“It is otherwise with insects. The swallow-tail, under its form of butterfly, is not first small, then medium, then large. When, for the first time, it opens its wings and takes flight, it is as large as it ever will be. When it comes out from under ground, where it lived as a grub, when for the first time it appears in the daylight, the June bug is such as you know it. There are little cats, but no little swallow-tails nor little June bugs. After the metamorphosis, an insect is what it will be to the end.”
“But I have seen small June bugs flying round the willows in the evening,” objected Jules.
“Those little June bugs are of a different kind. They will always remain the same. Never will they grow and become common June bugs, any more than a cat would grow into a tiger, which it resembles so much.
“The grub alone grows. At first very small on coming out of the egg, little by little it acquires a size in conformity with the future insect. It gathers the materials that the metamorphosis will use,—materials for the wings, antennæ, legs, and all those things that the larva does not have, but that the insect must have. Out of what will the big green worm that lives in dead wood, and must some day become a stag-beetle, make the enormous branched mandibles and the robust horny covering of the perfect insect? Of what will the larva make the long antennæ of the capricorn? Of what will the caterpillar make the large wings of the swallow-tail? Of that which the caterpillar, larva, and worm amass now, with thrifty hoarding of life-supporting matter.
“If the little pink-nosed cat were born without ears, paws, tail, fur, mustaches, if it were simply a little ball of flesh, and should some day have to acquire all at once, while asleep, ears, paws, tail, fur, mustaches, and many other things, is it not true that this work of life would necessitate materials gathered together beforehand and held in reserve in the fatty tissues of the animal? No thing can be made from nothing; the smallest hair of the cat’s mustache shoots forth at the expense of the substance of the animal, substance which it acquires by eating.
Goat Moth
“The larva is in precisely this case: it has nothing, or next to nothing, that the perfect insects must have. It must therefore amass, in view of future changes, materials for the change; it must eat for two: for itself first, and then for the insect that will come from its substance, transformed and, in a sense, recast. So the larvæ are endowed with an incomparable appetite. As I have said, to eat is their sole business. They eat night and day, often without stopping, without taking breath. To lose a mouthful, what imprudence! The future butterfly would perhaps have one scale less to its wings. So they eat gluttonously, take on a stomach, become big, fat, plump. It is the duty of larvæ.
“Some attack plants; they browse on the leaves, chew the flowers, bite the flesh of fruit. Others have a stomach strong enough to digest wood; they hollow out galleries in the tree-trunks, file off, grate, pulverize the hardest oak, as well as the tender willow. Others, again, prefer decomposed animal matter; they haunt infected corpses, fill their stomachs with rottenness. Still others seek excrement and feast on filth. They are all scavengers on whom has developed the high mission of cleansing the earth of its pollution. You would sicken at the mere thought of these worms that swarm in pus; yet one of the most important services, a providential service, is rendered by these disgusting eaters which clear away infection and give back its constituent elements to life. As if to make amends for its filthy needs, one of these larvæ will later be a magnificent fly, rivaling polished bronze in its brilliancy; another, a beetle perfumed with musk, its rich coat vying with gold and precious stones in splendor.
