“I can’t think without horror,” said Jules, “of the terrible itching such an army of vermin must cause, biting and boring into the creature’s flesh all over its body.”
“Your horror would redouble if you knew that this vermin only awaits a favorable opportunity to emigrate to our bodies even, and to ravage us in our turn.”
“What! Those horrid pig worms have designs on us?”
“And designs, alas, too often accomplished, if we are not careful. That is what we are now about to consider.” [[342]]
CHAPTER XXXVI
A PERSISTENT PARASITE
“Many members of the animal kingdom change their form in the course of their existence, and with the new structure adopt also a new way of living. Thus the caterpillar and the butterfly, for example, are in reality the same creature, but very different in shape and habits. The caterpillar drags itself heavily over the plant, gnawing the foliage; the butterfly, furnished with light and graceful wings, flies from flower to flower, imbibing a sugary liquor from each with its long proboscis. The cherry worm grows in the midst of the juice that feeds it; after attaining full size it falls from the tree with the damaged fruit and hastens to bury itself in the ground, there to undergo its transformation. Next spring it comes forth in the form of an elegant fly that lives on honey from the flowers and never again touches a cherry except to deposit its eggs therein, one by one. In the same way, again, the nut worm, after finishing its growth, bores a hole in the firm shell, emerges from its fortress, and buries itself for a time in the soil. There it becomes a beetle with a long proboscis, the so-called nut weevil, which leaves its subterranean retreat in the spring and takes up its quarters on the foliage of a [[343]]nut tree, where it lays its eggs in the growing nuts.
“All species of animal life that change their shape act in this way. In the first half of their existence, under their initial form, they have certain habits and certain dwelling-places; in the second half, under their final form, they have habits and abodes that are quite different.
“Well, the worm that makes its home in the white cells or granules of the diseased pig’s flesh is also subject to transformation. It has to change its form, but before doing so it must first change its abode. The cherry worm would never turn into a fly so long as it remained in the cherry; the nut weevil would never become a beetle if it continued to abide in the nut. Both must emigrate and hollow out a home for themselves in the earth if they would cease to be worms and become a fly in one case, a beetle in the other. In like manner, the parasites of the diseased pig would never attain their final form in the flesh that they inhabit; it is absolutely necessary for them to change their abode in order that the transformation may take place. But as they cannot leave their cells of their own accord and transport themselves to their new abode, which is difficult of access, as you will see, they wait patiently, whole years if necessary, for a favorable opportunity to emigrate.”