THE PAPILIONINAE
This is the subfamily of the true swallowtails, the largest and most distinctive of American butterflies. The hind wings are prolonged into two tail-like projections, and are characterized, by the absence of the internal vein. The caterpillars are all provided with peculiar V-shaped scent-organs called osmateria; these organs are thrust out just back of the head when the insect is disturbed, and give off an offensive odor, supposed to discomfit birds and other enemies.
Papilio troilus, the Green-clouded Swallowtail, is velvety black with a row of yellow spots along the margin of the fore wings. The marginal spots on the hind wing are pale green, and the whole outer half of the hind wing is clouded with the same greenish tinge. The female deposits her eggs on sassafras and spicebush leaves; the caterpillar is lead-colored or greenish, with a swollen thorax bearing two large eye-spots, and lives in a nest made of a folded leaf. Papilio troilus is common throughout the Atlantic States and in the Mississippi Valley.
Papilio turnus, the Tiger Swallowtail, is the magnificent yellow-and-black species found in practically every part of the United States. In the northern portion of its range the male and female appear very much alike, but in the South there are two distinct types of females. One female is black-and-yellow like its northern sisters; the other is black-and-blue, with no yellow at all except a few small crescents in the outer border of the hind wing. The black female, was for a long while considered a distinct species and called Papilio glaucus. Later, however, it was discovered that some of the eggs laid by the yellow turnus produced the black glaucus females, and that, conversely, the eggs of glaucus often produced the ordinary yellow-and-black Tiger Swallowtail. The smooth bluish-green eggs are usually found on the wild cherry leaves; the caterpillar is green, with enlarged thoracic segments bearing two large eye-spots like those of Papilio troilus.
Papilio ajax, the Zebra Swallowtail, is another striking member of this magnificent subfamily. The combination of green and black stripes, the blue and red crescents and the long tails on the hind wings, distinguish ajax immediately from any of its splendid fellows. There are at least three slightly different seasonal varieties of this butterfly, due probably to differences in the temperature to which the chrysalids are exposed. The butterfly may often be seen hovering about pawpaw bushes, upon which the eggs are deposited. The mature caterpillar is pea-green with bands of yellow and black; the chrysalis is green or brownish, and the last crop of chrysalids does not produce butterflies until the following Spring. This butterfly ranges from New England south to the Florida Keys, and west to the foot-hills of the Rockies.
Papilio cresphontes, the Giant Swallowtail, is the largest butterfly in this country, measuring nearly six inches from tip to tip. The color is dark brown with bands and blotches of bright yellow, and there is a red-and-blue spot on the inner margin of the hind wings. The under side of both wings is yellow, with narrow dark brown bands. This butterfly is very common in Florida, where the caterpillars—the natives call them orange-dogs—do a great deal of damage to the orange and lemon trees. Each female butterfly is known to lay a great number of eggs, and it has been suggested that the ravages of the orange-dog may be checked by shooting the butterflies on the wing with miniature shotguns. In recent years the species has extended its range northward, and has become quite common in the Middle West; a number of specimens have been taken in New England, and even in Canada. In the northern part of its territory there are no citrus trees, but the caterpillar feeds well enough upon prickly ash and several kinds of poplars.