Pill Beetles
Additional images: ventral view (click here).
Identification:
5mm-10.0mm long. Form highly convex and oval. These are generally small to moderately sized beetles. Members of the Family Byrrhidae are hard-bodied, convex, and black. The body is covered with tiny hairs or scales. Nearly 100 species are recorded in the United States and Canada (Comstock, 1920).
The head is bent downward and concealed from above. The antennae are stout, clavate, short and rarely extending beyond the base of the pronotum. The antennae are not clubbed. The palps are long and flexible. Prosternal sutures are nearly always present.
The prothorax is without notopleural sutures.
The wide hind coxae extend to the elytra, and are grooved for the compact retraction of the femora. At least one tarsal segment is with lobes. The tarsal formula is 5-5-5. The hind trochanters are small. The hind coxae are not so expanded.
The elytra covers all or nearly all of the abdominal segments. The first abdominal sternum is not divided by the hind coxae. The abdomen with 5 or 6 visible abdominal sterna. All abdominal sterna are separated by equally distinct sutures. Metasternum usually without transverse suture.
Natural History:
Defensive behavior consists of retracting legs, (the femora fitting into the coxal cavities) and antennae, forming a compact "pill" when disturbed, remaining motionless (Borror, et al. 1989).
Members of this family are found in sandy localities such as shore lines, among grass roots, and beneath debris such as logs and stones (Bland, 1978).
Adults and larvae are phytophagous, feeding mostly on moss in the both the adult and larval stage (Gillot, 1980).
Literature Cited:
Bland, R. G. 1978. How to Know the Insects, 3rd Edition. Dubuque, Iowa, Wm. C. Brown Company Publishers.
Borror, D. J., Triplehorn, C. A., and Johnson, N. F. 1989. An Introduction to the Study of Insects, 6th Edition. New York, Saunders College Publishing.
Comstock, J. H. 1920. An Introduction to Entomology. Binghamton, New York, Vail-Ballou Press. Gillot, C. 1980. Entomology. New York, Plenum Press.
