The Collaborative International Dictionary of English v.0.48:
Silkworm \Silk"worm`\, n. [AS. seolcwyrm.] (Zool.)
The larva of any one of numerous species of bombycid moths,
which spins a large amount of strong silk in constructing its
cocoon before changing to a pupa.
Note: The common species (Bombyx mori) feeds on the leaves
of the white mulberry tree. It is native of China, but
has long been introduced into other countries of Asia
and Europe, and is reared on a large scale. In America
it is reared only to small extent. The Ailanthus
silkworm (Philosamia cynthia) is a much larger
species, of considerable importance, which has been
introduced into Europe and America from China. The most
useful American species is the Polyphemus. See
Pernyi silkworm, the larva of the Pernyi moth. See Pernyi
Silkworm gut, a substance prepared from the contents of the
silk glands of silkworms and used in making lines for
angling. See Gut.
Silkworm rot, a disease of silkworms; muscardine.