Flour Beetle - Types, Facts, and How to Identify | Flour Beetle Control |  Holder's Pest Solutions

February 26, 2021
Sawtoothed grain beetle.

The sawtoothed grain beetle, is a beetle in the superfamily Cucujoidea. It is a common, worldwide pest of grain and grain products as well as chocolate,  drugs, and tobacco. The species’s binomial name, meaning “rice-lover from  Surinam,” was coined by Carl Linnaeus, who received specimens of the beetle from Surinam.

Sawtoothed grain beetle or surinamensis is a slender, dark brown beetle  2.4–3 mm in size, with characteristic “teeth” running down the side of the prothorax. It is nearly identical to Oryzaephilus mercator, or the Merchant Grain Beetle, however, surinamensis has smaller eyes and a broader, more triangular head; surinamensis are unable to fly.


Primary pest; grain feeder
Order: Coleoptera
Family: Silvanidae
Acronym: OSU


Forewings hard and leathery, meeting along midline of dorsal surface; hindwings membranous, sometimes lacking; biting mouthparts; welldeveloped thorax; complete metamorphosis with egg, larval, pupal and adult stages. Narrow, flattened insects with 11-segmented, clubbed antennae and 5-segmented tarsi.


The beetle is one of the most commonly encountered stored product pests and is widespread within the food industry and can be found in food manufacturing, storage, and retail facilities, as well as in home pantries. O. surinamensis is less common in colder climates such as Canada and the Northern United States.

What are the signs of SAW-TOOTHED GRAIN BEETLES?

Saw-toothed grain beetles feed on products that often staples of kitchen pantry and cupboards. This includes flour, bread, breakfast cereals, macaroni, dried fruits, nuts, dried meats, sugar, dog food, and biscuits. Saw-toothed grain beetles hide in cracks and crevices and often penetrate poorly sealed packaged foods. These beetles do not fly. They are attracted to light.

Sawtoothed grain beetle

Similar species

  • Merchant grain beetle (Oryzaephilus mercator)
  • Foreign grain bettle (Ahasverus advena)

Life Cycle

A female can produce 43-285 eggs in their six to ten month average lifespan which are deposited on a food mass.

Larvae are yellow-white with brown heads and grow up to 3mm.

Larvae pupate by constructing cocoon-like coverings using broken pieces of grain. Emergence as adults occurs after about one week.

Adults can live on average six to ten months, though they can live as long as three years. The total life cycle is 27 – 51 days at 85–95 °F (29–35 °C). Adults seek out new sources of food for breeding.

flat or rusty grain beetle | Beetle, Grains, Pests

Commodities affected

  • Affects oats (beetle is most often found here), wheat, barley, animal feed, flax, sunflower
  • Affects milled and processed products, dried fruit, packaged foods
  • May attack a wide variety of foods found in homes, but this may be misidentification of O. Mercator (merchant grain beetle)

Areas where found

  • Is found in granaries, warehouses, elevators and food mills
  • Is not able to feed on sound kernels, but is able to attack even slightly damaged grain
  • Is one of the most common grain feeding insects found in grain stored on Canadian farms.

Sawtoothed grain beetle


Take the following precautions to prevent saw-toothed grain beetles:

  • Inspect food packaging for holes or rips. Do not purchase items that have been damaged or opened.
  • Store opened dry goods in sealed containers.
  • Throw out pantry items that are expired or look damaged.
  • Throw away infested food.
  • Clean your pantry with a vacuum to remove any beetles and crumbs.
  • Store food products in tightly sealed glass or plastic containers.
  • Store pet food in containers with a lid.

Importance as a Pest:
Saw-toothed grain beetles are potentially important pests of farm-stored grain. They also infest cereal products, dried fruit, dried meats, oilseeds, nuts, rice and even drugs. In grain, the mere presence of insects may result in its rejection. The germ may be damaged and when infestations become heavy they cause the grain to heat. This in turn leads to caking, moulding and even sprouting. Both the quality and weight of the grain may be reduced. Malting barley may be rejected because of poor germination, whilst milling wheat is adversely affected by tainting and discoloration. The presence of insects in other foodstuffs will render them unpalatable and cause their rejection. Merchant grain beetles mainly infest oilseeds and dried fruit whilst Foreign grain beetles attack cereal products and cocoa as well as these commodities.

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