Page:The New International Encyclopædia 1st ed. v. 03.djvu/828

* BUTTERFLIES. 734 or tropical season of drouth. Their membranous shells take various forms, and are often exceed- ingly beautiful when seen tliTough the iiiiero- scope. "Some," says Holland, "are spherical. BTTTTEKFLIES. scope., . . others hemispherical, conical, and cylindrical Some are barrel-shaped, others have the shnpe of a cheese, and still others have the form of a turban. Jlany of them are angled, some de- pressed at the" ends. Their surface is variously ♦ ornamented. Sometimes they are ribbed. . . [and] between these ribs there is freqtienlly found a fine network of raised lines variously arranged. ... As there is great variety in the form of the eggs, so also is there great variety in their color. Brown, blue, green, red, and yellow eggs occur. Greenish or greenish white are common tints. The eggs are often ornamented with dots and lines of darker color. . . . Fertile eggs, a few days after they have been deposited, frequently undergo a change of color, and it is often possible with a magnitying- glass to see through the thin shell the form of the embryo which is being developed within the egg." The eggs may hatch in a few days or only after mouths, for numerous species pass the win- ter or the dry season in the egg. The larva which is born "in the egg, and which escapes by an opening, of curious structure, at the upper end of the shell, called the micropyle, is known as a caterpillar. This larva, or 'caterpillar,' is a worm-like creature, and takes a form, color, etc., character- istic of its group and si)ecies. The term properly is restricted to lepidopterous larvie alone, though sometimes applied to other larva>. as those of the saw-flies. The head of the caterpillar is con- spicuous, often large, and composed of horny (chitinous) material, taking various shapes. It is provided with six simple eyes (ocelli), usu- ally to be seen only with the aid of a lens, which are either just above each mandible, or on each side of the head: there are two rudimentary an- tenna!. The mouth is adapted for tearing, cutting, and masticating the substances on which the cateri>illar is destined to feed, which are very various in the different species, although in all extremely difl'erent from the food of the perfect insect: "it is provided with strong ujjper and lower jaws: a labium, or lower lip: and four palpi. In the mouth (labium) also is situated the spinneret of those species which, when they chanse into the chrysalis, envelop themselves in silken cocoons. (See Silk.) The first three seg- ments of the body are each furnished with a pair of short legs,, which are hard, scaly, and clawed, and represent the six legs of the jierfect insect: some of the remaining segments are also furnished with short feet (prolegs), varying in all from four to 10 in number, the last pair sit- uated at the posterior extremity of the body : but these are membranous or fleshy, and armed at their extremity with minute hooks. Those caterpillars in which the prolegs (which are shed in the last molt) are pretty equally dis- tributed along the body, nu)ve by a sort of regu- lar crawling motion; but those which have only four such feet, near thfe posterior extremity, move by stretching the body out to its full length, tak- ing hold by their fore feel, and then bending the body into'an arch, thus bringing the hind feet forward, when the body is stietclied out again for a new step, and so on; this last is the method of progression of the geometrid moths, called loopers, inch-worms, or measurers. The larva appears to guide itself by its feelers (palpi). The heads of many caterpillars also have de- fensive spines, or arrangements for emitting noisome liquids or odors, to be referred to later. The body of the caterpillar contains nearly all the organs of the adult butterfly or moth. Respiration goes on through nine spiracles on each side, two on each ring, except the second, third, and last. There are no external traces of sexual organs, but there arise, during this stage, the 'imaginal disks,' which develop into the wings and legs of the adult insect. These rudiments of wings exist even in very young caterpillars as a thickening and bagging in of the hypodermis. Into this bag, trachea and blood make their waj-. ,Iust how these intewial wings reach the outside is not known ; probably by the destruction of the outside hypodermis. If the wing-membrane breaks during development, so that the blood or lueniolyniph exudes, the injured wing will lie smaller or deformed. Sometimes the wings fail to expand pro)ierly because they dry too soon, and a wet sponge under a bell-jar, with trans- forming Lepidoptera, will aid in the production of perfect specimens. Feeding Habits and Mischief. — Caterpillars find themselves at birth in contact with propei food, and begin at once to devour it. and to obev certain other instincts necessary to their life and prosperity. This is the stage in which the but- terfly or moth gets most of its nourishment and growth, none taking food in the next or pupal stage, and many not feeding at all, as imagos.' The gi-eat majority are vegetable-eaters, many being limited to a particular kind of plant, or to a few nearly allied plants. Some feed on flowers, some on seeds, some on roots, and some even on the wood}' portions of stems; some on wool, hides, furs, and other animal substances ; a few on lard, and other kinds of fat. Some feed in the dark, and some in the light. Some kinds seem to eat almost incessantly, but most of them have alter- nate periods of ravenousness and quiescence. .s many of the favorite food-plants have been cul- tivated by civilized man. and other sub.stances eaten by these creatures have been made use of by him, he has multiplied by his' operations the supply and consequently tl»e numbers of certain species until they have become pests, destructive of his work and ]>rofits. It is in the caterpillar stage that almost all the dcstructiveness of the l^epidop- tera is acconnilished. On certain years they suc- ceed in denuding whole forests or many fields. The cutworm, the army-worm, and the cottnn-worm are well-known pests. Their voracity is remarka- ble. .-Vccording to Trouvelot, when a Polyijhemns caterpillar hatches, it weighs one-twentieth of a grain, and when it is 50 days old. it weighs 207 grains, and has consumed 120 oak-leaves, weigh- ing three-fourths of a pound. "So the food taken V)v a single silkworm in 56 days equals in weight 8G.000 times the primitive weight of the worm. What a destruction of leaves this sin- gle species of insects could make if only a one- hundredth jiart of the eggs laid came to matur- ity! A few years would be sufficient for the propagation of a number large enough to devour all the leaves of our forests." Taken as a whole, caterpillars are economically 80 injurious that were it not for the gieat de- pletion of their numbers by their multitudinous