Butterfly.—Generally large, and often with the hind wings adorned by tail-like projections. The most characteristic structural feature of the group is the absence of the internal vein of the hind wings. The submedian vein occupies the position usually held in other subfamilies by the internal.
Early Stages.—In that portion of the group which includes the genus Parnassius and its allies, the caterpillars are not, so far as is known, provided with scent-organs, and pupation takes place upon the ground, or among loosely scattered leaves, which are interwoven, at the time of pupation, with a few strands of silk. The genus Papilio and its allies have large, fleshy, more or less cylindrical caterpillars, possessed of osmateria, or offensive scent-organs, and a general resemblance runs through the chrysalids of all species, which are attached by a button of silk at the anal extremity and supported in the middle by a silk girdle.
Genus PARNASSIUS, Latreille
(The Parnassians)
"Some to the sun their insect wings unfold, Waft on the breeze, or sink in clouds of gold; Transparent forms, too fine for mortal sight, Their fluid bodies half dissolv'd in light."
Pope.
Butterfly.—Of medium size, with more or less diaphanous wings, generally white or yellow in color, marked with black spots and round pink or yellow spots, margined with black. The head is relatively small, thickly clothed with hairs. The antennæ are short and straight, having a gradually thickened club. The palpi are very thin, straight, and clothed with long hairs. The wings are generally translucent on the margin, with a rounded apex. The upper radial is lacking. The subcostal is five-branched, the third, fourth, and fifth nervules being emitted from a common stalk which springs from the upper outer angle of the cell. The first subcostal nervule rises well before the end of the cell; the second from the same point from which the stalk which bears the other three nervules springs. The cell of the hind wing is evenly rounded at its outer extremity. The inner margin of the hind wing is more or less excavated.
Early Stages.—The egg is turban-shaped, flattened, profusely covered with small elevations, giving it a shagreened appearance. The caterpillars have very small heads. They are flattened, having a somewhat leech-like appearance; they are black or dark brown in color, marked with numerous light spots. The chrysalis is short, rounded at the head, and pupation takes place on the surface of the ground, among leaves and litter, a few loose threads of silk being spun about the spot in which transformation occurs.
The butterflies of this genus are classified with the Papilioninæ, because of the fact that the internal vein of the hind wings is always wanting, a characteristic of all papilionine genera.
[a]Fig. 149.]—Neuration of the genus Parnassius.