Genus Basilarchia Scudder (the White Admirals)
Rather large butterflies. Fore wings subtriangular, rounded at the apex, and lightly excavated on the lower two thirds of the outer margin. Hind wings rounded, somewhat crenulate. Egg nearly spherical (see Plate C, Fig. f) pitted with large hexagonal cells. The caterpillar in its mature state cylindrical, with the second segment adorned with two prominent club-shaped tubercles, and the fifth, ninth, and tenth segments also having raised tubercles (see Plate C, Fig. h). They feed upon oaks, birches, willows, and lindens, preferably the two latter. The caterpillars after hatching hibernate in little winter quarters, which they make out of the fragment of a small leaf, which they tie together with silken threads, and also secure to the twig by a few strands. The chrysalis has a projecting boss on the back; the head is either rounded or slightly bifid.
There are a number of species in the United States, several of which mimic other butterflies in a singular manner, B. disippus closely resembling Anosia plexippus. The caterpillars do not pupate until summer has come; the butterflies take wing when the lindens bloom.
(1) Basilarchia astyanax (Fabricius), Plate XLIV, ♀ (The Red-spotted Purple).
Our figure gives a good idea of the upper side of the wings. On the lower side the wings are brown, banded with black on the margins, the inner row of marginal spots being red, with two red spots at the base of the fore wings, and four such spots at the base of the hind wings. Palpi white below; a white stripe along the sides of the abdomen. Expanse 3.00-3.25 inches. The egg and caterpillar are shown on Plate C. The caterpillar is found on a variety of plants, but most commonly on lindens, willows, and wild cherry trees.
Found all over the United States and Canada, as far west as the Rocky Mountains, but not in the very hot lowlands of the Gulf region. Is said to occur on the uplands of Mexico.
Between B. astyanax and the following species, B. arthemis, there is more or less affinity. They represent two lines of evolution from a common ancestry, and there are evidences of atavic reversion to type constantly occurring in both forms. They even occasionally interbreed with each other, and hybrids are not altogether uncommon. The whole genus in fact is in a more or less plastic state, and well deserves the careful attention of biologists.
(2) Basilarchia arthemis (Drury), Plate XLV, ♂ (The Banded Purple).
Our figure shows the upper side of the form which is most usual. It will be seen that there are red spots on the hind wings behind the white band. There is a variety called proserpina in which the white band becomes very narrow and the red spots almost or entirely disappear. When the white band and the red spots wholly disappear, as they sometimes do, it is almost impossible to distinguish this species from B. astyanax. Expanse 2.50-2.75 inches. The egg has “kite-shaped” cells. The caterpillar feeds on willows, hawthorns, and wild apple and plum trees.
Found in Canada, New England, and southward in Pennsylvania upon the higher ranges of the mountains. It is a northern form. It has not thus far been recorded from the western half of the continent, where it is replaced by a somewhat similarly marked, but larger, species, known as B. Weidemeyeri. The latter insect is found as far east as western Nebraska and Colorado. I have taken it very frequently in Wyoming about Laramie Peak, where it seems to be a common insect in the wooded canyons.
(3) Basilarchia disippus (Godart), Plate XLVI, ♂; Plate C, Fig. f, egg; Fig. h, larva. (The Viceroy).
Mimics Anosia plexippus. Range from Canada to the Gulf.
This is one of the most striking cases of mimicry which occurs in our fauna.
(4) Basilarchia lorquini (Boisduval), Plate XLVII, ♂ (Lorquin’s Admiral).
Easily distinguished by white bar at end of cell of fore wing and red spot at apex. Expanse 2.25-2.75 inches.