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Grain Beetles

General Facts

Several species of grain beetles live in Canada and cause problems in homes and businesses alike. The pantry pests attack stored grains, cereals, flour, spices, and other processed food products. Some of the most common species in Canada include the sawtoothed grain beetle, the merchant grain beetle, the lesser grain beetle, the rusty grain beetle, and the foreign grain beetle. Each species of these destructive pests enjoys a pervasive and consistent presence throughout the country.

Appearance / Identification

an image of two flat grain beetle
Most grain beetles measure between 2 and 3 mm in length and appear either brown or dark red in colour. Typically, the insects look slightly flattened in appearance. Some of the more common grain beetle species in Canada are clearly identifiable from the six projections on the thorax that look similar to saw blades. Certain types of grain beetles also possess large and prominent eyes, which make the shape of the head noticeably pointier in comparison to other species.

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Found throughout Canada, grain beetles are commonly encountered in a variety of manmade structures, such as grain elevators, warehouses, mills, home pantries, and railroad cars and cargo ships which transport food items. With their flattened bodies, most adult grain beetles can easily penetrate and hide in cracks and crevices. Some species are more tolerant of colder temperatures, which allows certain types of grain beetles to live farther north than other beetle species.


Grain beetles, as the name suggests, primarily feed on grains. While different types of grain beetles may favour certain grains and stored foods, the list of preferred grains is largely similar across species. For instance, the sawtoothed grain beetle primarily feeds on oats, wheat, barley, and animal feed, along with an array of processed and packaged foods found in the home. Other species, such as the merchant grain beetle, prefer foods with higher oil content, such as oatmeal, bran, and brown rice, in addition to processed cereals, seeds, and dried fruit.

Life Cycle / Reproduction

The life cycle of the grain beetles consists of the egg, larval, pupal, and adult stages. All species of grain beetles lay eggs individually or in batches deposited in or around a ready food supply. The eggs are difficult to see with the naked eye. Depending on the species, a female grain beetle may lay between 40 and 300 eggs each year. Larvae typically emerge in 3 to 10 days, depending on heat and humidity, and reach full adulthood within two months. Adult grain beetles may only live for 6 to 10 months, though the insects have been known to live up to three years in ideal conditions.

Problems Caused by Grain Beetles

Grain beetles feed on nearly any stored food product, particularly cereals, breakfast foods, flour, dried fruits and meats, pet foods, and many other items. While the insects are not known to carry or pass any diseases to humans or pets, they make pantry products unfit for consumption. Additionally, when the pests are found in purchased grains, they typically alarm people by their presence and may indicate the existence of an infestation problem where the product was manufactured or bought. Grain beetle infestations can cause granaries, warehouses, mills, and even retail establishments to lose business and profits over time.

Detection / Signs of Infestation

As grain beetle eggs and larvae are small and difficult to spot, visible signs of infestation may be difficult to detect. Nevertheless, one way to recognize the presence of grain beetles is to check the temperature of the potentially infested product. When an infestation proves severe enough, the affected grain tends to overheat. The sight of adult grain beetles crawling on surfaces near stored products also indicates a possible infestation. In improperly sealed and stored foods, visible entry and exit holes may become visible.

Prevention Tips

The easiest way to prevent grain beetle infestations is to keep food storage areas clean and properly sanitized. Purchase dried foods, grains, cereals, and spices in small quantities that will be used in a relatively short period of time. Rotate stock by using older products before opening new packages. When possible, store all foods in refrigerators or freezers in tightly closed containers made of glass, metal, or heavy plastic. Thoroughly clean the crevices and corners of food storage areas, utilizing a vacuum cleaner where possible, and wipe up food spills promptly.

Control / Removal

Discard infested food items, though exposing the infestation to extreme heat or extreme cold may also be effective before the problem becomes too severe. The use of store-bought traps, in addition to continued vacuuming and other sanitation steps, may work for smaller infestations. Insecticide products, however, should not be used around food products, but spraying in cracks and crevices where the insects live may help eliminate the pests. For extreme infestations, it may become necessary to contact a trained pest control specialist in order to completely eradicate the invading insects.

Get Rid of Sawtoothed Grain Beetles
Merchant Grain Beetles
Pictures of Grain Beetles