It may be added that the geographical range of the butterfly extends eastwards through Asia as far as Japan. A form, known as the Alaskan Swallow-tail, is found in Alaska.
The following ten species belong to the Pierinæ, another sub-family of Papilionidæ.
The Black-veined White (Aporia cratægi).
The Black-veined White (Plate [4]) may be at once recognized by its roundish white wings and their conspicuous veins, which latter are black in the male butterfly, and in the female brownish on the main ones (nervures) and black on the branches (nervules). As the scales on the wings are denser in the male than in the female, the former always appears to be the whiter insect. On the outer margin of the fore wings there are more or less triangular patches of dusky scales, and these in occasional specimens are so large that their edges almost or quite meet, and so form an irregular, dusky border to the fore wings. These patches are also present on the hind wings, but are not so well defined. Sometimes the patches are absent from all the wings. The fringes of the wings are so short that they appear to be wanting altogether. The early stages are figured on Plate [3.]
The egg is upright and ribbed from about the middle to the curiously ornamented top, which appears to be furnished with a sort of coronet. The colour is at first honey-yellow, then darker yellow, and just before the caterpillar hatches, greyish. The eggs are laid in a cluster on the upper side of a leaf of sloe, hawthorn, or plum, etc., in the month of July.
The caterpillar when full grown is tawny brown with paler hairs arising from white warts; the stripes along the sides and back are black. The under parts are greyish. The head, legs, and spiracles are blackish. Caterpillars hatch from the egg in August, and then live together in a common habitation which is formed of silk and whitish in colour. They come out in the morning and again in the evening to feed, but a few leaves are generally enclosed in their tenement. In October they seem to retire for the winter and reappear in the spring. During May they become full grown and then enter the chrysalis state. The butterflies are on the wing at the end of June and in July.
Larger Image