Caterpillars are able to grow by sloughing the skin. which from time to time cracks, en abling the creature to crawl out of it, and to begin another period of growth with a new and elastic skin that has formed beneath the old one. Four or five of these molts take place as a rule. When the larva is to hibernate, it usually does so after the first or second molt, and resumes feeding and growth when it wakes up in the spring.
One great distinction between moths and butterflies lies in the form and structure of the pupa — that quiescent stage of development in which the caterpillar is transformed to the imago. The term chrysalids is usually applied to the pupa of butterflies, because no such a cocoon as is common among moths enwraps them. They are naked and hang free from the underside of some support, as a twig or stone, or are suspended against a surface, as the bark of a tree-trunk, attached to a "button" of silk, and held in place by a girdling thread of silk. Chrysalids are usually protectively colored.
The families of butterflies are few, and all of them, except one small tropical group (Libytheidw) are represented in every conti nent Following is a list of the five families recognized by American entomologists, begin ning with the most primitive and ending with the most specialized: (1) Hesperiidm, (2) Papi lionidie, (3) Lyccenida, (4) Lemoniidw, (5) Nymphalida. In the last three families, which comprise the majority of butterflies, the first pair of legs is more or less modified, differing from the two hinder pairs, especially in the male nymphalids, in the more or less aborted tarsi, or toe-joints.
The Hesperndw, or "skippers," have a world wide range except New Zealand, and are largely represented in the United States. This family contains small, prevailingly brown but terflies, with relatively large bodies and broad heads, the feelers hooked at the tip. The fore wing is triangular and pointed in shape, and the prevailing color is brown. The hesperiids are remarkable for their short, jerky flights. The pupa is enclosed in a light, silky cocoon.
The Papilionidw are a very populous family of large and handsome butterflies, familiarly called swallowtails" from the prolongation of the hind wing in many of them. Yellow is a prevailing color, usually ornamented with black, red-brown or some other dark tint. The wing-neuration differs characteristically from that in other families. All six feet are present in both sexes. The caterpillar is cylindrical, elongate and never hairy, but often tuberculate, and is provided with a retractile tentacle behind the bead, which in some species emits a highly disagreeable odor of protective value. The pupa has two anterior projections
called and hangs to its food-plant by its anal extremity, sustained by a loose girdle. This family is distributed throughout the world.
The Lycanide are a very large family of small or moderately sized butterflies with slender bodies, the feelers placed close together, and the front feet aborted in the males. The caterpillars are short and hairy, resembling woodlice in shape. The pupa has a well marked "waist," is clothed with hairs or bristles, is attached to a pad of silk by the cremaster and is girdled with a silken thread. This family occurs in all parts of the world, and its members are known, on account of their prevailing hues, as "blues," "coppers" and "hair-streaks." In alighting they always fold their wings upright.
• The Lentoniidcr are a small family related to lymnids, which contains brilliant butterflies mostly confined to tropical America, a few bright-brown species, the "metal-marks" of the subfamily Erycinince, occurring in the south western United States.
The Nymphalida embrace a group called "four-footed)" or Thrush-footed" butterflies, be cause the foremost pair of feet in both sexes are dwarfed, hairy and held folded up against the body, This is the largest and most promi nent of butterfly families, is very ancient and is much subdivided in classification. The caterpillars vary much in form, and some are hairy, or armed with spines or tubercles. The pupa hangs by its "tail," but is not sustained by a silken girdle-thread. The nymphalids are represented in all countries, but most numer ously and strikingly in tropical America.
Chapman, T. A.,
of Moths' (in (Transactions) of the Entomological Society, London 1893) ; Doubleday and West wood, (Genera of Diurnal Lepidoptera> (ib. 1862) ; Edwards,