites would be able to carry on a generation in the spring before the
boll weevils were breeding and would mature in plenty of time to
attack the first developing stages of the boll weevils.

It would seem advisable to plant a hedge of the flowering shrub
Amorpha fruticosa, which is the host plant of Laria exigua. This
little wevil is very abundantly parasitized.

In planning the cropping system there can be no possible harm
in arranging to have a forage or hay crop adjacent to the cotton
field. In case a forage crop is used, cowpeas with the ever-present
cowpea pod weevil would undoubtedly bring about the presence
of several important parasites. The early removal of the cowpeas
for fodder would force the parasites to attack the boll weevil. In
the case of a hay field, the process of haying and subsequent curing

PROPAGATION AND ARTIFICIAL INTRODUCTIONS. 91

would enable the parasites present in the various weeds to escape
and attack the most abundant host, namely, the boll weevil.

If, with all these precautions, the boll weevils are very numerous
in the field, and the expense is not too great, much can be gained by
picking the squares and placing them in cages, as has been described
in a previous section.

Finally, at the proper season for haying, the actual methods of
cutting and preparing the hay will without doubt furnish still greater
control to the weevil. Some time in September, if not before, whether
haying is carried on or not, there should be a thorough cutting of all
weeds around the cotton field in order to force the parasites to the
boll weevil and also to get rid of favorable hibernation quarters for
the boll weevil.

6. PROPAGATION AND ARTIFICIAL INTRODUCTIONS.

The propagation of parasites under artificial conditions and their
introduction are attended with a great amount of labor and expense
and have many technical difficulties. The simplest form of propaga-
tion is the collection of infested squares at one locality and the ship-
ment of them to another locality, where they are placed in the field
to await results. There are good reasons for attempting thus to
introduce parasites. It has been found by very close observations
that the parasites are not evenly distributed, but that each species
has a more or less definitely defined geographical region. This is
no doubt due to the distribution of the normal host weevils. The
purposes of introduction are to take these parasites from their native
localities and place them in geographical regions in which they do
not at present exist. Definite proofs that results can be obtained
in this manner were to be had at Dallas on the experimental farm in
1906 and also in 1907. The 1906 experiment has been fully described
in the first report on the parasites of the boll weevil (Pierce, 1908a).
In 1907 a similar experiment was tried by the release of large numbers
of adult parasites. These parasites were carried to a field in small
screen cages containing foliage, so that the parasites might not become
overheated. The cages were opened in the shade, and the parasites
allowed to fly out in any direction which they pleased. While many
species of parasites were released in this manner, they did not all
show the results that were expected, but the release of Catolaccus
incertus in a given part of the field accomplished an increase in the
control in hanging squares by this species. In two other parts of the
field Microbracon mellitor was released, and it also showed good gains.
As Microbracon was released on this farm both in 1906 and 1907, it may
be useful to compare the percentages of parasitism at various periods.
In August, 1906, this species furnished 8.5 per cent parasitism in hang-

92 INSECT ENEMIES OF THE BOLL WEEVIL.

ing squares; in September, 1906, this had risen to 10.2 per cent; in
‘July, 1907, the parasitism by this species was 35.2 per cent, and in
August, 1907, it had risen to 39.8 per cent.

At Shreveport, La., in 1908, many specimens of Catolaccus incertus
and Microbracon mellitor were released. Table XXII gives an idea of
the results and shows the expected increase by Catolaccus in both
hanging and fallen squares and by Microbracon in hanging squares.

TABLE XXII.—Lxperiment in artificial introduction of Catoloceus incertus and
Microbracon mellitor, Shreveport, La., 1908.

Percentage of mortality. Gain in mortality.
Class of forms. Plat. Date. Total

Total. | Pata- | Cato- | Micro-| 72° | Cato- | Micro-

“| sites. | laccus. |bracon. Yt a laccus. | bracon.

Per cent.|Per ceni.|Per cent.

Fallen squares. .... Release...| Oct. 5 | .36.44 5.93 4,23 HST QI) Sos wicechscoee | crereteee ore | eee eee
1D OM tee eee aeeUO.o. sou2 Oct. 28 37.96 15. 74 10.80 2.16 165 150 33

DO Rae Check: ...... Oct. 5 | 40.00] 10.50 5. 55 BuilO: | sists See Selioboas ose a eeseeees
DOs a2 22s0 2a BeOS see Oct. 28 42.33 16. 00 8.00 5. 00 52 44 35
Hanging squares...) Release Oct. 5] 47.15 9.90 4.39 Bs 20) | cio $s sl are ese Sere memes
(cjpRi-ey area Se (6 (omer Oct. 29 64. 86 37. 84 10. 81 18.91 282 148 477

RELEASE CAGES.

In order to obtain satisfactory results from the release of infested
material, it is necessary to place the material in cages from which
the injurious weevils can not escape but which will still allow the
parasites egress. This principle has been explained in other sections.
There is also another important consideration in the construction of
the cages. When a large amount of material such as this is collected
in a small space it furnishes great inducements to attack by colonies
of ants. The only way that the material can be protected from total
destruction by ants is the isolation of the cage on legs by the use of
“inverted cups”? containing oil, or by greasing the legs in some
manner.

TRANSFER OF ANT COLONIES.

Since the work of ants is always very favorable to control, means
should be devised of increasing their numbers in the cotton field.
The dust-mulch method of cultivation is very favorable to the ants
in that it does not disturb their colonies after they have commenced
breeding. This is a very important matter to consider. The late
Mr. F. C. Pratt, in working with the horn fly (Lyperosia twritans
L.) discovered that fresh manure containing numerous fly larve
is very attractive to Solenopsis, and that these ants seem to trans-
fer their whole colony at times to the manure. Mr. Wilmon Newell,
in connection with the Argentine ant investigations, at a later
date, found that he could trap immense colonies of the Argentine

OBJECTIONABLE PRACTICES. 93

ant Uridomyrmex humilis) by means of boxes containing manure.
These observations are very suggestive, for they point out the possti-
bility that colonies of ants can be obtained by placing fresh manure
in boxes near ant colonies. When sufficient numbers have entered,
they may be boxed up for removal to a place desired. In this manner
great colonies could be transferred bodily for considerable distances.

lord

(. OBJECTIONABLE PRACTICES.

There are several practices which are quite objectionable from the
standpoint of encouraging the parasites and most of which have
also been found objectionable from purely cultural standpoints.
When the cotton is planted closely on moist soil its growth is mainly
vegetative and consequently immense stalks may have very little
fruit. Agriculturists have always pointed out that large cotton
plants need plenty of room in order to produce fruit. Field examina-
tions to determing the mortality of the boll weevil from various causes
have always shown that the parasitism is greatest in the portions of a
field where the foliage is lightest. A notable example was found at
Natchez, Miss., where in a single field the growth was very irregular.
One spot seems to have been used for feeding cattle and was very
fertile. On this spot the cotton grew 6 or 8 feet tall and the ground
was densely shaded. Here the mortality of the weevil was very low,
and there was scarcely any control by insects. One hundred feet
from this was a thin piece of ground where the cotton plants were
barely 2 feet high, but they were loaded with bolls and showed a
much higher percentage of mortality, especially by insect enemies.
An actual count of the number of bolls in the two parts of the field was
greatly in favor of.the smaller plants.

Late planting has been proven objectionable from almost every
standpoint from which it has been viewed. Under existing circum-
stances there are no valid arguments for late planting. From the
standpoint of control by parasites late planting simply delays the
attack of parasitic enemies and reduces the amount of control in the
fall at a critical time.

It is believed that the use of varieties which always tend to drop
their squares is objectionable if varieties with the opposite tendency
can be found with the same qualities of production.

The practice of picking squares and then burning them can not be
condemned too strongly. The planters are by this practice almost
nullifying the good work that they do by picking the squares. They
are doing nothing more or less than destroying their best friends
when they burn these squares. This may be proven by an hypothesis
similar to those presented (p. 87) in demonstrating the value of collect-
ing the infested squares.

94 INSECT ENEMIES OF THE BOLL WEEVIL.

Given 10,000 developing stages of the boll weevil in a 1-acre field.

(A) Collect and burn squares containing 50 per cent of the stages............. 5, 000

This destroys all parasites as well as weevils.
(B) There remain in the field squares containing 50 per cent of the stages

PICSEU basse cas eiie sen ose oe ce be meiminieleln oe ele Seteiecis Sete a =e aewielsemiesiee 5, 000
Nonna) parasvusnl oO Per COW hs. <<. seem cece secre ea ate eee 250
Ants and bear kill 40 per Contsss csc avec cece owen ee erm eee seers 2, 000
Montaltin case: stocachskcwctan cmt oe sme eres operat aye a ee ee 2, 250
Weevlls to breed ois ncc26 stat eeeon ate eae an edt eee eee 2, 750

Parasites present in field, 250.
There is 1 parasite to every 11 weevils.

This method undoubtedly greatly reduces the totai number of
weevils in the field, but, as can be readily seen, the proportion of
parasites to weevils is the same as if nothing had been done—namely,
1 to 11. It was shown that by placing the squares in 16-mesh wire
cages the proportion would be 1 to 6.3. Hence it appears that by the
caging method the planter leaves in his field a more active agency
than he had before to attack the many weevil stages he has undoubt-
edly missed, whereas by the burning method he has not in the least
improved his field conditions.

8. THE ECONOMIC SIGNIFICANCE OF THE INVESTIGATION.

In final summary the following points are emphasized:

I. The control of the boll weevil by vnsect enemies is sufficiently great
to give it a high rank in the struggle against the pest. A considerable
portion of the insect control would not be accomplished by any other
factor; hence it is by no means to be neglected.

The number of species of insects attacking the developing stages
is 49.

The control in any given place consists of the combined work of
several different species.

Places having the largest number of controlling insects have the
highest percentage of control.

In many places insect control is considerably greater than climatic
control or than any other class of factors.

The average insect control is 20 per cent of all immature stages or
two-fifths of the entire natural control.

The cotton leaf-worm is a valuable enemy of the boll weevil when
it defoliates the cotton after September 1, a date beyond which new
squares can not be expected to mature. It kills many weevils by
starvation, kills many others while consuming the squares, and
finally forces a premature hibernation which is generally fatal.

ECONOMIC SIGNIFICANCE OF INVESTIGATION. 95

Il. The amount of control due to the various factors at work in any
given place should be increased vf possible. Parasites can be introduced
into new fields.

In order to prevent serious injury to cotton, the mortality of the
weevil should be above 90 per cent. It has averaged over 57 per cent
for four years and has reached almost 100 per cent several times.

While climatic influences occasionally bring the control above 90
per cent, they can not be regulated or in any way directly utilized.

Although the insect enemies present at a given place may be
accomplishing the greatest amount of work possible, the fact remains
that if other species of enemies are introduced and become estab-
lished the control can be increased.

Since certain parasites attack the weevil preferably in dry locations
and others in wet locations, and since some prefer to attack the
infested forms on the plant, while others seek them on the ground,
it is possible to select the insect agencies so as to obtain the least
amount of lost or duplicated energy.

Ill. The parasites and predators which attack the boll weevil are
native insects, already present in a given territory before the weevil
arrwes.

The predators, especially ants, will attack almost any kind of
insect food. The parasites in nearly all cases are capable of attack-
ing almost any kind of weevil breeding in herbs above ground or in
fruits.

The parasites have proven their ability to adjust themselves to
the boll weevil by attacking it in its first generation in newly infested
territory in instances where the actual sources of the parasites were
demonstrable.

The weeds surrounding the cotton fields contain many weevils
which are harboring multitudes of available parasites. These para-
sites may be induced to attack the boll weevil by the timely elimina-
tion of their native hosts.

This leads to the recommendation that planters cut the weeds adjoin-
ing the cotton fields, along the roadsides, turn rows, and fences about the
time of the maturing of the crop.

It also leads to the recommendation that a field adjoining the cotton
be used as a pasture or hay field, and that this field be mowed early in
the fall. The usual haying will also bring about the same result—
namely, the elimination of other plants harboring weevils which
attract the parasites needed in the cotton patch.

It is advisable to have in the vicinity of the cotton field such plants
as the dewberry, Croton, Amorpha, cowpeas, ete., which contain other
hosts of the boll-weevil parasites.

96 INSECT ENEMIES OF THE BOLL WEEVIL.

IV. The cultural methods of controlling the cotton boll weevil are the
most favorable methods of cotton culture from the parasitic standpoint.

The tendency of the principal boll-weevil parasites to prefer light
and heat leads immediately to a long series of recommendations.

Heat on the ground is essential for the climatic control of the
weevil and also for parasitic control. Although the two factors
overlap, each accomplishes considerable independent control.

A heated condition of the ground may be accomplished by planting
the rows far apart, by check-row planting, by flat cultivation, or by
planting varieties which have short limbs, or shed their foliage early, or
have small leaves.

Fall destruction of the cotton plants cuts off the parasites from
breeding on the weevil but sends them to other hosts upon which
they can breed a winter generation, or pass hibernation, thus gaining
not only a generation on the weevil but providing for themselves
during the winter.

The early planting of cotton in the spring makes it possible for the
earliest parasites to attack the weevil.

V. The tendency to retain infested fruit, which is displayed by
certain varieties, is worth consideration.

The fact that many more parasites are reared in hanging squares than
in fallen squares makes it desirable in humid regions to have many of
the hanging squares in a field in order to serve as a nursery of parasites

for the weevils in the fallen squares.

Varieties which show an elongate diagonal connection between
the square and stem will tend to have an imperfect absciss layer
formed. Prominent in this class are the cluster boll varieties of
cotton. Jt is recommended that search be made for such a variety as
will retain its infested forms and at the same time fulfill the other require-
ments in the making of a good crop.

VI. Any step which will diminish the number of weevils and not
diminish the number of parasites in a field will of course increase the
percentage of parasites present. .

The most important step of this kind is the collection of infested squares
and placing them in cages with a screen through which the weevils can not
escape but the parasites can.

Ant colonies may be introduced into the fields in boxes of fresh
manure.

Tf squares are collected, they should not be burned, but should be placed
in screcned cages.

INSECT ENEMIES OF THE BOLL WEEVIL. 97

BIBLIOGRAPHY.

ALpRIcH, JOHN MERTON.
1905. Catalogue of North American Diptera. <(Smithsonian Misc. Coll., vol. 46,
no. 1444, pp. 426, 427.
ASHMEAD, WILLIAM Harris.
1896. Descriptions of new parasitic Hymenoptera, 1]. <Trans. Amer. Ent.
Soc., vol. 23, pp. 218-219.
1902a. A new Bruchophagus from Mexico. <Boletin de la Comision de Para-
sitologia, vol. 1, no. 9, pp. 404. (For Spanish translation see Herrera.)
Banks, NATHAN.
1904. A treatise on the Acarina or mites. <(Proc. U.S. Nat. Mus., vol. 28, no.
1382, pp. 74-76.
1906. A revision of the Tyroglyphide of the United States. <(U.S. Dept. Agr.,
Bur. Ent., Tech. Ser. 13, p. 17, Pl. IV. :
BARREDA, L. DE LA.
1904. El picudo del algodén. Salvacion de la riqueza de la frontera. <(Comision
de Parasitologia Agricola, Cir. 6, pp. 14-27.
CHITTENDEN, FraNK HuRLBUT.
1893a. The strawberry weevil. <U.S. Dept. Agr., Div. Ent., Ins. Life, vol. 5,
pp. 181-182.
18936. Observations on some hymenopterous parasites of Coleoptera. <U. S.
Dept. Agr., Div. Ent., Ins. Life, vol. 5, p. 250.
1895. The potato-bud weevil (Anthonomus nigrinus Boh.). <U.S8. Dept. Agr.,
Div. Ent., Ins. Life, vol. 7, pp. 351-352.
1897. The strawberry weevil (Anthonomus signatus Say). <U. 8. Dept. Agr.,
Div. Ent., Cir. 21, p. 4.
1899. Insects injurious to beans and peas. <(U. S. Dept. Agr., Yearbook, 1898,
: pp. 242, 245.
1902. The potato stalk weevil. <U.S. Dept. Agr., Div. Ent., Bul. 33, n.s., p.17.
1908. An injurious North American species of Apion, with notes on related
forms. <U.8. Dept. Agr., Bur. Ent., Bul. 64, Pt. IV, pp. 30-32.
Cook, OraTor FULLER.
1904a. Anant enemy of the cotton boll weevil. <U.S. Dept. Agr., report 78, pp. 7,
May 27.
1904b. Report on the habits of the kelep, or Guatemalan cotton-boll weevil ant.
<U.S. Dept. Agr., Bur. Ent., Bul. 49, 15-pp., August.
1905. The social organization and breeding habits of the cotton-protecting kelep
of Guatemala. <U.S. Dept. Agr., Bur. Ent., Tech. Ser. 10, pp. 55.
CoquimLLeTT, DANIEL WILLIAM.
1897. Revision of the Tachinide of America north of Mexico, a family of para-
sitic two-winged insects. <U.S. Dept. Agr., Div. Ent., Tech. Ser. 7,
pp. 50, 51.
CRAWFORD, JAMES CHAMBERLAIN.
1907a. New hymenopterous parasites of Anthonomus grandis Boh. <Can. Ent.,
vol. 39, pp. 133, 134, April.
19076. New North American Hymenoptera. <Journ. N. Y. Ent. Soc., vol. 15,
no. 4, p. 179, December.
1908. Some new Chalcidoidea. <(Proc. Ent. Soc. Wash., vol. 9, pp. 157-160,
April 6.
1909a. New Chalcidoidea. <Proc. Ent. Soc. Wash., vol. 11, p. 52.
19096. ‘Two new species of the genus Tetrastichus. <(Proc. Ent. Soc. Wash., vol.
11, p. 150, October 5.

16844°—Bull. 100—12——7

98 INSECT ENEMIES OF THE BOLL WEEVIL.

Foster, F.
1908. The introduction of Iridomyrmex humilis (Mayr) into New Orleans,
<Journ. Econ. Ent., vol. 1, no. 5, pp. 289-293, October 5.

GirAutt, A. ARSENE.
1907. The lesser peach borer. <U. 8. Dept. Agr., Bur. Ent., Bul. 68, Pt. IV,
p. 40.

Contains an undoubtedly erroneous reference to (Bracon) Microbracon mellitor Say.

Herrera, Atronso L.
1902a. Sexto informe acerca del picudo del Algodon (Insanthonomus grandis
I. C. Cu.): Pequefia avispa pardsita del picudo. <(Boletin de la
Comisién de Parasitologia Agricola, vol. 1, no. 9, pp. 403-404.
This is a translation of Ashmead 1902b.
19026. Hormiga destructora del picudo. <Loc. cit., pp. 404-406.
This contains a translation of Wheeler, 1902.

Hinps, WARREN ELMER.
19072. An ant enemy of the cotton boll weevil. <U.S. Dept. Agr., Bur. Ent.,
Bul. 63, Pt. III, pp. 45-48, February 5.
19076. Some factors in the natural control of the Mexican cotton boll weevil.
<U.S. Dept. Agr., Bur. Ent., Bul. 74, December 14.

Hoop, CLARENCE ELLSWORTH.
1909. Types of cages found useful in parasite work. <Journ. Econ. Ent., vol. 2,
no. 2, pp. 121-124, April 15.

Howarp, LELAND OSSIAN.
1897. The Mexican cotton boll weevil (Anthonomus grandis Boheman). <U.S8.
Dept. Agr., Div. Ent., Cir. 18.

Hunter, Water Davin.
1907. Some recent studies of the Mexican cotton boll weevil. <(Yearbook
U.S. Dept. Agr., 1906, pp. 318-322.

Hunter, WatteR Davin, and WarREN Emer HInps.
1904. The Mexican cotton boll weevil. <U. 8. Dept. Agr., Div. Ent., Bul. 45,
pp. 104-110.

List of parasites and predators; adds as new records Sigalphus curculionis Fitch, Cato-

laceus incertus Ashmead, Urosigalphus (robustus Ashmead), Bracon (dorsator Say), and

Eurytoma tylodermatis Ashmead, as well as an entomophagous fungus, Aspergillus sp.

1905. The Mexican cotton boll weevil. <U.S. Dept. Agr., Bur. Ent., Bul. 51,
pp. 143-1590.

Hunter, Watrer Davin, Winmon Newe tt, and Wittiam Dwicrr Pierce.
1907. The insect enemies of the boll weevil. <Louisiana Crop Pest Comm.,
Cir. 20, December.

Ma.iy, FREDERICK WILLIAM.
1902. Report on the boll weevil. <(Public Printer, Austin, Tex., pp. 23-24,

Records (Bracon) Microbracon mellitor Say, Cerambycobius cyaniceps Ashmead, and
Eurytoma sp. from the boll weevil.

MorGan, ALFRED COOKMAN.
1907. A predatory bug reported as an enemy of the cotton boll weevil. <U.S.
Dept. Agr., Bur. Ent., Bul. 63, Pt. 1V, pp. 49-54, February 8.

NEWELL, Wiimon, and R. C. TREHEARNE.
1908. A new predaceous enemy of the cotton boll weevil. <Journ. Econ. Ent.,
vol. 1, no. 4, p. 244, August 15.

BIBLIOGRAPHY. 99

Pierce, Wim.1amM Dwicut.
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19076. On the biologies of the Rhynchophora of North America. <Ann. Rept.
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272, 274, 276, 278, 279, 282, 283, 285, 295, September.
1907c. Contributions to the knowledge of Rhynchophora. <Ent. News, vol. 18,
pp. 356-363 (October), 379-385 (November).
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Ent., Bul. 73, p. 63, January 21.
1908b. The economic bearing of recent studies of the parasites of the cotton boll
weevil. <Journ. Econ. Ent., vol. 1, no. 2, pp. 117-122, April 15.
1908c. Factors controlling parasitism with special reference to the cotton boll
weevil. <Journ. Econ. Ent., vol. 1, no. 5, pp. 315-323, October 15.
1908d. A list of parasites known to attack American Rhynchophora. <Journ.
Econ. Ent., vol. 1, no. 6, pp. 380-396, December 15.
1910. On some phases of parasitism displayed by insect enemies of weevils.
<Journ. Econ. Ent., vol. 3, pp. 451-488, December 15.
Pratr, FREDERICK CHARLES.
1907. Notes on the pepper weevil. <(U.S. Dept. Agr., Bur. Ent., Bul. 68, Pt. V,
p. 56, February 9.
RanGEL, A. F.
190la. Segundo informe acerca del picudo del algodon (Insanthonomus grandis
I. C. Cu.). <Boletin de la Comisién de Parasitologfa Agricola, vol. 1,
no. 0, pp: 171-176.
19016. Tercer informe acerca del picudo dei algodon. <Boletin de la Comisién
de Parasitologia Agricola, vol. 1, no. 6, pp. 197-206.
1901c. Cuarto informe acerca del picudo del algodon (Insanthonomus grandis
I. C. Cu.). <Boletin de la Comisién de Parasitologia Agricola, vol. 1,
no. 7, pp. 245-261.
Riney, CHARLES VALENTINE, and LBLAND OsstANn Howarp.
1890. Some of the bred parasitic Hymenoptera in the National Museum collec-
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TOWNSEND, CHARLES HENRY TYLER.
1895. Reports on the Mexican cotton boll weevil in Texas (Anthonomus grandis
Boh.). <U.S. Dept. Agr., Div. Ent., Ins. Life, vol. 7, pp. 295-309.
1908. The taxonomy of the muscoidean flies, including descriptions of new genera
and species. <(Smithsonian Misc. Coll., vol. 51, no. 1803, pp. 56-58, 86.
WHEELER, WILLIAM Morton.
1902. Formica fusca Linneeus, subsp. subpolita Mayr., var. perpilosa n. var.
<Boletin de la Comision de Parasitologia Agricola, vol. 1, no. 9, pp.
406-407. (For Spanish translation see Herrera.)

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