The untutored savage, throughout all time, has clothed himself with the skins of mammals, and adorned his person with the feathers of birds, but it would never dawn upon him to look for his clothing to the insect race. That to him would appear an absurdity, and yet silk, the most beautiful of all fabrics, is the product of an insect-the silk-worm.
The silk-worm is the grub or caterpillar of a peculiar kind of moth, which feeds on the leaves of the mulberry tree. The moth came originally from China. It has a thick-set, hairy body, with short, stout legs and large cream-colored wings marked with dark stripes. The female is bigger than the male, and altogether different in appearance. She dies as soon as she has laid her eggs, which are smaller than grains of mustard-seed, and from 250 to 400 in number; the male does not long survive her.
The favorite food of the silk-worm, as we said just now, is the leaf of the mulberry tree. People, therefore, who rear silk-worms provide a constant supply of fresh mulberry leaves, and the mother-moth lays her eggs on the leaves. The grub, when hatched, emerges from theegg in the form of a little black worm, not more than a quarter of an inch in length, but there is plenty of food at hand, and it feeds and grows quickly. While growing it casts its skin as it becomes too small, and another skin takes its place. During its growth the silk-worm moults,or casts its skin, four times. The first moult takes placeabout eight days after it leaves the egg; the second, third, and fourth at regular intervals of about five days each.
After the last moult it feeds voraciously on the mulberr y lea vesand continues to grow for about ten days longer, when it may be said tohave reached its full size as a caterpillar. It is thenabout 2 inches long; its body, which
is of a grayish cream color, is supported upon sixteen legs, and consists of twelve ringed segments, from the last of which projects a sort of horn. It now ceases to feed, and after fixing itself to some light object, such as a twig, a bit of straw, or a piece of paper rolled up, it commences to send out, from two small holes under its jaw, a fine, yellow, gum-like substance, which hardens into a silky thread or fiber on exposure to the air. With this the worm completely envelops itself as in a ball.
The first day is usually spent in forming a loose, flossycovering for the outside of the ball. This it afterwards coats with gum, so as to make it into a kind of outer skin. Inside that, during the next three days, the silk-worm spins a firm ball of fine, strong, yellow fiber, which is the silk of commerce. The whole forms an oval ball, about thesize of a walnut, and is called a cocoon.
The creature-whatever it is-of course occupies the center of the cocoon. It is not a silk-worm, it is not a moth. It is a lumpy, oval ball, covered with a dark red, shiny skin or shell; but if it were removed from the cocoon, it would be to all appearance lifeless. It is the silk-worm chrysalis. It has taken the first stage of that wonderful change, which is peculiar to the life-history of all insects-from the grub to the pupa or chrysalis, and if left alone it would pass from the pupa to the perfect insect.
