The caterpillars feed upon the leaves of various species of oak, birch, willow, and linden. The eggs are laid upon the extreme tip of the leaves, and the infant caterpillar, feeding upon the leaf in immediate proximity to the point where it has been hatched, attaches bits of bitten leaf by strands of silk to the midrib, thus stiffening its perch and preventing its curling as the rib dries. Out of bits of leaves thus detached it constructs a packet of material, which it moves forward along the midrib until it has completed its second moult. By this time winter begins to come on, and it cuts away for itself the material of the leaf on either side of the rib, from the tip toward the base, glues the rib of the leaf to the stem by means of silk, draws together the edges of the remaining portions of the leaf, and constructs a tube-like hibernaculum, or winter quarters, exactly fitting the body, in which it passes the winter.
[a]Fig. 107.]—Leaf cut away at end by caterpillar of Basilarchia (Riley).
[a]Fig. 108.]—Hibernaculum, or winter quarters, of larva of Basilarchia.
There are a number of species of the genus found in the United States, the habits of which have been carefully studied, and they are among our most interesting butterflies, several species being mimics of protected species.
(1) Basilarchia astyanax, Fabricius, Plate XXII, Fig. 1, ♂; Plate III, Figs. 17, 21, 25, larva; Plate IV, Figs. 12, 13, chrysalis (The Red-spotted Purple).
Butterfly.—This common but most beautiful species is sufficiently characterized by the plate so far as the upper surface is concerned. On the under side the wings are brownish, banded with black on the margins; the lunules are on this side as above, but the inner band of spots is red. There are two red spots at the base of the fore wings, and four at the base of the hind wings. The palpi are white below, and the abdomen is marked with a lateral white line on each side. Expanse, 3.00-3.25 inches.
Egg.—The egg, which resembles somewhat closely that of B. disippus (see p. 3, Fig. 1), is yellowish-green, gradually turning dark brown as the time for the emergence of the caterpillar approaches.
Caterpillar.—The caterpillar is so well delineated in Plate III, Fig. 17, as to obviate the necessity for a lengthy verbal description.