Foreign grain beetle: A fall invading insect that prefers new homes

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

There is a strange little bug that shows up about this time every year called the foreign grain beetle, Ahasverus advena (Coleoptera: Cucujidae). This tiny beetle is considered a stored product pest in the literature, although it 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.

A Foreign grain beetles has rounded projections on the corners
of the thorax.

Foreign grain beetles have clubbed antennae.

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. One odd thing about this beetle is that most of the specimens sent to this lab are collected from new homes. Possibly because the wood, plaster, concrete and other building materials in new construction may not be completely dry and will support a thin, invisible layer of fungi which attracts the beetles. 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. These insects will stop coming in from the outside as colder fall temperatures arrive.

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