May IS, 1912.

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF ENTOMOLOGY— CIRCULAR No. 153.

L. O. HOWARD. Entomologist »nd Chid of Bureau.

THE COTTON WORM OR COTTON CATERPILLAR.

(Alabama argillacc a Ilulm.).

W. D. HUNTER,

In Charge of Southern Field Crop Insect Investigations.

—12

WASHINGTON : GOVERNMENT PRINTING OFFICE I 1012

B UREA U OF ENTOMOLOG Y.

L. O. Howard, Entomologist and Chief of Bureau.

C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief.

R. S. Clifton, Executive Assistant.

W. F. Tastet, Chief Clerk.

F. H. Chittenden, 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. Webster, in charge of cereal and forage insert investigations.

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

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

D. M. Rogers, in charge of preventing spread of moths, field ivork.
Rolla P. Currie, in charge of editorial work.

Mabel Colcord, in charge of library.

Southern Field Crop Insect Investigations.
W. D. Hunter, in charge.

F. C. Bishopp, A. H. Jennings, H. P. Wood, W. V. King, engaged in tick life-history
investigations.

W. D. Pierce, G. D. Smith, J. D. Mitchell, Harry Pinkus, B. R. Coad, R. W.

Moreland, engaged in cotton-boll weevil investigations.
A. C. Morgan, G. A. Runner, S. E. Crumb, D. C. Parman, engaged in tobacco insect

investigations.
T. E. Holloway, E. R. Barber, engaged in sugar-cane insect investigations.

E. A. McGregor, W. A. Thomas, engaged in red spider and other cotton insect
investigations.

J. L. Webb, engaged in rice insect investigations.

R. A. Cooley, D. L. Van Dine, A. F. Conradi, C. C. Krumbhaar, collaborators.

Circular No. 153. lsMU "' Mu > ». ''"^

United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.
L. O. HOWARD, Entomologist and Chief of Bureau.

THE COTTON WORM OK COTTON CATERPILLAR.

I abai ]illa> ea Eubn

By W. D. Hi mi k.
In Charge of Southern Field Crop Insect Investigations.

LNTR( »D1 i I H).\.

The cotton worm, or cotton caterpillar, also bul incorrectly called
the "army worm," has been known to cotton planters in the United
States since 1793. Before the invasion by the boll weevil it and the
bollworm were by all odds the most destructive cotton insects in
this country. During sonic seasons the damage by the caterpillar
began as early as June and occasionally the field's were completely
defoliated by the middle of July. The destructiveness of the insect
and the consternation caused among cotton planters by its ravages
are well described in an account published by Mr. Thomas Affleck of
Washington, Miss., in the American Agriculturist of September 9,
1846:

The caterpillar, cotton worm, cotton moth, or chenille i f the French Wesl Indies,
Guiana, etc., has utterly blighted the hopes of the cotton planter for the presenl year,
and produced most anxious fears for the future. I have hoard from the greater part,
of the rolton-Lirowiim region — the news is all alike — the worm has destroyed the crop.
I have no idea that any considerable portion of any State will escape. * * * The
present year the crop is unusually backward, at least four works later than usual.
We have but just commenced picking, usually beginning aboul the lasl week in July
or the first week inAugust. A.1 thismon rj field within this region of country,

say, south of Vicksburg, is stripped of everything but the stems, the larger branches,
and a few of the first bolls, already too hard for the worm powei Ema tii ition The
full-grown bolls noi yel become hard are completely eaten out, a circumstance 1 have
heard of but once before, in L825. The fields present a most melancholy appear-
looking from the bluff at Nat - the river to those tine plantation- Lack

of Vidalia, nothing i- to be "<-w bul the brown withered skeleton of the plant.

Until about ls?l no satisfactory methods of combating the cotton
caterpillar had been discovered. Many fallacious remedies, such as
attracting the moths to large tiro in the fields, were more or li -, in
ii-' hut the onl\ ones of even the slightest value were brushino the

2 THE COTTON WORM OR COTTON CATERPILLAR.

insects from the plants and preventing their invasion of the fields
by means of ditches. Early in the seventies the whole situation was
revolutionized by the discovery that the worms could be poisoned
quickly and economically by the use of Paris green or other arsenical
compounds. The practice of controlling the insect by these means
soon became universal in the South. Planters everywhere obtained
large supplies of poison each season exactly as other regular plan-
tation supplies were procured. As soon as the defoliation began the
poisons were applied. This checked the outbreak on the plantation
at the beginning, whereas without the use of the arsenicals it would
have spread over the entire cotton acreage. About the same time
certain changes in agriculture in the South also contributed in a
very decided manner to the reduction of the importance of the pest.
The large cotton fields began to be broken up into smaller fields
planted to a variety of crops. This system of diversification of
itself prevented such great increase in the number of the worms as
had taken place in previous years. These two facts together seemed
to indicate for many years that the cotton worm was no longer to
be feared as an important enemy of the cotton plant in the United
States.

For 21 years prior to 1911 the cotton worm had not been generally
abundant in the United States, although there was local damage
of some severity during different years in that period. Indeed the
passing of the insect had come to be considered such a settled fact
that the outbreak of 1911 was as surprising to the cotton planters
as to entomologists.

THE OUTBREAK OF 1911.

The outbreak of 1911 did not originate in the United States, but
in Central or South America. The moths flew northward very
early in the season and reached the neighborhood of Brownsville,
in Texas, by April. By the middle of June practically all of the
cotton fields in the vicinity of Brownsville that had not been pro-
tected by the use of poisons had become defoliated. The new gene-
rations of the insects flew northward and eastward during June and
July. During the latter month there appears also to have been
another invasion of the United States from South America. This
reinvasion took the moths into the South Atlantic States, where
they were soon found in very great numbers. They bred with great
rapidity and spread northward and westward. In August the west-
ern and eastern invasions coalesced, and within a few weeks the
insects were numerous in cotton fields throughout the belt.

Later in the season many of the moths which developed in the
cotton fields of the South flew northward, where they attracted con-
siderable attention. Millions of individuals were found in Wash-

I III. COTTON WORM OB COTTOK I \ I I KIM l.l.AK. 6

ington, D. ('.. between September L9 and October 29. On Sep-
tember 23 they were observed at Pittsburgh, Pa., and at Philadel-
phia on the same date. By September 25 they were found in great
numbers in New Haven, Conn., and on October 13 at Orono, Me.
Large numbers of specimens were observed in September al Mil-
waukee, Wis., and also al Ottawa, Canada.

Many of the moths which Hew northward were found upon fruits
of various kinds, which they punctured for the purpose of feeding.
Peaches, apples, grapes, and other fruits were at tucked in this
manner and fears arose among fruit growers that an important new-
pest had appeared.

POSSIBILITY OF W OUTBREAK l\ L912.

The cotton moth is of South American origin and does not survive
the winters in the United States, except when the temperatures are
above the normal or when individuals obtain unusual shelter.
Whether there will be an outbreak in L912 depends upon two con-
tingencies: First, whether any of the moths bred in t'.Hi succeeded
in surviving the winter in this country; and. second, whether a new
invasion from South America takes place.

Careful searches for the moth have been made in favorable locali-
ties in the southern part of the cotton bell during the past winter.
This investigation ha- extended from Brownsville, Tex., to South
Carolina. No live moths have been found. Mr. J. D. Mitchell, of
this bureau, placed chrysalides of the moth in rearing cages at Vic-
toria, Tex., in the fall of I'M i ;m ,| found that by the (Mid of January
they were all killed by the cold. These two fact- seem to indicate
thai all 'if the mot h- produced in the United States in 191] failed to
survive t be winter.

It is extremely difficult, however, to find the moth in hibernating
quarters, and the failure to find specimens is far from conclusive

proof that they do ii"1 e\i-l; but there i- another consideration
which bear- out the conclusion that the mot lis bred in this country
in 1011 were all killed during the winter. This b that the history of
the outbreaks of the cotton worm in the United State- show that the
insects were all killed during winters in which the temperature
below the normal. The winter of 1911-12 was abnormally cold
throughout I he cotton bi

Our conclusion, therefore, from all sources of information on which
dependence can be placed, is that the only fear of an outbreak during
l'.'l'- i- in a reinvasion of the United States from more southern
Localities. There i- "iir fad which seems t" indicate that there may
possibly be such a reinvasion. The chronology of the outbreaks of
the insect in this country from the earlier accounts shows a distinct

4 THE COTTON WORM OR COTTON CATERPILLAR.

tendency toward the recurrence of a series of two or three seasons of
abundance. Apparently the species reaches great numbers in South
America and remains abundant for several years, thus giving rise to
the consecutive swarms which have invaded the United States.
Since the region in which this occurrence takes place is far beyond
the influence of the recent cold weather in the United States, we may
suppose that the past history of the insect may be repeated and that
another invasion may be expected during 1912. This would seem to
be especially probable in case the temperatures of the spring months
should be above the normal.

We do not wish to be understood as predicting an outbreak during
the present season. The facts we have noted seem to indicate that
such may take place, but, on the whole, our position is that of giving
a warning rather than a prediction. In order to be on the safe side
it is advised that planters make the necessary preparations for fighting
the worm and that they begin operations at the earliest possible
moment.

THE COTTON CATERPILLAR AND THE BOLL WEEVIL.

In regions where the boll weevil occurs the cotton caterpillar is not
an unmixed evil. On the contrary, it generally acts as a decided
check against the boll weevil. The defoliation of the plants drives
many of the weevils out of the field and allows the sun to destroy
numerous immature stages in fallen squares on the ground. In fact,
where the defoliation is complete the boll weevil receives almost as
serious a setback as happens when the planter destroys the cotton
stalks in the fall. It must be noted, however, that there is a point
beyond which, even in boll-weevil regions, the cotton worm is not a
benefit to the crop. Where the defoliation begins early in the season
the plants may be prevented from maturing the bolls, and thus the
damage by the one insect is merely added to that of the other.

In regions where the boll weevil is abundant our advice is that planters
do not poison the cotton for the leaf worm, unless it becomes numerous
by the time the earliest bolls are about three-fourths grown. Where
the boll weevil is present but not in great numbers the poisoning
should be done at a relatively early date.

DESCRIPTION OF THE STAGES OF THE COTTON MOTH.

The egg. — The egg is light green in color and contrasts with the color
of the cotton leaf, so that it is easily detected by the practiced eve.
The eggs are generally placed on the underside of the leaves, never
in clusters. The female deposits about 500 eggs. The duration of the
c^ r g stage varies with the temperature, ranging from 3 days to more
than 20.

THE COTTON WORM OB COTTON CATERPILLAR. 5

Tin larva. The larvae <>f the cotton moth vary greatly in size and
coloration, but there are certain characteristic marks that enable one
to determine the species. (See fig. 1.) Early in the season the
larva- are yellowish-green and aol provided with conspicuous mark-
ings. A- a matter of fact, individuals without conspicuous markings
may he found in the cotton fields throughout the season. The form
generally seen, however, may he described as follows: Length about
11 inches, upper surface with a broad brownish or perfectly black
stripe. Down the center of the stripe is a line yellowish line and
similar lines hound the black area on either side. Each segmenl as
seen from above -how- four black dot-,, which, of course, are much
more conspicuous where the dorsal black stripe is less distinct. When
viewed from the side each segment shows four black dot- similar to
those on the dorsal surface, hut somewhat smaller in size.

The larvae feed by preference upon the cotton leaves. In eases
whore they are so abundant that the leaves are destroyed they feed
upon the squares and bolls and even the twigs. In t he case ><( attack
on bolls only the outer surface is devoured. On this account the
work of t he cot ton worm on bolls can be dist inguished from that of the
bollworm. The latter species gnaws a hole directly through the out-
side of the boll and feeds upon the interior.

Careful investigations have shown that the cotton worm feeds only
upon the cotton plant. In many cases where attempts were made to
breed it on other plants failure resulted. In one instance Mr. E. A-
Schwarz succeeded in causing a larva to develop tot he chrysalis stage
on morning-glory (Ipomata sp.). The chrysalis, however, was imper-
fect and failed to develop. The statement is frequently made that
the cotton caterpillar feeds upon pokeweed i Phytolacca sp.) and other
plants. Such reports are due to mistaking some other insects for the
cotton pest .

When the worms are numerous and a cotton held has been defo-
liated the\ frequently travel over the ground in great numbers in
search of food. This habit is the cause of the local use of the term
"army worm " for t he insect.

77/. chrysalis or pupa. The cotton caterpillar transforms to the
pupal stage on the cotton plant. Unlike t he bollworm, it never enters
the ground for this purpose. Usually it vpins a crude web, using a
portion df the cotton leaf for the purpose, hut in many cases no web
whatever is formed, and 1 he naked pupa hangs from t he col ton plant-

by means of a thread spun by the larva for t he purpose. (See lii, r . 1 .)
The duration of the pupal stage is from one to four weeks.

Tin adult. The adult, of the cotton worm is a moth, the wings of
which expand from LJ to il inches. See fig. ].) The general
color is brownish-yellow or tawny, in many specimens showing a
somewhat crimson hue. The most conspicuous feature of the upper

THE COTTON WORM OR COTTON CATERPILLAR.

Fig. 1.— The cotton worm (A labamaargillacca): ■ md work, (original.)

THE COTTON WORM OB COTTON I \ I ERPIL] \i;.

surface is a distincl black spol on the anterior wings jusl beyond
the middle and aboul one-third of the distance from the anterior to
the posterior margins. The fronl wings are also ornamented with a
number of transverse zigzag lines. The mosl conspicuous of these
arc one which crosses the anterior half of the wing immediately be-
yond the eye spol and another which extends from just behind the
eye spol to the posterior margin. In specimens which have become
rubbed these transverse markings are sometimes indiscernible.

The moth is nocturnal in its habits and has remarkable powers of
flight. This is show n l»\ its crossing t he < rulf of Mexico and reaching
localities iii the northern United States and Canada.

Unlike the great majority of moths the proboscis of this species is
strengthened, so thai it can puncture such substances as green pears
or apples, in [911 and various earlier years in which invasion- of
northern localities took place the damage to fruit in some cases was
considerable.

PASSING THE WIN IKK.

Whenever the cotton worm passes the winter in the United States
ii is in the adult stage. In this it is unlike the bollworm and other
species, which pass the winter in the pupal stage in the ground.

The question of whether the cotton moth hibernates normally in
the United States is one thai was discussed at greal length by entomol-
ogists and planters in former years. The early records and recent
observations all seem to hear out the belief thai the insect is in no
sense a incm her of the North American fauna, ami thai it can survive
the winter in this country only when the temperatures are favorable.
In fact, there is only one authentic record of the moths surviving the
winter in this country. This was the winter of 1881 82, which was
unusually mild. During thai winter live moths were found in the
vicinity of Archer, Fla., during every month of the winter up to March,
and young larvse were found a1 work on volunteer cotton at the end
of that month.

CONTROL.

The control of the cotton caterpillar is not at all difficult. The
methods to be described are simple and inexpensive. Consequently
there is no reason why every planter should not check the damage i
the beginning.

I>\ far the he- 1 method of control is by the use of powdered arsenate
of load. This substance has several decided advantages over any
other poison- that could be used. It does nol injure the foliage to any
extent whatever, and adheres to the leave- in -pile of considerable
rainfall. In both these respects it is much to !„■ preferred to Paris
green, which i- likely to injure the foliage and which does not adhere

to the leaves well except when mixed with Hour.

8 THE COTTO>~ WORM OB COTTON CATERPILLAR.

Powdered arsenate of lead should be applied at the rate of about
2 pounds per acre, more or less, depending upon the size of the cotton.
It is best to make the application when the leaves are moist with
dew. as is generally the case early in the morning. The less wind
there is the less will be the loss from the poison which drifts onto the
ground. Therefore a calm time should be selected.

The earlier the application of arsenicals can be made the better
it will be. The planter should not wait until extensive defoliation
has taken place. A watch should be kept upon the low moist areas,
where the worms invariably appear first. As soon as the destruction
of the leaves becomes evident in such places the poison should be
applied. By this means the outbreak may be checked, and the
necessity of poisoning the total acreage on the plantation may be
avoided.

After powdered arsenate of lead the best insecticide for the cotton
caterpillar is Paris green. As has been indicated, however, even
small amounts of this substance are likely to injure the foliage.
Such injury may not become apparent until several weeks after the
application. Nevertheless, the burning of the tender leaves will
show eventually in the stunted condition of the plants. This diffi-
culty may be overcome to some extent by the use of air-slaked lime
and Paris green in equal parts. Whether the lime is used or not,
flour should be used with the Paris green in equal parts. This will
assist greatly in causing the poison to adhere to the foliage.

London purple can also be used, but it is much less valuable than
Paris green on account of the frequent occurrence of free arsenic
which causes burning of the foliage.

White arsenic should not be used on cotton. It will kill the cater-
pillars, but will burn the foliage to such an extent that it does more
harm than good.

METHOD OF APPLYING THE POISON".

The method of application by means of sacks applied to a pole
carried on horseback through the fields, which came into general use
some years ago. will be found to be perfectly satisfactory. By this
means a single farm hand can poison 2 rows at a time and cover
about 20 acres during a day.

Tli.' apparatus for making the application is simple. A >trip of
hardwood 3 inches in width. 1 inch thick, and 1 font longer than the
distance between the rows should be selected. Two 1-inch holes
should be bored through the >tick 6 inches from either end. The
>aeks to contain the poison should made of 8-ounce duck or similar
material. Flour sacks will answer the purpose, but when powdered
arsenate of lead i> used, two thicknesses will he required on account"
of the extreme fineness of the poison. The >ack- should measure 6

THE COTTON WORM OB COTTON CATERPILLAR. '.'

by 20 inches and should be left open on one of the long sides. The
open margins are then tacked on the ends of the pole, forming a
which i- to be filled with the poison by mean- of a funnel inserted in
the auger hole.

Care should be taken to determine whether the right amoui.'
D is being applied. Tlu- can be easily don*- by weighing the
pole and sacks before and after a known area has been treated.
Unless this is done there is likely to be a waste resulting from the
application of too much poison, or it may be found that the amount
that is being applied is insufficient to cover the cotton. The operators
should be instructed to see that the poison falls evenly upon the
plants. If too much or too little is being applied the amount can be
easily regulated properly by varying the amount of jarring of the
pole. It i> important that the sacks do not come into contact with
the cotton 1> - If they do the poison will n<>t pass th:
readily and it will be found that the amount applied is too small.

CAUTION".

Arsenate "f lead and the other arsenicals t<> which reference has
been made are violent poisons, but there is no danger in their us
cotton if a few common-sense precautions are taken. The only
of poisoning of dome-tic animals known have been where stock was
allowed to break into the cotton fields soon after poisoning or where
some of the poison was carelessly thrown upon the grass. The only
precautions that are necessary are to keep live stock out of the
fields after poisoning and to avoid throwing any of the poison on
tation that will be devoured by live stock. It is advisable in
some i ses to muzzle the mules upon which the riders are mounted
when the application is being made.

There is practically no danger of poisoning live stock after one or

two heavy rains subsequent to the application of the poison, or, in

'10 rain fall-, after an interval of about three week- has elapsed.

The arsenical poisons __ ivatewounds - - >>n manor domestic
animal-. I - quently all places where the skin has been broken
should be covered by some mean-, or at any rate washed carefully
after the work has been done. In order to avoid the possibility of
injury to the mule-, it is advisable to throw several buckets of water
over them after the work i- done.

- • I MARY.

For the control of the cotton worm the use of powdered arsenate

of lead at the rate of 2 pounds per acre is advised above all other

mean-. This substance doe- not need to be mixed with any other

material. Pari- green, if used, should be mixed with lime and flour

bed.

UNIVERSITY OF FLORIDA

10 THE COTTON WORM OK COTTON

3 1262 09216 5801

The work of poisoning the insect should be undertaken as soon as
injury becomes apparent in any portions of the fields. By this means
the expense of control will be greatly reduced.

In regions where the boll weevil is abundant the planter should
take care not to poison the caterpillar too early. If he does so the
production will certainly be reduced. Where the weevil occurs in
considerable numbers no poisoning for the caterpillar should be done,
unless there is considerable ragging of the leaves before the earliest
bolls are three-fourths grown.

Approved:

James Wilson,

Secretary of Agriculture.
Washington, D. C, April 12, 1912.

ADDITIONAL COPIES of this publication
-fi- may be procured from the Superintend-
ent of Documents, Government Printing
Office, Washington , D. C. . at 5 cents per copy