Bean weevil

about 1,350 species

The bean weevils or seed beetles are a family Bruchidae (Latreille 1802) of beetles. They typically infest various kinds of seeds or beans, living for most of their lives inside a single seed. The family includes about 1,350 species found worldwide.

Bean weevils are generally compact and oval in shape, with small heads somewhat bent under. Sizes range to 1 mm, up to 22 mm for some tropical species. Colors are usually black or brown, often with mottled patterns. Although their mandibles may be elongate, they do not have the long snouts characteristic of true weevils.

Adults deposit eggs on seeds, then the larvae chew their way into the seed. When ready to pupaate, the larvae typically cut an exit hole, then return to their feeding chamber. Adult weevils have a habit of feigning death and dropping from a plant when disturbed.

Host plants tend to be legumes, but species will also be found in Convolvulaceae, Palmaceae , and Malvaceae.

Some authorities place the bruchids in Chrysomelidae.

Notable species

• common bean weevil , Acantoscelides obtectus Say
• pea weevil Bruchus pisorum L.
• broadbean weevil Bruchus rufimanus Boheman
• cowpea weevil Callosobruchus maculatus

Reference

• John M. Kingsolver , "Bruchidae", in Ross H. Arnett, Jr. and Michael C. Thomas, American Beetles (CRC Press, 2002), vol. 2