Adult: This small beetle is predominately a secondary pest but may be a primary pest in some situations. It is reddish brown, and less than 4.5 mm long. The last five segments of the 11 segmented antennae form a club that gradually enlarges towards the tip. It is not capable of flight.
Larvae: The larva is approximately 4-5 mm long, white to yellowish in colour, and wiry in appearance. The last abdominal segment ends with two prominent points called urogomphi. Heavy infestations of flour by this insect may cause the product to turn greyish or mould prematurely. This insect can also impart a nauseous smell and taste from its scent glands to the material infested. Both adults and larvae cause damage. This beetle is an extremely important pest of flour, but also feeds on processed beans, nuts, spices, chocolate, and pharmaceuticals. Female beetles will deposit 200-500 eggs in food or on food sacks during a 1-2 year life span. Eggs hatch in 5-12 days; the larvae can mature within 22 days or can take as long as 120 days depending on the type of foodstuff and temperature. The larvae pupate in the food material and mature in 1-2 weeks. A life cycle can be completed in as few as 4 weeks under warm conditions. This species is the most common flour beetle that infests food products in Ontario.