Silk is the production of a species of Moth, called the _Phalæna mori_ or Mulberry moth, and its original locality, as we have already stated, appears to have been China or Persia. The changes that butterflies or moths undergo, having already been described at page 212 of Vol. II., it will be needless to repeat them. The substance which the animal spins to protect itself when in the Pupa state, is the silk, which, before it is dyed or bleached, is of a bright yellow colour more or less inclining to orange. The Silk-worm in not the only creature that produces substances of this description, for many other kinds of butterflies and moths do the same; a kind of silk has also been manufactured from the webs of spiders, and as they require less attention than the Silk-worms, the plan might have answered, had it not been for the ravenous appetites of the little spinners, who, when brought together in any quantity very speedily devour each other. Certain shell-fish also produce a kind of silky thread; as, for instance, the muscle, but more particularly the _pinna_, a large kind of shell-fish found in the Mediterranean and other seas.
The time that elapses while the silk-worm is undergoing its changes, varies according to the warmth of the weather, and the quantity of nourishment with which it is supplied; the Chinese, who are very particular on this head, take the greatest pains to supply the little creature with food, as on this they say depends the quantity of silk which the worm will produce. They calculate that the same number of insects, which would, if they had attained their full size, in from twenty-three to twenty-five days, produce twenty-five ounces of silk, would only yield twenty ounces if their growth occupied twenty-eight days, and only ten ounces if forty days. During the first twenty-four hours of the creature's existence, the patient Chinese feeds the objects of his care forty-eight times, or once every half hour, and during the second day and night thirty times, and so on, reducing the number of meals as the worms grow older; the care bestowed on their culture, and the numerous precautions taken to preserve them clean and warm, are curiously expressed in the following extract from on old Chinese work on the subject.