The silk worm is a very valuable insect: it is produced from an egg of a yellowish colour, about the size of a small pin's head, that is laid by a moth, or butterfly. The above cut represents a male and female, and her eggs, of which she lays several hundreds: the moths live but a few days; they never eat, and die directly after the eggs are laid.

This cut shews the appearance of the worm, which at first is very small and black. Its food is the leaves of the white mulberry: as it grows in size, at four different periods, it apparently sickens, and changes its skin, and finally, when full grown, it spins a ball of silk, called a cone, or cocoon, the thread of which is about three hundred yards long: in the centre of this ball the worm entombs itself, and experiences a change to a state called an aurelia, or chrysallis, as seen below the ball: from this aurelia, the moth that lays the eggs is hatched, and thus goes on the round of this animal's changes, or transmigrations.

They are natives of China, and were brought into Italy, above twelve hundred years ago; from thence into Spain; afterwards into France; much later into Germany and the northern countries; and some have been reared in the United States of America.