If the silkworm were gifted with a desire for shifting its position much at the beginning of the work it could never inclose itself iu cocoon ; but by its mode of proceeding, as above explained, it incloses itself in a cocoon which only consumes as much silk as is necessary to hold the chrysalis.
During the time of spinning the cocoon the silkworm decreases in length very considerably, and after it is completed, it is not half its original length ; at this time it becomes quite torpid, soon changes its skin, and appears in the form of a chrysalis. The time required to complete the cocoon is about five days. In the chrysalis state the animal remains from a fortnight to three weeks ; it then bursts its case and comes forth in the imago state, the moth having previously dissolved a portion of the cocoon by means of a fluid which it ejects.
The moth is short-lived ; the female, in many instances, dies almost immediately after she has laid her eggs; the male survives her but a short time.
The silkworms, which are most extensively reared for the purpose of producing silk [SILK, in ARTS AND Sc. Div.], are liable to many
diseases, and none have been more destructive than that called muscardine. This disease attacks the caterpillar when about to enter the chrysalis state. It is always attended with the development within the body of a minute fungus closely resembling our common mould. It is probable the fungus only attacks those worms which are predisposed to disease, but in certain seasons this fungus has been so extensively developed as to lead to the supposition that it produces the disease itself. It is very certain that, when this fungus is prevailing and its spores are introduced into the body of the silk worm, it becomes rapidly diseased and dies. The fungus spreads internally before the death of the worm and afterwards it shoots forth from the surface of the skin. The chrysalis and moth will have the disease if inoculated with the fungus, but it only occurs sponta neously on the caterpillar.