Foreign Grain Beetles

While relatively small, foreign grain beetles are noticeable.

They are attracted to light and may be seen flying around light fixtures and windows.

Owners of new homes may become aware of an infestation when the foreign grain beetles begin to come out from under baseboards.

Foreign grain beetle adults are reddish-brown in color

They are about 1/8” in length.

Foreign grain beetles have a 3-segmented antennae club.

The distinguishing characteristic of the foreign grain beetle adult (when observed under magnification) is the presence of a tiny knob or bump on each of the front corners of the thorax.

Foreign grain beetles do not bite or cause any structural damage, but they may be a potential reservoir of pathogenic organisms, such as Salmonella (Spencer & Jespersen, 1998).

Besides being a nuisance, foreign grain beetles may generate liability issues in sensitive locations, such as food processing or handling places, hospitals, etc. Therefore, early detection and management of this pest is critical.

In late summer or early fall, adult foreign grain beetles fly from the fields, especially corn fields, and enter buildings seeking protected places to spend the winter.

They can enter your home through open windows and doors.

Being strong fliers, foreign grain beetles will spread to all rooms of the house.

Foreign grain beetles thrive on moldy growth on spilled grains, damp stored grain, musty cereal products, or molds on bins inside warehouses, mills, and food-handling facilities.

Foreign grain beetles have also been reported feeding on moldy pallets inside wrapped nonfood grade items.

Newly constructed homes often get wet from rain or snow during construction. As a result, mildew or mold can grow inside the home on rafters, joints, and studs. Foreign grain beetles are known to invade new homes during construction to feed on the mold, thus the nickname, “new house bugs.”

A humid bathroom can also provide a suitable environment for foreign grain beetles to thrive.

Foreign grain beetles can be attracted to older buildings in damp basements, around rotting windowsills, under moldy wallpaper, and on moist surfaces near leaky faucets.

Foreign grain beetles undergo a complete metamorphosis, in which there are four distinct stages: eggs, larvae, pupae, and adults.

The lifecycle lasts two to four weeks, depending on the temperature and relative humidity.

Female foreign grain beetles prefer to lay eggs in places with fungal growth capable of supporting larval development.

Eggs hatch in four to five days.

The larval stage lasts about 15 days and the pupa stage lasts four to seven days.

The lifespan of adults depends on the sex and mating status. Mated males and females of foreign grain beetles live an average 159 and 208 days, respectively; while unmated males and females live 275 and 301 days, respectively. (Menter & Mills, 1975)