“Thenceforth it grows no larger. Just as it was on emerging from its cell, so it will remain to the end, without the least increase either in weight or in bulk. Thus it leads a very staid existence. In its grub state the famished creature gnawed wood night and day; its life was a perpetual digestion. Now, on the contrary, all that it needs in the way of sustenance is an occasional sip of the sweetened sap oozing from the bark of the tree.
“But its days of idle delight are numbered; it has scarcely a couple of months to spend joyously among the oak trees. Then it lays its eggs, one by one, in the crevices of tree-trunks, to propagate its kind; and, that done, it very soon dies. It has played its [[233]]part. From those eggs will come forth worms which will patiently work their way into the wood, hollow out galleries there in their turn, and begin all over again the very sort of existence led by their fore-fathers.
“The greater number of insects have the same life-history as the stag-beetle: they pass through different stages before taking on their final form. All without exception, the smallest as well as the largest, come from eggs deposited by the mother in chosen places where the needed nourishment, so variable in different species, is easy to find.
“From the egg emerges, not the finished insect with all its distinctive traits, but a provisional creature bearing, very often, no resemblance to the parent or to the matured offspring of that parent. This initial form we called a worm in speaking of the stag-beetle, and the name is in that instance appropriate; but in a multitude of cases it would be incorrect, having no agreement with the creature’s appearance. We then call it a larva.
“The larva is therefore the insect under the form it presents on emerging from the egg. Its continuance in this form is longer than in that of the finally perfected creature. The larva of the stag-beetle remains a larva for three or four years, whereas the beetle itself lives but a couple of months. The sole occupation of this grub is eating, continual eating, that it may grow fat and store up supplies enough to carry it through its subsequent transformations.
“Having attained sufficient size, the larva constructs [[234]]a retreat for itself, hollows out a little cell, and spins a cocoon where in perfect quiet the delicate task of transformation will be undertaken. It strips off its skin and becomes an inert, formative body known as a nymph.
“Finally, the nymph, having arrived at the right degree of maturity, casts off its wrappings and reveals itself as transformed into a perfect insect. It lays its eggs, and the same succession of changes is again repeated. The egg, the larva, the nymph, the perfect insect—there you have the four stages of the insect’s life. These changes of form are called metamorphoses.” [[235]]