BUTTERFLY, one of the day-flying Lepi doptera of the sub-order Rhopalocera (compare Morn). This group is distinguished from the moths by the slender, knobbed antenna, which are never hairy or pectinated. The body is small, but there is a greater equality in the size of the three regions (head, thorax and abdomen) than in the moths, the abdomen being much shorter and smaller, as a general rule, than in the lower families of Lepidoptera. The ocelli are usually wanting; the spiral tongue is long, and the broad wings are carried erect when in repose, and are not held together dur ing flight by a bristle (frenum) and socket as in most of the moths.
The caterpillars (larva) vary greatly in shape and in their style of ornamentation, but they uniformly have, besides the thoracic legs, five pairs of abdominal legs. The pupa is called a or ((aurelian,* from the bright golden hues that adorn it in many species, but disappear as the wet tissues beneath the pupa-skin harden, just before the fly appears. A few species, such as those of the genus Vanessa, hibernate, while several species, such as V. antiopa, are social as young larva. But terflies also occasionally swarm while in the perfect state, such as species of Colias, Cynthia and Danais, multitudes of which are sometimes seen passing overhead in long columns. One of the North American species, and others else where, are migratory, flying southward in autumn.
Butterflies are found in all parts of the world except the coldest, wherever plants exist suitable for food for the caterpillars, but they are most numerous both in species and in indi viduals within the tropics, and especially in South America. About 13,000 species have been described, and it is believed that twice or three times this number are in existence. About 1,000 species inhabit North America. Butter flies are especially liable to local variation, and to seasonal and dimorphic changes, so that entomologists have recorded many sub-species and temperature-forms.
Certain Nymphatidce have glands at the end of the body secreting a repulsive fluid (see Minion') ; in others there are remarkable dif ferences between the sexes; in certain butter flies (Androconia) some of the scales are battledore-shaped, and secrete a special odor.
The species of Ayeronia, a South American genus, make a clicking noise when flying. While caterpillars are plant-eaters, those of several Lycamdw are known to be carnivorous, feeding on plant-lice and scale-insects.
The eggs of butterflies have a membranous shell, and exhibit much variety in form and character of surface. °Sometimes' says Hol land, ((they are ribbed. Between these ribs there is frequently found a fine network of raised lines, variously arranged. Sometimes the surface is covered with minute depressions, sometimes with a series of minute elevations variously disposed."' The color is most often greenish white, but many are brightly colored, or have lines and dots of color. Another peculiarity is the minute opening (micropyle) in every egg, by which the spermatozoon may enter. The eggs are laid by the female on a plant that will afford suitable food for the caterpillar when it hatches. They may be de posited singly or in small or large masses; and those that will not hatch until after the follow ing winter are protected in some way, as by a varnish, or otherwise, against the weather. Some butterflies are others lay eggs twice or more in a season, the early layings hatching quickly and the last lot sur viving the winter to establish the species in the succeeding spring. Few adult butterflies survive the advent of the cold season in the North, the species continuing through the sur vival of eggs, larva or pupa, the last some times by burial in the ground.
The caterpillars of butterflies are typically cylindrical and worm-like in form; but some are short and slug-shaped, or irregular in out line. The head is distinct, often large and formed of hard (chitinous) material; and often it bears horn-like projections or protrusile appendages. The thin skin is in many cases brightly ornamented with colors similar to those worn later by the . adult fly (imago) ; but green and gray prevail — tints inconspicu ous among the leaves and grasses on which most of the species feed. Most caterpillars live solitary lives; but in some species they are gregarious, and even weave large silken dwell mg-places in which they live as a colony.