Fig. 5.—Black carpet beetle: Larval skin showing the typical shape of the larva and the long tuft of bristles at the end of the body. Greatly enlarged.
Fig. 6.—Black carpet beetle: Ventral view of pupa. Greatly enlarged.
The larva.—The golden brown larva, with short, stiff body hairs, and its long tuft of hairs at the end of the body ([Fig. 5]), attains a length of one-fourth of an inch, exclusive of the tuft of hair at the end of the body. When first hatched it is almost microscopic in size, but increases rapidly under favorable food and climatic conditions. As it grows it sheds its skin from five to eleven times, and possibly oftener. This is of interest, for frequently the cast skins are mistaken for the insect itself, thus unnecessarily alarming the housewife concerning the abundance of this carpet beetle. It required approximately one year for larvæ to become fully grown when fed upon casein. Larvæ hatching during early June and fed upon casein became full grown and transformed to the adult stage during the following April, May, and June. Larvæ fed upon woolen cloth and silk and flour and meal were still only partially grown at the end of one year, indicating that the black carpet beetle may require two years for its development. In India it has been found that certain of these larvæ may require from one to three years for growth.
Fig. 7.—The varied carpet beetle: Dorsal view. Greatly enlarged.
The pupa.—In the pupa stage the insect is white, clothed with fine white hairs ([Fig. 6]), and helpless. The pupa stage continues from 6 to 16 days during early summer at Washington, D. C, and is seldom found at any other season of the year.