Page:The American Cyclopædia (1879) Volume XV.djvu/52

 SILKWORM the month has a vertical opening, with strong d serrated jaws: the stomach is very large, SwS?be expected in such a voracious lar- vl It lives exposed in the wild state, but none of the Chinese or European worms are owed to incur the risks of life m the open air According to the experiment of Count Dandolo, 100 newly hatched silkworms weigh 1 iin, after the first moult 15, after the sec- ond 94 after the third 400, after the fourth 4 628 and at full size 9,500 grains; each con- sumes an ounce of mulberry leaves during se stages, about 60,000 times its primitive weight, and its length increases from 1 to 40 lines during the same period; by calculation the product of an ounce of eggs eats upward of 1,200 Ibs. of leaves, and should furnish 120 Ibs. of cocoons. Like most other cater- pillars, it changes its skin four time-', at in- tervals depending on the temperature and on the quantity and quality of the food; if kept at 80 to 100 F. it moults in half the time re- quired at ordinary temperatures. As usually treated, the first moult takes place on the 4th Silkworm Moth, Female. or 5th day after hatching, the second begins on the 8th, the third takes up the 13th and 14th, and the last happens on the 22d or 23d day ; after this the fifth age lasts 10 days, making about 32 days for the whole process to matu rity. The appetite increases with the size til nft-r the fourth moult; during the test 10 days the silk gum is elaborated, the appetite diminishes, and the larva begins to spin its cocoon. The spinning apparatus is near the mouth and connected with the silk bags, which are long, slender, and convoluted, contain ing a liquid gum ; they are closed below, anc end above in slender tubes, one on each side which unite to form the single spinning tube the gum from which the silk is produced 01 contact with th air is elaborated by the Ion; glandular organs; every thread of silk i made np of two strands. It is customar; to supply to the worms a piece of rolle' hollow substance into whic they. or a convenient twig, for th formation of the cocoons. They first mak an outer covering of floss silk to keep off th ain within this they spin fine silk, bending 10 head and body up and down and cross- ne to every side, entirely surrounding the body 9 a protection against wind and cold ; and within this is a more delicate silk, glued firmly ogether for the inner chamber, resisting both old air and water. After building the cocoon he larva is transformed into a chrysalis, and omes forth a moth, easily bursting through he case, the silk, and the floss. The cocoon esernbles a pigeon's egg, and is from 1 to H long, and bright yellow ; the moth emerges rom it in from 15 to 56 days, according to emperature, the former being the time m the outhern United States ; 18 to 20 days is the ime in Connecticut, three weeks in France, ind five to six weeks in England ; the cocoon s made in from a few hours to three days, ind is more pointed at one end than the other ; he silk is not interwoven nor the glue applied at the pointed end, toward which the head is always placed. The chrysalis has no spines nor serrations on the edge of the abdominal rings, has a leathery skin, and the stomach illed with a yellowish nutritive fluid ; the or- gans of the moth are gradually developed, and n two or three weeks the skin of the chrysalis jives way, the moth escapes into the cocoon chamber, and readily sets itself free, leaving within the remains of its former covering. [n the wild state the cocoon is made about the middle of June. The silk from the cocoons containing males is finer and more tenacious than that from the female cocoons. It is for- tunate that the threads do not adhere as they do in the cocoons of many other larvjs, else the operation of unwinding would be very difficult if not impracticable ; even in the B. mori the silk is sometimes coarse and adherent, when the quality of the food has not been good. Like other caterpillars, the silkworm some- times makes mistakes, and two or three are occasionally shut up in a single cocoon, in which they undergo metamorphosis perfectly well. The usual way of throwing the cocoons into boiling water kills the chrysalis; but merely steaming them over boiling water softens the glue sufficiently to allow the unwinding of the silk, and permits the moth to come forth alive from the interior layer and deposit the eggs or prepare for a new brood. The whole secret in raising the silkworm consists in securing for it warmth, dryness, plenty of proper food, and pure air. The mulberry tree, the leaves of which constitute the food of the silkworm, requires for its perfect growth long continued dry and warm weather, and suffers in the rainy seasons of England and France ; it is said to have no insect feeding upon it but the lomlyx; it exhausts the earth where it is planted, as far as any other vegetation is concerned ; one tree of the M. multicaulis, it is computed, will feed as many silkworms as would produce annually 7 Ibs. of silk. Silkworms are very tender and liable to perish from slight changes of temper- ature and dampness, from foul air, and im-