yal ar SB 818 10. 97 Issued February 6, 1908. ig aited States Department of Agriculture, BUREAU OF ENTOMOLOGY, L. O. HOWARD, Entomologist and Chief of Bureau. THE BAGWORM. ( iieaiosioni ephemerxformis Haw. ). By L. O. Howarp and F. H. CxHirrenpen. GENERAL APPEARANCE AND NATURE OF ATTACK. Shade trees, shrubs, and hedges, and in particular evergreens, are much subject to injury by a medium-sized caterpillar which has a curious habit of crawling about on the infested trees in a bag-like case, whence its common name of bagworm or basket worm. In the shelter of these cases the insects undergo all their transformations, after which the bags remain attached to the plants for some time and are conspic- uous objects on leafless trees and shrubs in late autumn and in winter. Like the tussock moth” and the fall webworm?” this species 1s preeminently a pest on the streets and in parks and private grounds of cities and towns and is even more subject to fluctuation in num- bers. It is, however, more limited in distribution and not found asa rule north of southern New York and the central portions of Pennsylvania and Ohio. South of these points it is in certain years very trou- blesome and the subject of much complaint. Such a year was 1907, when the bagworm attracted greater et cae ally ves attention than any other tree defoliator. Numerous — ¢pnemerzformis). complaints were received of injuries in the region dabemc? (af- mentioned, and especially from the States of New Jersey, Pennsylvania, Maryland, Virginia, West Virginia, Ohio, Indiana, and Illinois. The natural enemies of this insect (see p. 6) were comparatively scarce, and there is a strong possibility of a recur- rence of injuries in the years to come. The general appearance of the bagworm is shown in figure 1, which illustrates the caterpillar when nearly full grown, in its ioe: bag. When removed from its bag it looks as hae in figure 2, a, which represents the larva et maturity. At this period in its oo « Hemerocampa leucostigma 8. & A. b eae cunea a 20833—Cir. 97 2 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 segments are horny and whitish, mottled with dark brown. ORIGINAL HOME AND 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 through a considerable portion of the Upper Austral zone, but there are indications that it has gradually 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 oir aa Nee gostei A thin iy Fic. 2.—Bagworm ( Thyridopteryx ephemerxformis): a, Full-grown larva: b, head of same; c, male pupa; d, 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, Thompsonville, and Allendale, Ill., 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 L.), the Carolina mantis (Stagmomantis carolina L.), and the larger digger wasp (Sphecius speciosus Dru.), true southern forms which are gradually extending their northward range by following the seacoast or valleys, or, if carried ace.dentally northward upon railroad trains, establishing themselves at points beyond their former habitat. [Cir. 97] (Original.) Fic. 3.—Arborvite infested by bagworms. (Cir. 97] 4 Haven, Conn., but it is not known to be injurious in these localities. It has been sent to the Bureau of Entomology from Springfield, Mass., but probably does not breed there. FOOD PLANTS. The bagworm, although a very general feeder, displays a particular fondness for evergreens of all kinds and especially for arborvite, hence it seems probable that one or the other of these was its original or normal food plant (fig. 3). The species becomes exceedingly abun- dant every few years, and at such times it may be found on shade, orchard, and forest trees of nearly all kinds. Itis fond of the maples, particularly the cut-leaved and silver maples, and the related box elder; also of the poplars and mulberry, less so of the elms, and apparently still less so of the oaks. It feeds more or less freely, how- ever, on most other trees and shrubs, and even on many low-growing semi-woody plants, such as elder, mallows (Hibiscus), and ragweed (Ambrosia trifida). Thus, in the absence of its choice food plants, it is able to subsist on the foliage of almost any of the plants of the character enumerated and which may be available, but it does not seem to live on grasses and herbaceous plants generally. HABITS AND LIFE HISTORY. The bagworm overwinters in the egg 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 is 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 (fig. 4, ~) cuts off with its jaws a small fragment of leaf which it places between its front legs, gradually forming a pile fastened loosely with silk. When the pile becomes a transverse tangle about as long as the body it is fastened at each end loosely to the surface upon which it rests; then the caterpillar, after placing itself at right angles, dives under the mass, turning a complete somersault, so that it lies on its back, bound down by the fillet. It then twists around and stands upon its feet, having its neck under a sort of yoke (fig. 4, 0). It makes the yoke into a complete collar, adding bits to each end until [Cir. 97] , 5 the circle is complete. Then row after row of fragments is added until the case becomes a hollow cylinder (fig. 4, ¢). One end is then closed up and the inside lined with a tough coating of silk, the case being then extended upright and fastenedat one end. When it is fully completed the larva crawls away, with the case carried upright like a cap on the upturned end of its body. In the illustration d shows a completed bag made by the young larva, tightly appressed to the flat surface, the larva being concealed within. Such bags may frequently be found on leaves, and are quite puzzling to the uninitiated until the larva pokes out its head and slowly walks off. As the caterpillar grows the case is constantly enlarged, bits of twigs and any other small objects being used to ornament the outside, and these objects will vary with the kind of tree upon which the caterpillar is feeding. While the larva is small it carries its case erect, but when it is larger the case hangs down (fig. 1). The larval skin is cast four times, and during the molting the mouth of the bag is kept closed with silk. There is a Fic. 4.—a, Newly hatched bagworm before making its case; small opening in the b, same just beginning case; c, showing case nearly com- : 2 pleted; d, completed case, insect concealed within; e, larva extremity at the bag after first molt. Highly miaenided (original). through which excre- ment and cast skins are pushed. The male bags are smaller than those of the females, reaching a length of about an inch, while those of the females are much larger. Toward the end of August, about Wash- ington, D. C., the larva completes its growth, attaches its bag firmly by a silken band to a twig, strengthens it inside with an additional layer of silk, and within this retreat, which now becomes its cocoon, transforms to pupa with its head downward. The pupal period lasts about three weeks, and then the imago emerges. The male chrysalis works its way out of the lower opening, and the winged moth issues 20833—Cir. 97—08——2 . 6 through the cracking skin, leaving the chrysalis hanging from the bag, as shown atc, figure 5. Thechrysalis of the female does not push its vay 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, (fig. 5, d@). The males fly about, seeking the bags 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 skin, 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. Nore.—There is a possi- bility that the bags of this extremely common insect 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 Fic. 5.—Bagworm at (a, b, c) successive stages ot. growth. c, Male gilk than that of most other bag; d, female bag. Natural size (from Howard). native silk cocoons. NATURAL ENEMIES. Although apparently well protected from the attacks of birds by its tough case, the bagworm is somewhat extensively parasitized by several forms of ichneumon and chalcis flies, most of them species which affect also similar tree-feeding caterpillars. Prominent among these is the common /%mpla 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, A//ocota ( Hemiteles) thyridopterigis Riley (fig. 7), is usually the most abundant of all. Four or five individuals of this species commonly infest a single bagworm, spinning for them- selves white silken cocoons within the bag. «@ Malacosoma spp. [Cir. 97] 7 The species last mentioned was for many years credited with being a primary parasite of the bagworm, although recent observations would indicate that it is a secondary parasite when infesting other Fic. 6.—Pimpla inquisitor: Female, from side. Enlarged (from Howard). Fic. 7.—Allocota (Hemiteles) thyridopterigis. Muchenlarged (original). caterpillars. This might be explained by the hypothesis that this parasite oviposits only in cocoons or cases of firm texture, and there- fore can not be the primary parasite of an insect which is not provided with a case of that character. Much enlarged (after Fic. 8.—Spilochaleis mariz. Riley). Certain chalcis flies also breed in the bags of this insect. These include Spilochalcis marie Riley (fig. 8), Chalcis ovata Say (fig. 9), and the — Fic. 9.—Chalcis ovata: Adult. Enlarged common little Dibrachys boucheanus sack mango Ratz. (fig. 10). This last is a hyperparasite, in the case of the bag- worm probably secondary, and in the case of other caterpillars ¢ [Cir. 97] 4 8 tertiary parasite. Habrocytus thyridopterigis Ashm. (fig. 11) is assumed to be a tertiary parasite on