The Nymphalidæ may be distinguished from all other butterflies by the fact that in both sexes the foremost, or prothoracic, pair of legs is greatly dwarfed, useless for walking, and therefore carried folded up against the breast. This is the largest of all the families of butterflies and has been subdivided into many subfamilies. Some of the genera are composed of small species, but most of them are made up of large or medium-sized forms. To this family belong many of the most gorgeously colored butterflies of the tropics, among them the brilliant blue Morphos of equatorial America.

The caterpillars, when they emerge from the egg, have heads much greater in diameter than the rest of their bodies. In the earlier stages the bodies taper from before backward, and are adorned with little wart-like protuberances, which bear hairs. In later stages these little protuberances in many genera are replaced by branching spines and fleshy projections, which impart to the caterpillars a forbidding appearance. The mature caterpillar generally has a cylindrical body, but in the subfamilies, Satyrinæ and Morphinæ, the larvæ are thicker at the middle, tapering forward and backward.

The chrysalids, which are generally marked by metallic spots, always hang suspended by the tail, except in the case of a few arctic species, which are found under a frail covering composed of strands of silk woven about the roots of tufts of grass, under which the larva takes shelter at the time of pupation.

In the region with which this booklet deals all the butterflies belonging to the Nymphalidæ fall naturally into one or the other of the following subfamilies: (1) the Euplœinæ, or Euplœids; (2) the Ithomiinæ, the Ithomiids; (3) the Heliconiinæ, the Heliconians; (4) the Nymphalinæ, the Nymphs; (5) the Satyrinæ, the Satyrs; (6) the Libytheinæ, the Snout-butterflies.

KEY TO THE SUBFAMILIES OF THE NYMPHALIDÆ OF TEMPERATE
NORTH AMERICA

I. With the veins of the fore wings not greatly swollen at the base.
A. Antennæ naked, not clothed with scales.
(a) Fore wings less than twice as long as broad Euplœinæ.
(b) Fore wings twice as long as broad and often translucent,the abdomen extending far beyond the inner angle of the hind wings Ithomiinæ.
B. Antennæ clothed with scales, at least above.
(a) Fore wings at least twice as long as broad Heliconiinæ.
(b) Fore wings less than twice as long as broad.
1. Palpi not as long as the thorax Nymphalinæ.
2. Palpi longer than the thorax Libytheinæ.
II. With some of the veins of the fore wing greatly swollen at the base Satyrinæ.

Subfamily EUPLŒINÆ
(The Euplœids).

Large or medium-sized butterflies; fore wings somewhat produced at apex; hind wings rounded, never with tails; fore legs greatly atrophied in the males, somewhat less so in the females; hind wings of the males marked with one or more sexual brands which in the American species are located on or near the first median nervule; some of the oriental species are white, many are dark brown or black in color, shot with purple and violet; all of the American species are of some shade of reddish brown or fulvous, with the apex of the fore wings and the outer borders of both fore and hind wings margined widely with darker color, and the veins and nervules also darker, standing out in bold relief upon the lighter ground-color; the apex of the primary and the outer border of the secondary wings are more or less spotted with light color, often with white.

The adult caterpillars are cylindrical in form, adorned with long fleshy filaments, and with their bodies of some light shade of yellow or green banded with darker colors. The American species feeds upon the plants belonging to the family of the Asclepiadaceæ, or Milkweeds.

The chrysalis is smooth, pale in color, often ornamented with metallic spots, usually golden.