PACKARD.] 



THE EUROPEAN CABBAGE-BUTTERFLY. 



749 



antemiio reaching to the end of the wings; the second pair of legs reaching half-way 

 between the end of the wings and end of abdomen; while the tips of the third pair 

 of feet reach half-way between the second j)air of feet and the end of the abdomen. 

 It is from a line to a line and a third in length. 



lu the middle of September Mr. F. W. Putnam handed me one hundred 

 and tun cbrysalids, all but two of whi(;h were infested by these parasites 

 in both the larval and ])ui)al states; while from other chrysalids the adult 

 chalcid flies were emerging'. They continued to emerge until late in the 

 autumn. The infested chrysalids of the butterfly could be easily distin- 

 guished by the livid and ctberwise discolored and diseased appearance 

 of tbe body, wbile those unattacked had preserved the fresh color, and 

 the tail moved about readily ; the diseased ones becoming stiff and more 

 or less dried. 3([r. Putuam thinks that at least two-thirds of the chrys- 

 alids of tbis butterfly, hundreds of which had in the early autumn sus- 

 pended theoiselves about his house and fences, bad been attacked by 

 these useful allies. 



Oil opening tbe body of the infested chrysalids I found about thirty 

 parasites in different stages of growth, in one case thirty two, in an- 

 otber only twelve. We can readily see how efiicieut these minute in- 

 sects become in reducing tbe numbers of their hosts. A large propor- 

 tion of the Ptcromalus undoubtedly winter over in the body of the 

 chrysalis, the adult insects appearing in the spring. In England Mr. 

 Curtis found the fly in June, so that evidently there is an autumn and 

 spring brood of flies. 



Another parasite is the larva of a parasitic fly, Tachina (Fig. 17, 

 enlarged tliree times), the adult form of which closely resem- 

 bles tbe common house fly. It is a flattened, cylindrical mag- 

 got, both ends of tbe body rounded much alike. The mouth 

 parts are partly aborted, tbere being only two retractile 

 boruy mandibles by which the fatty portions of its host is 

 eaten. 



Bt'sides this large Tachina I found a minute fly in the same 

 bottle with a number of the cbrysalids of the butterfly, and am 

 inclined to think that it may have lived parasitically in them, 

 but would not be contident that it is so. It is a small black 

 fly, about a line in length, and with dark wings. 



The male butterfly (Fig. 18) is white, with the tips of the fore wings 



Fig. ly. — Enropean Cabbage Butterfly, male. 



black, dusted with white, while on the fore wings is a single, and in the 

 female tbere are two large black spots, situated two-thirds of the 

 distance from the base to the outer edge of the wing. It expands 

 about two inches. The female lays her eggs singly on the under side of 

 tbe leaves. The caterpillar (Fig. 20, a) is green, and so densely clothed 

 with minute hairs as to be velvety; it has a yellowish stripe down the 

 back and anotber along each side, tbe belly being of a paler, brighter 

 green ; it is often more than an inch long, and about as thick as a large 



