The foreign grain beetle (Ahasverus advena) is a species of beetle in the family Silvanidae. It is related to the sawtoothed grain beetle.
The foreign grain beetle is approximately 2 mm (.mw-parser-output.frac{white-space:nowrap}.mw-parser-output.frac.num,.mw-parser-output.frac.den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output.frac.den{vertical-align:sub}.mw-parser-output.sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}1⁄12 in) in length. It can be distinguished from other grain beetles from its slight projections or knobs on each front corner of the pronotum, and its club-shaped antennae. However, other Ahasverus species look very similar and particular confusion can occur with Ahasverus rectus, which is also found in grain bins in North America. The larvae are worm-like, cream-colored and often reach a length of 3 mm before pupating into darker adults. Males and females are identical in appearance both as larvae and adults. The adult is usually reddish brown, or sometimes black.
The foreign grain beetle is found in tropical and temperate regions. It can complete development at temperatures between 20 and 35 °C.
At 30 °C this species can only survive if relative humidity is at least 70%, or at least 65% at 20 °C (because the equilibrium moisture content of the substrate will be similar), a condition necessary for the development of fungi on which it feeds. It feeds chiefly on fungi, including yeasts. It can often be found in grain storage facilities, where it feeds on the mold growing on the grain. It is also found on other stored foodstuff, such as peanuts and dried fruits. It can be found in various moist locations where fungus develop, such as the walls of houses around plumbing systems.
The adult female can begin laying eggs around 3 to 4 days after emerging from the pupa. It can lay up to 8 or 12 eggs per day, but generally produces 1 to 4. Eggs are laid singly or in clusters of two or three, and they hatch in 4 to 5 days. The larval stage is completed in 11 to 19 days, and pupation takes 3 to 5 days. Larval development takes longer in drier conditions. Mated males have an average life span of 159 days, and mated females live about 208 days. Unmated beetles live longer, males up to 275 days, and females up to 300.
