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Silkworm. A term applied to the larvae, or caterpillars, of several species of moths. The common silkworm moth, Bombyx mori, is the most important of the silk-producing moths, and is a native of China, where it has been cultivated from a remote period. The mature insect is of a cream color with two or three faint brownish lines across the fore wings. The caterpillar (silkworm) when first hatched is black or dark gray, becoming lighter each time it sheds its skin and cream colored after the last molt. It feeds upon the white mulberry, and will also eat the black mulberry, the Osage orange, and lettuce, but the silk produced by larvae fed on the latter is of an inferior quality, The silk is produced in a pair of specially-constructed vessels which contain a gelatinous substance, and become much enlarged at the time when the animal is about to spin. These silk organs unite at the mouth to form a common duct termed the spinneret; through this tube the semi-fluid substance is ejected, and on coming in contact with the air hardens into the soft fiber which is so largely used in commerce. The caterpillar employs the silk in constructing a cocoon in which it assumes the pupa state. The pupa is usually killed by heating gently in an oven, because the natural exit of the moth is injurious to the silk. The Japanese oak-feeding silk-moth produces a green cocoon, the silk of which is much used for embroidery. Another species inhabits northern China and is also an oak-feeder. Its cocoon is large and grayish-brown in color. Philosamia cynthia, the Ailanthus silkworm of China and north Asia, manufactures a gray cocoon, from which the Chinese manufacture a silk recognized by its soft texture. From the cocoon of the Indian or "tussur moth," the natives manufacture the tussur silk fabric. There are several other varieties of silk-producing moths, but they are less notable and commercially unimportant.

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