Fig. 849.—Pupa.
Insects come to maturity only after undergoing successive changes from the egg to the perfect animal. The eggs (some of which are very beautiful) are first deposited in some safe place, either attached to a leaf or tied up in a small bundle by silken threads spun by the parent insect, and in some nutritious substance, so that when it comes to life it may at once have food; this is sometimes in manure, sometimes in flesh, and sometimes under the skin of a living animal (few are exempt from this infliction), where they remain for a time and then come forth as maggots, caterpillars, etc.; in this state they are called larvæ,—these are generally active creatures and eat most voraciously, which seems to be the principal act of this state of their existence. These larvæ frequently change their skins as they grow, and at last they assume the next stage of their life, the pupa or chrysalis state, which is one generally of complete inactivity; many of these larvæ weave themselves a covering of a sort of silk, to defend them while in the pupa state,—such as the silkworm, whose covering (cocoon) is the source of all the silk of commerce,—others merely place themselves in a situation of security. The pupa remains dormant for a certain time, and then becomes the imago or perfect insect (the last state of its existence), such as a moth, a butterfly, a beetle, etc. These are of different sexes, and in due time produce a batch of eggs and then die; these eggs are often incredible in numbers, amounting to many thousands—but few escape the watchful eyes of other insects and of birds who feed upon them.
But there are some of the insecta which do not undergo metamorphosis; the Aptera or wingless insects include these, as the flea and such parasites which bore into other animals, and deposit their eggs within them.
Fig. 850.—Imago.
Insects have very little means for making themselves audible, at least so far as can be ascertained. The humming of bees and flies and other insects are, of course, not intended to represent the voice. The cricket’s “chirp,” as people commonly imagine, but the sound is attributable to the rubbing together of the wings or wing-cases, as is the noise produced by the field-cricket. There is a very peculiar sound attributable to the “Death-Watch,” a ticking, and to nervous people terrible warning of dissolution. It may reassure some one, perhaps, to know that this “unearthly sound” is caused simply by the insect beating its head against a piece of wood to attract its mate, as the female glow-worm lights her lamp to guide her lord to her bower.
The Insecta may simply be divided into nine orders:—
| 1 Coleoptera. | Beetle tribe. | Case-winged. |
| 2 Orthoptera. | Locusts, crickets, etc. | Straight-winged. |
| 3 Neuroptera. | Dragon-flies, etc. | Nerve-winged. |
| 4 Hymenoptera. | Bees, ants, wasps, etc. | Membrane-winged. |
| 5 Strepsiptera. | Parasites of the foregoing. | Twisted-winged. |
| 6 Lepidoptera. | Moths and butterflies. | Scale-winged. |
| 7 Hemiptera. | Bugs, water-boatmen. | Half-winged. |
| 8 Diptera. | House-fly, gnat. | Two-winged. |
| 9 Apraniptera. | Fleas, “chigos.” | Wingless. |
| (Of these the metamorphoses of 1, 3, 4, 6, and 8 are complete). | ||
Fig. 851.—The Stag-Beetle (Lucanus cervus).