The Lepidoptera undergo a complete larval metamorphosis, and the process is more familiar to general readers than in the case of other insects. From the eggs, which are often objects of great beauty when examined through a lens, are hatched wormlike creatures that grow rapidly by repeated moltings of the skin into full-sized "caterpillars"; those of certain moths develop in community nests, but ordinarily they live singly. All have three pairs of thoracic legs, and a variable number of temporary "prolegs" near the rear of the body. Caterpillars may be smooth, round, and colorless, or coated with a heavy fur, or bristling with knobs, tufts of hairs, and other appendages, and brightly ornamented with color; and many of these peculiarities appear to be wholly defensive in purpose. Some caterpillars give off, when alarmed, disgusting and acrid fluids, and the hairs of others irritate venomously the skin of anyone handling them, and probably account for the fact that few birds will touch certain species. All caterpillars feed voraciously—in fact, this is the only time in the life of many species when food is taken, the adult moths and butterflies as a rule being neither willing nor able to eat. At a certain time, having completed its final molt, the caterpillar arranges itself according to the custom of its race, and subsides into a pupa.
| CATERPILLAR OF THE MILKWEED BUTTERFLY |
| (Anosia plexippus.) (Smithsonian Institution.) |
A century ago men interested in butterflies spoke of themselves as aurelians, explaining that "aurelia" was a proper name for the butterfly pupa because of the golden ornaments it usually bore. Really, however, this characteristic, so marked in the gilt "buttons" of our common milkweed butterfly, pertained to only a single family—the Nymphalidæ. When the nymphalid caterpillar reaches the turning point, it withdraws the abdomen a little from the cracking skin, exudes a little sticky silk which it fastens to its support, then hooks the tip of its abdomen firmly into this silk; this done, hanging thus by its tail, the caterpillar finally shakes off its coat and, as a chrysalis (a Greek word of the same general sense as the Latin aurelia) the pupa hangs, head down and inert, until the following spring.
The butterflies of greatest size and most splendid coloring belong to the family Nymphalidæ, whose hundreds of species are scattered all over the warmer parts of the world. Here belong those gorgeous tropical ones, whose wings, sometimes with a spread of five inches, emulate the prismatic hues of the "eyes" in a peacock's tail, and which are so often seen mounted as lovely ornaments in curiosity shops; and here also is classified that strange "leaf butterfly" of Malaysia, whose wings when closed so perfectly imitate a leaf of the tree on which it alights that the sharpest eyes can hardly find it. Here, too, belong our brown-streaked "fritillaries," such as the vanessas, and darker ones like our mourning cloak, and many others well known to amateurs.
| FINAL MOLTING OF A NYMPHALID CATERPILLAR |
| (a) Before shedding skin. (b) In act of shedding skin. (c) Trying to catch hold of silk button. (Smithsonian Institution.) |
All of this family have their chrysalides hung by the tail; but in the remainder of the butterfly families they are held in an upright position by a loop of silk that passes around them like a girdle. Such are the "coppers," the "blues," the "hair streaks" and many other small, gayly colored species (Lycænidæ) common in summer, to which season they add so beautiful an interest. In another large family, the Papilionidæ, are found the great yellow and black "swallowtails," which are almost exclusively American, and several dark blue or purple-marked species, with "tails" to their wings, that attract the attention of the most careless as they lazily flit among the flowers. In this family, too, are the sulphur-yellow butterflies that dance over the roads and fields in little flocks; and, alas, the white ones whose caterpillars are so injurious to cabbages and similar vegetables. The last family (Hesperidæ) contains small, rather obscurely marked, butterflies that connect the Rhopalocera with the Heterocera, or moths.