Phylloxera
“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. 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.”
CHAPTER XXIII
SILK
“SOONER or later, according to its species, a day comes when the larva feels itself strong enough to face the perils of metamorphosis. It has valiantly done its duty, since to stuff its paunch is the duty of a worm; it has eaten for two, itself and the matured insect. Now it is advisable to renounce feasting, retire from the world, and prepare itself a quiet shelter for the death-like sleep during which its second birth takes place. A thousand methods are employed for the preparation of this lodging.
“Certain larvæ simply bury themselves in the ground, others hollow out round niches with polished sides. There are some that make themselves a case out of dry leaves; there are others that know how to glue together a hollow ball out of grains of sand or rotten wood or loam. Those that live in tree-trunks stop up with plugs of sawdust both ends of the galleries they have hollowed out; those that live in wheat gnaw all the farinaceous part of the grain, scrupulously leaving untouched the outside, or bran, which is to serve them as cradle. Others, with less precaution, shelter themselves in some crack of the bark or of a wall, and fasten themselves there by a string which goes round their body. To this number belong the caterpillars of the cabbage butterfly and the swallow-tail. But especially in the making of the silk cell called cocoon is the highest skill of the larvæ shown.
Silk Worm
Eggs, worm, cocoon, and butterfly
“An ashy white caterpillar, the size of the little finger, is raised in large numbers for its cocoon, with which silk stuffs are made. It is called the silkworm. In very clean rooms are placed reed screens, on which they put mulberry leaves, and the young caterpillars come from eggs hatched in the house. The mulberry is a large tree cultivated on purpose to nourish these caterpillars; it has no value except for its leaves, the sole food of silkworms. Large tracts are devoted to its cultivation, so precious is the handiwork of the worm. The caterpillars eat the ration of leaves that is frequently renewed on the screens, and from time to time change their skin, according to their rate of growth. Their appetite is such that the clicking of their jaws is like the noise of a shower falling during a calm on the foliage of the trees. It is true that the room contains thousands and thousands of worms. The caterpillar gets its growth in four or five weeks. Then the screens are set with sprigs of heather, on which the worms climb when the time comes for them to spin their cocoons. They settle themselves one by one amid the sprigs and fasten here and there a multitude of very fine threads, so as to make a kind of network which will hold them suspended and serve them as scaffolding for the great work of the cocoon.
“The silk thread comes out of the under lip, through a hole called the spinneret. In the body of the caterpillar the silk material is a very thick, sticky liquid, resembling gum. In coming through the opening of the lip, this liquid is drawn out into a thread, which glues itself to the preceding threads and immediately hardens. The silk matter is not entirely contained in the mulberry leaf that the worm eats, any more than is milk in the grass that the cow browses. The caterpillar makes it out of the materials of its food, just as the cow makes milk of the constituents of her forage. Without the caterpillar’s help man could never extract from the mulberry leaves the material for his costliest fabrics. Our most beautiful silk stuffs really take birth in the worm that drivels them into a thread.