'
Circular No. 9)
I UHJH
I oited States Department of Agricu
BUREAU OP ENTOMOLOGY,
L. O. HOWAK1) KntomologUt »nd Chief..! Bw
THE BAGWORH.
(TTtyridopUryx tphemei 11. iu
By l 0. I fott uuj and I II Cbittkndi
m i: \\ \rri\i;\Mi \m- NATUB1 "i kTTACK.
Shade tret-, -hrui>-. and hedges, and in particular evergreens, are
much Bubject to injury by a medium sized caterpillar which ha- a
curious habit <>t' crawling about <>n the infested trees in a bag-like case,
whence its common name of bagwormor basket worm.
In the shelter <>(' these cases the insects undergo all
their transformations, after which the bags remain
attached to the plant- for some time and are conspic-
uous objects on leafless trees and shrubs in late autumn
mill in winter. Like the tussock moth and the tall
webworm* tin- species i- preeminently a pest on the
Btreets and in park- and private grounds <>!' cities and
towns and is even more subject to fluctuation in num-
bers. It i-. however, more limited in distribution
and nut found a- a rule north of southern New York
and the central portions of Pennsylvania and Ohio.
South of these points it i- in certain years very trou-
blesome and tin- subject of much complaint Such a
year was 1907, when the bagworm attracted greater
attention than any other tree defoliator. Numerous
complaints were received of injuries in the region
mentioned, and especially from the State- of New
Jersey, Pennsylvania, Maryland. Virginia, West Virginia, Ohio,
Indiana, and Illinoi-. d"he natural enemies of thi- insect (see p. »'•>
were comparatively scarce, and there i- a strong possibility of a recur-
rence of injuries in the year- to come.
The general appearance of the bagworm i- shown in figure I. which
illustrates the caterpillar when nearly full grown, in it- characteristic
bag. When removed from it- bag it look- a- shown in figure 8, • '.
which represents the larva H maturity. A4~tlu- period in it- develop-
I •. I — Rac« ..mi
( Thyriilnplrryl
Natural -
tor i:
lerocnmp 18. A A.
- -Cir. 97—08 1
ment it may attain a length of about three-fourths of an inch. The
body is soft in texture and dull brownish or blackish, while the head
and thoracic Begments arc horny and whitish, mottled with dark
brown.
ORIGINAL HOME AM) PRESENT DISTRIBUTION.
The bagworm is unquestionably native to North America. It
abounds in the Southern States, and its proper home— that is to say,
the part of the country where it reaches its maximum — is in the Lower
Austral life zone. It extends thl'OU'gh a considerable portion of the
Upper Austral zone, hut there are indications that it has gradual!}'
spread into this territory from more southern regions." The shade
trees of Baltimore. Washington, St. Louis, and other more southern
cities are frequently defoliated by this insect. Northward it occurs
Kn.. -. — Bagworm ( Thyridopteryxephemerstformia} : a, Fall-grown larva: /<. head of same: c, male pupa;
• /, female pupa; e, adult female; /, adult male. All enlarged (from Howard .
through New Jersey and at many points in Pennsylvania, including
the cities of Harrisburg, Elliottsburg, Allentown, and Swarthmore.
Farther west it has been found at Columbus, Marietta, South Salem,
and other localities in Ohio, at several points in West Virginia, at
Brooklyn, Ind.,in Pecatonica, ThompsonviUe, and Allendale. 111., and
so on west to Oklahoma. Everywhere south of these localities, except
in the immediate Gulf region, it abounds. In the East it is commonly
found in New York City and Brooklyn, and at several points on Long
Island. In the Hudson River Valley region it has been recorded by
Felt at Yonkers and Mount Vernon, and has been collected at New
" In the main the bagworm is one of those characteristic forms like the wheel-bug
[Arilus cristatus Jj.) , the Carolina mantis [Stagmomantis Carolina L.), and the la'
g stage within the old female
bags, and for this reason hand-picking in winter time is an efficacious
remedy. In the late spring the young hatch from the eggs, crawl out
upon the twigs, make their way to the nearest leaf, and immediately
begin to feed and to construct cases or bags for themselves. They
spin a large amount of silk and attach to it, for additional strength
and protection, bits of leaf or of twig, evidently attempting to disguise
the nature of the case as well as to strengthen it. The larva i-
remarkably soft-bodied, except for its head and strong thoracic plates,
and it is necessary that the soft abdomen should have some protection.
The construction of the bag of an allied species was carefully studied
by H. G. Hubbard, and it is a very interesting performance.
The young larva (tig. 4, ut it- head
and slow ly walk- off.
A- tin- caterpillar grows
tin' case i- constantly
enlarged, bits of twigs
and any ot her small
objects being used to
ornament the outside,
and these objects will
vary w itli the kind of
tree 14)011 w li i c li the
caterpillar i- feed i n g.
While the Ian a is small
it carries it- case erect,
t>ut \\ hen it i- larger the
case hangs dow n ( fig. 1 1.
The larval skin is cast
four times, and during
the molting the mouth of
the bag is kept closed
w ith silk. There is a
small opening in the
extremity of the hat:
through which excre-
ment and cast skins are pushed. The male bags are smaller than those
of the female-, reaching a length of about an inch, while those of the
females are much larger. Toward the end of August, about Wash-
ington, I>. ('.. the larva complete- it- growth, attache- it- bag firmly
by a silken band to a twig, strengthens it inside with an additional
layer >>i -ilk. and within this retreat, which now becomes its COOOOn,
transforms to pupa with its head downward. The pupal period lasts
about three week-, and then the imago emerges. The male chrysalis
work- it- way out of the lower opening, and the winged moth issues
-Cir. '.<7-(is 2
Pic 1 a Newly hatched bagworui before makli
ast beginnii • nearly com-
plel larva
hi 1 it lir-t molt Highly 1
through the cracking skin, leaving the chrysalis hanging from the bag,
as shown at c, figure ">. The chrysalis of the female docs not push its
way at all out of the bag, but the skin cracks and the female gradually
works her way partly out, her head reaching the lower end of the bag,
(lig. 5, d). The males fly about, seeking the hags of the females, and
when one is found in which the head of the female is near the end.
showing that she has emerged from her chrysalis >kin. the male pushes
his enormously protrusive and, in fact, telescopic genital apparatus up
into the bag to the anal end of the female and fertilizes her. The
female then works her way back into the chrysalis skin, gradually filling
it with eggs until more than half of it is filled, scattering in among the
eggs some of the sparse hairs from her body. Having done this she
forces her shriveled
body out of the open-
ing, falls to the ground,
and dies. The eggs re-
main in this way until
the following spring,
when they hatch, as
previously described.
There is thus only one
generation annually.
Note. — There is a possi-
bility that the bags of this
extremely common insert
might be made commer-
cially useful. Itssilk, from
a practical standpoint, has
always been ignored, but it
is firmer and stronger and
more easily spun as carded
silk than that of must other
native silk cocoons.
Fig. 6.— Bagworm at (a, h. c) successive stages of growth,
bag; •/. female bag. Natural size i from Howard I.
Male
NATURAL ENEMIES.
Although apparently well protected from the attacks of birds b}'
its tough case, the bagworm is somewhat extensively parasitized by
several forms of ichneumon and chalcis Hies, most of them species
which affect also similar tree-feeding caterpillars. Prominent among
these is the common Pimpla inquisitor Say (fig. 6), which, however.
more commonly parasitizes the tussock moth and tent caterpillars.
The related P. conquisitor Say is also a parasite of the bagworm and
a third species of ichneumon, Allocota ( II< mitt les) thyridopU rigis Riley
(tig. 7), is usually the most abundant of all. Four or live individuals
of this species comnionlj' infest a single bagworm, spinning for them-
selves white silken cocoons within the bag.
fCir. 97
" Malacosoma spp.
The species last mentioned was for manj years credited with being
a primary parasite of the bagworm, although recenl observations
would indicate that it is a secondary parasite when infesting other
Kr. • male, from
Pro, l.—AUc M ii henlaiged
caterpillars. This mighl be explained by the hypothesis that this
parasite oviposits onlj in cocoons or cases of firm texture, and there
fore can not be the primary parasite of an insect w bicb is not provided
with a case of t liat character.
<^K
Certain chalcis flies also breed in
the bags of tin- insect. These include
Sjnlochalcls maria Riley Mi;.'. B),
Chalets ovata Saj (fig. 9), and the
common little Dibrachya boucheanus
Rate. (fig. 10). Tin- last i- a hyperparasite, in the case of the i>avr-
worm probably secondary, ami in the case <>t' other cater]
rpillar
• 8
tertiary parasite. Habrocytits thyridopterigi* Ashm. (fig. 11) is
assumed to be a tertiary parasite on Allocdta thyridopterigis Riley,
when the latter is a secondary parasite of the tussock moth, but may
be secondary when breeding in the cases of the bagworm.
REMEDIES.
Fig. 10. — Dibrachys boucheanus: Adult female and antenna of male.
Much enlarged (from Howard).
When the bagworm occurs upon deciduous trees it can be controlled
by hand-picking the bags in the winter, but when it affects evergreen
trees it is practi-
cally impossible to
apply this remedy
with profit unless
the plants arc badly
defoliated. There-
fore for the treat-
ment of evergreens
spraying is a neces-
sity.
The methods of
controlling shade-
tree pests in cities
and towns, as out-
lined in Farmers'
Bulletin No. 99, a on pages 25-29, are in part applicable to this species.
This bulletin should be read by persons who have experienced trouble
from the depredations of the bagworm.
Collecting the bags. — -?•
One of the most important
remedies consists in gath-
ering the bags with the
contained insect by hand
and either burning them
or preserving them to lib-
erate the useful parasites
which have been previ-
ously mentioned. This
work may be facilitated
by the use of a 12-foot
pole pruner or similar
appliance, and can be intrusted to those ordinarily unemployed, such
a- children and aged persons. Where the trees are very tajl it will
be necessary to use a long ladder. For best results the cooperation of
neighbors who are troubled with the same pest should be secured.
« This publication nuty be had gratis on application to the Department of Agriculture.
[Cir. 97]
Fig. 11.
-Habrocytus thyridopterigis.
How ard i.
Greatly enlarged (from
9
Ycr\ considerable immunitj from future injury will result bj care In
the employment of this method. It is particularly useful where on Ij
a few trees arc infested. The bags are Mich conspicuous objects on
defoliated or bare trees in w inter thai it i- not at all difficult to detect
them, l>ni in cases where comparatively fe^ insects are presenl on
evergreen trees 1 1 •« ■ \ are not so easily seen.
Encouraging ttu parasite*. When many trees are infested it is
advisable i<> keep the hand picked bags for a considerable time in
receptacles, such as barrels covered with netting, preferably of wire,
bo that the numerous beneficial parasites of tin- pest will be able to
issue in the spring and assist In the control of the bagworm the fol
lowing rear. One or two holes bored in the bottom of the barrel or
i»o\ will prevent water from accumulating and drowning the insects.
Where the bags can be placed in piles in an open -pace or inclosure
distant from trees and free from disturbance, the young insects, having
very limited powers of locomotion, will soon perish of starvation, as
they will not be able t<> reach the trees or shrubs after they batch.
Spratffng with arsenicals. ( )m evergreen, where the bags are more
or less difficult to find, band-picking can not be advised. A striking
instance < > t" the futility of this method under such circumstances was
given by Prof. ('. V. Rilej in hi- testimony at a conference <>n the
gipsy moth in 1891. He said that he once trie. I to protect a cedar tree
not more than »; feet high, upon his own grounds at Washington, i>\
hand-picking. lie worked tin- two consecutive months picking "H
small bags from that tree, the progeny of not more than two female-.
Almost daily he went to the tree and found fresh specimens which he
had overlooked the day before. For evergreen tree-, therefore, an
arsenical spray is the best remedy, [n connection with the Btory of
hi- experience just related, Professor Riley stated that he had abso
lutely -topped injury by the bagworm on large tree- in the Smith
SOnian grounds by -pray inc. and in the summer of L895 we had a
similar experience on the grounds of the Agricultural Department at
Washington. Tree- sprayed with Paris green at the rate of l pound
to 150 gallons of water were completely rid of larva? of the bagworms.
It i- easier to reach the bagworms on evergreen than on large-leaved
deciduous -hade tree-, -uch a- maple and elm. but if carefully carried
out spraying will result in the destruction of the bagworms, so that
the collection of the bags in winter will riot he necessary. Arsenate
of lead at the rate ^i l pound of the prepared paste f"iin t.> from !'•'>
to 50 gallons of water will lie found even more useful than the Paris
green, as it- greater adhesiveness renders it less likely to he washed
off by rains, which in some seasons frequently occur almost daily at
the time when the larv;e are beginning to work.
fCir. 97]
10
The best time to apply the arsenical is when the egg* hatch, or
shortly afterwards, and the best methods of spraying shade trees are
disclosed in Farmers' Bulletin No. !'!».
Approved:
James Wilson,
Secrt tary of . Igricultun .
Washington, D. ('.. December®, 1UQ7.
[Cir. 97]
O
UNIVERSITY OF FLORIDA
3 1262 09216 5306