Seasonal history.—Since the greater part of the life cycle is passed in the larva stage, the facts previously mentioned indicate that the black carpet beetle may have only one generation each year, although it may require two or three years for the same development. From the observation of the writer, made in houses, warehouses, and in the laboratory at Washington, there seems little doubt that a very large percentage of the insects have one generation each year. Farther north, or under less favorable climatic and food conditions, a generation may require two or even three years. At any rate, the adults are on the wing during early summer and the eggs for new infestations are laid then.
THE VARIED CARPET BEETLE.[6]
[6] Anthrenus verbasci L.
The varied carpet beetle is similar in shape to the common carpet beetle,[7] but is a trifle smaller. It is called the "varied" carpet beetle because the color pattern on the back of the beetle varies considerably with the arrangement of the white, brownish, and yellowish scales. [Figure 7] presents a common arrangement of the scales. The underside of the body is thickly clothed with white scales. This insect is a European pest now well established in widely separated parts of the United States. It has been found more often perhaps feeding upon seeds in museums than upon clothing, though its larvæ do attack woolen goods, feathers, hair, and silks.
[7] Anthrenus scrophulariae L.
The larvæ are not unlike other carpet beetle larvæ of the genus Anthrenus. In Figures [8] and [9] are shown the newly hatched and the mature larvæ. When unmutilated, they posses on each side at the end of the body three dense tufts of bristles and hairs. If suddenly alarmed, the larvæ erect these tufts and spread the bristles and hairs out so as to form beautiful round balls.
Fig. 8.—Varied carpet beetle: Dorsal view of newly hatched larva. Greatly enlarged.
During late spring and early summer, when the insect transforms to the adult stage in greatest numbers, the adults are driven by instinct to seek the bright sunshine and the pollen of certain flowers. In this respect they are not unlike other species of carpet beetles, the adults of which may be found also upon flowers. Some think that Viburnum or Spiraea bushes planted near the house will lure carpet beetles from the house. It is probably true, however, that the beetles, before leaving the house, lay a large percentage of their eggs, so that the attraction the sun and flowers have for them is of so little practical value to the householder that it is not worth while to depend upon flowers to lure the adults from the house.