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Sawtoothed grain beetle

Most recently reviewed by: Janet Hurley & Pat Porter (2018)

Common Name(s): Sawtoothed Grain Beetle

Pest Location

Urban Structural


The adult beetle is a small (1/10 inch long), very flattened and brown with the segment just behind the head (pronotum) having characteristic “sawtoothed” outer margins, bearing six “teeth” on each side.

A closely related species, the merchant grain beetle, Oryzaephilus mercator (Fauvel), is very similar to the sawtoothed grain beetle but differs in the dimensions of the head capsule (i.e., the temple region just behind the eyes is shorter, less than the vertical diameter of the eye for the merchant grain beetle, being longer for the sawtoothed grain beetle).

Mouthparts are for chewing. Adults find their way into stored grains, flour, sugar, nuts and other dry material of plant origin through cracks and crevices of imperfectly sealed containers. They are incapable of attacking sound grain kernels and often occur in food previously infested by other stored product pests. This pest may be found infesting dry goods, crawling around kitchen surfaces and occasionally underneath tree bark.

Beetles can infest stored dry goods in the pantry; adults leave infested food sources can occur in the kitchen or other food storage areas and be a nuisance; medically harmless.

Origin and Distribution

This is a common, worldwide pest of grain and grain products as well as fruit, chocolate, drugs, and tobacco.

Habitat & Hosts

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.  Prefers damaged or processed grain to establish in significant numbers. Adults can live for seveal months, females laying 300 to 400 eggs losely throughout the grain.  White larvae feed and develop externally.

Life Cycle

Fertilized females lay numerous shiny white eggs, singly or in clusters, in foodstuff and packaging. Larvae hatch from eggs in 3 to 17 days depending on temperature. Yellowish-white, deeply segmented larvae develop through several (two to four) stages (instars) while growing to about 1/8 inch long. Pupation often occurs in cells made of food particles cemented together, usually onto a solid object. Development from egg to egg occurs in 27 to 375 days. Four to six generations can occur annually.


If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Prevention is the best strategy to avoid insect problems in stored grains. Proper bin sanitation before introduction of new grain minimizes the need for pesticides. Good sanitation involves the removal of old grain and dust in and around the gain bin. This includes removal of old grain from corners, floors, and walls. Any grain remaining when a bin is emptied can harbor insect infestations which will move into the new grain. Grain that is to be stored for longer than six months may need a protective application of an approved insecticide.

Grain placed in a clean bin should be checked at two week intervals during warm months and at one month intervals during cooler months for the presence of hotspots, moldy areas, and live insects. If any of these conditions exist, the grain should be aerated to lower the moisture level and temperature.  Sieving and probe traps are recommended for detection.

Fumigation should only be used as a last resort. Because of the high toxicity of registered fumigants and technical knowledge needed for their proper use, a qualified pesticide applicator should be contacted if fumigation is required.

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