Infraorder Cucujiformia Scientific name Bruchinae Higher classification Leaf beetle Order Beetle | Suborder Polyphaga Superfamily Chrysomeloidea Rank Subfamily | |
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Lower classifications Callosobruchus maculatus, Bruchus, Spermophagus | ||
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 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 from 1 to 22 mm for some tropical species. Colors are usually black or brown, often with mottled patterns. Although their mandibles may be elongated, 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 pupate, 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, Arecaceae, and Malvaceae, and several species are considered pests.
One characteristic of the beetles which can be seen in the photo is that the elytra are short, not quite reaching the tip of the abdomen.
Several species are native to the United Kingdom, but there are also records of several introduced species from stored products in warehouses and dwellings, although these species cannot proliferate outside of heated buildings in that climate.
