The Story Book of Science  by Jean Henri Fabre

The Big Eaters

"I NSECTS propagate themselves by eggs, which they lay, with admirable foresight, where the young will be sure to find nourishment. The little creature that comes from the egg is a larva, a feeble grub, which, most often, has to shift for itself, procure at its own risk food and shelter—the most difficult thing in this world. In these painful beginnings it cannot expect any help from its mother, dead some time before; for in insect life the parents generally die before the hatching of the eggs that produce the young. Without delay the little larva sets to work. It eats. It is its sole business, and a serious one, on which its future depends. It eats, not only to keep up its strength from day to day, but above all to acquire the plumpness necessary for its future metamorphosis. I must tell you—and this perhaps will surprise you—that an insect ceases to grow after attaining its final perfect form. It is known, too, that there are insects—among others, the butterfly of the silkworm—that do not take any nourishment at all.

"A cat is at first a tiny little pink-nosed creature, so small that it could rest in the hollow of the hand. In one or two months it is a pretty kitten that amuses itself at a mere nothing, and with its nimble paw whips the wisp of paper that one throws before it. Another year, and it is a tom-cat that patiently watches for mice or joins battle with its rivals on the roof. But, whether a tiny creature hardly able to open its little blue eyes, or a pretty playful kitten, or a big quarrelsome tom-cat, it has always the form of a cat.

"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 swallowtail? 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.

"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.

Goat Moth

"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.

"But these larvæ devoted to the work of general sanitation cannot make us forget other eaters, of whom we are victims. The grubs of the June bug alone sometimes multiply so rapidly in the ground that immense tracts are denuded of vegetation, which is gnawed at the roots.

Phylloxera

The forester's shrubs, the farmer's harvests, the gardener's plants, just when everything seems prosperous, some fine morning, hang withered, smitten to death. The worm has passed that way, and all is lost. Fire could not have committed more frightful ravages. A miserable yellow louse, hardly visible, lives under ground, where it attacks the roots of the grape vine. It is called phylloxera.  Its calamitous breed threatens to destroy all our vineyards. Some grubs, small enough to lodge in a grain of wheat, ravage the wheat in our granaries and leave only the bran. Others browse the lucerne so that the mower finds nothing left. Others, for years, gnaw at the heart of the wood of the oak, poplar, pine, and divers other large trees. Others, which turn into those little white butterflies flying around the lamp in the evening and called moths, eat our cloth stuffs bit by bit, and finish by reducing them to rags. Others attack wainscoting, old furniture, and reduce them to powder. Others—But I should never get through if I were to tell you all. This little people to which we often disdain to pay the slightest attention, this little race of insects, is so powerful on account of the robust appetite of its larvæ, that man ought seriously to reckon with it. If a certain grub succeeds in multiplying beyond measure, whole provinces are threatened with the tragic fate of starvation. And we are left in perfect ignorance on the subject of these devourers! How can you defend yourself if the enemy is unknown to you? Ah, if I only had the management of these things! As for you, my dear children, while waiting for our talks to be resumed with more detail concerning these ravagers, remember this: the larvæ of insects are the great eaters of this world, the providential demolishers that finish the work of death and thus prepare for the work of life, since everything or nearly everything passes through their stomach."