Foreign grain beetle (Ahasverus advena)
This beetle feeds primarily on molds and fungi growing on damp grain, grain products, and other materials. It is found throughout the world and is very common around grain processing facilities where damp, moldy grain is allowed to accumulate. Little is known about its habits in "nature", however, it is reasonable to assume this beetle can occur in any damp situation where fungi persist. When found around the home, the beetle may come from damp crawlspaces, basements, bark mulch, and possibly moldy flour or flour products. It is also very likely that the beetles originate outside and are attracted to something inside that is damp and moldy. These beetles can fly and are very small so it is possible for them find their way into the house through screens and around loosely fitting windows and doors. One odd thing about this beetle is that many of the specimens sent to this lab were collected from new homes. Possibly, because the wood, plaster, concrete and other building materials in new construction may not be completely dry, support a thin, invisible layer of fungi which attracts the beetles. Recommended control for living areas of the home includes discarding any infested food item, vacuuming, and spraying with a household insecticide (like Raid). Basements and crawlspaces can be sprayed with a persistent insecticide that is registered for indoor use. These insects will stop coming in from the outside as colder fall temperatures arrive.
Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide.
Howard Russell, Specialist
Michigan State University