. Annual report. 1st-12th, 1867-1878. Geology. PACKARD.] THE EUROPEAN CABBAGE-BUTTERFLY. 749 antenniG reaching to the end of the wings; the second pair of legs reaching half-^^ay hetween the end of the wings and end of abdomen; while the tips of the third pair of feet reach half-way between the second pair of feet and the end of the abdomen. It is from a line to a line and a third in length. In the middle of September Mr. F. W. Putnam handed me one hundred and ten chrysalids, all but two of which were infested by these parasites in both the larval and pupal states; while from other chrysalids
. Annual report. 1st-12th, 1867-1878. Geology. PACKARD.] THE EUROPEAN CABBAGE-BUTTERFLY. 749 antenniG reaching to the end of the wings; the second pair of legs reaching half-^^ay hetween the end of the wings and end of abdomen; while the tips of the third pair of feet reach half-way between the second pair of feet and the end of the abdomen. It is from a line to a line and a third in length. In the middle of September Mr. F. W. Putnam handed me one hundred and ten chrysalids, all but two of which were infested by these parasites in both the larval and pupal 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 otherwise discolored and diseased appearance of the body, while those unattacked had preservedlhe fresh color, and the tail moved about readily ; the diseased ones becoming stiff and more or less dried. Mr. Putnam thinks that at least two-thirds of the chrys- alids of this butterfly, hundreds of which had in the early autumn sus- pended themselves about his house and fences, had been attacked by these useful allies. On opening the body of the infested chrysalids I found about thirty parasites in different stages of growth, in one case thirty two, in an- other only twelve. We can readily see how efficient these minute in- sects become in reducing the numbers of their hosts. A large propor- tion of the Pteromalus 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 enlarged three times), the adult form of which closely resem- bles the common house fly. It is a flattened, cylindrical mag- got, both ends of the body rounded much alike. The mouth parts are partly aborted, there being only two retrac
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