In the American classification of the Lepidoptera, the Bombycidæ occupy a place between the Zygænidæ and the Noctuidæ. They include a large number of genera and species, and are well represented on this continent. The principal characteristic of the family is that from which it derives its name of Bombycidæ,—or spinners,—the power the caterpillars have of producing a silken fibre, which they use in spinning a cocoon in which to pass the pupa stage of their existence. The Silk-worm moth, Bombyx mori, is the typical species of the family. Some genera, however, do not produce silk in any quantity. They are also remarkable as a family for the imperfectly developed mouth parts in the perfect insect. In nearly all of them the tongue is short, and in some species wanting, and the other parts of the mouth so imperfect that it is not probable the insects feed at all in the perfect state.