In the descriptions which we shall give of Insect Architecture, we shall employ as few technical words as possible; and such as we cannot well avoid, we shall explain in their places: but, since our object chiefly relates to the reproduction of insects, it may be useful to many readers to introduce here a brief description of the changes which they undergo.

It was of old believed that insects were produced spontaneously by putrefying substances; and Virgil gives the details of a process for creating a swarm of bees out of the carcass of a bull: but Redi, a celebrated Italian naturalist, proved by rigid experiments that they are always, in such cases, hatched from eggs previously laid. Most insects, indeed, lay eggs, though some few are viviparous, and some, like serpents, propagate both ways. The eggs of insects are very various in form, and seldom shaped like those of birds. We have here figured those of several species, as they appear under the microscope.

When an insect first issues from the egg, it is called by naturalists larva, and, popularly, a caterpillar, a grub, or a maggot. The distinction, in popular language, seems to be, that caterpillars are produced from the eggs of moths or butterflies; grubs, from the eggs of beetles, bees, wasps, &c.; and maggots (which are without feet), from blow-flies, house-flies, cheese-flies, &c., though this is not very rigidly adhered to in common parlance. Maggots are also sometimes called worms, as in the instance of the meal-worm; but the common earth-worm is not a larva, nor is it by modern naturalists ranked among insects.

Larvæ are remarkably small at first, but grow rapidly. The full-grown caterpillar of the goat-moth (Cossus ligniperda) is thus seventy-two thousand times heavier than when it issues from the egg; and

the maggot of the blow-fly is, in twenty-four hours, one hundred and fifty-five times heavier than at its birth. Some larvæ have feet, others are without: none have wings. They cannot propagate. They feed voraciously on coarse substances; and as they increase in size, which they do very rapidly, they cast their skins three or four times. In defending themselves from injury, and in preparing for their change by the construction of secure abodes, they manifest great ingenuity and mechanical skill. The figures on the preceding page, exemplify various forms of insects in this stage of their existence.

When larvæ are full grown, they cast their skins for the last time, undergo a complete change of form, and, with a few exceptions, cease to eat, and remain nearly motionless. When an insect, after this change, does not lose its legs, or continues to eat and move, it is popularly called a Nymph; and when the inner skin of the larva is converted into a membranous or leathery covering, which wraps the insect closely up like a mummy, it is termed Pupa, from its resem

blance to an infant in swaddling bands. From the pupa of many of the butterflies appearing gilt as if

with gold, the Greeks called them Chrysalides, and the Romans Aurelia, and hence naturalists frequently call a pupa, chrysalis, even when it is not gilt. We shall see, as we proceed, the curious contrivances resorted to for protecting insects in this helpless state.

After a certain time, the insect which has remained in its pupa-case, like a mass of jelly without shape, is gradually preparing for its final change, when it takes the form of a perfect insect. This state was called by Linnæus, Imago, because the insect, having thrown off its mask, becomes a perfect image of its species. Of some, this last portion of their existence is very short, others live

through a year, and some exist for longer periods. They feed lightly, and never increase in size. The chief object of all is to perpetuate their species, after which the greater number quickly die. It is in this state that they exercise those remarkable instincts for the preservation of their race, which are exhibited in their preparations for the shelter of their eggs, and the nourishment of their larvæ. The foregoing are examples of insects in the imago, or perfect state.