MILKWEED BUTTERFLY. A cosmopol itan butterfly (.t nosiu plesippus) which is found in nearly all parts of the world where milkweeds (Aselepias) grow. It is a large reddish species, with its wing-veins blackened, and its larva is striking in color, being grayish-white and yellow ish, transversely banded with black, giving it a zebra-like appearance. The chrysalis is delicate pale green with bright golden spots, and hangs from the leaves or stems of the food plant. The milkweed butterfly is a famous species for sev eral reasons. It is one of the strongest flyers known among the Lepidoptera ; specimens have been taken on vessels many hundreds of miles from the land, and there is in the United States an annual migration northward in the spring from the States bordering on the (hill of Mex ico. (See MIGRATION OF ANIMALS.) These flights, aided by the south winds, may reach up into Canada, the butterflies occasionally alighting and laying their eggs upon the milkweeds. In the autumn there is a return migration south, and the butterflies hibernate only in the Southern States, hidden away beneath the hark of trees and in other protected places.
Ordinarily the butterflies frequent open ground, but when they congregate, as at night and in cloudy weather, they are found resting on the stems of herbaceous plants, usually in the open spaces of forests, and in enormous numbers.
They will alight upon the lee side of a tree, and particularly on the lower hranches, in such vast numbers as almost to hide the foliage and to give their color to the trees. If disturbed, they rise like a flock of birds, hut immediately settle again. Sometimes a tree will be so festooned with butterflies that it appears, at a. short dis tance, to be covered with dead leaves.
This butterfly is one of the especially protected species, and is provided with scent-scales, 'an droconia,' which are supposed to make the insect distasteful to its natural enemies. It is the commonest and most widespread representative of the large group of butterflies which are thus protected, and is mimicked in coloration by other non-protected species, e.g. in the United States by Basilarehia disippus. Consult Scudder, The. Life of the Butterfly (New York, 1893). See the articles MimicRY; VICEROY; and BUTTER FLIES AND MOTHS.