Bean weevil
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The bean weevils or seed beetles are a subfamily (Bruchinae) of beetles, now placed in the family Chrysomelidae, though they have historically been treated as a separate family. They are granivores, and 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, and several species are considered pests.
Notable species
- common bean weevil, Acantoscelides obtectus Say
- pea weevil Bruchus pisorum L.
- broadbean weevil Bruchus rufimanus Boheman
- cowpea weevil Callosobruchus maculatus
- southern cowpea weevil Callosobruchus chinensis (also known as the azuki bean beetle)
Reference
- John M. Kingsolver, "Bruchidae", in Ross H. Arnett, Jr. and Michael C. Thomas, American Beetles (CRC Press, 2002), vol. 2 (note that this reference itself indicates the group is a subfamily, and the change was made only after the chapter was written)
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