Smalleyed flour beetle
Palorus ratzeburgii (Wissmann)

Order: Coleoptera
Family: Tenebrionidae
Acronym: PRA

Ecology

The smalleyed flour beetle is found worldwide. In Canada, it is reported in Ontario and Quebec. It is a mould feeder and a scavenger and is considered to be a minor pest of stored grain. It feeds on plant and dried animal products, especially grain and cereal products. The smalleyed flour beetle feeds on damaged and mouldy grain. It is found in stored grain, milled wheat, oat products and flour mills. It is often found associated with Sitophilus species infestations. It is one of the smallest flour beetle pests and looks like a small red flour beetle, Tribolium castanteum.

Damage

The smalleyed flour beetle is a generalist feeder. The damage is not distinctive. Both the adult and larva feed on grain, flour, animal feeds, and milled products. The beetle is associated with damp grain, heated grain, mill machinery and previously infested grain. Its presence in stored grain indicates poor storage conditions. A disagreeable odour in the commodity is a sign of infestation.

Life history

The adult is a small reddish-brown beetle. It is parallel-sided and slightly flattened. It is 2.4 – 3 mm long. When viewed from the side, its eyes are entirely rounded. The adult survives for 2-3 months and it can fly.

The smalleyed flour beetle prefers to breed in milled products. Breeding conditions are temperatures between 17.5°C - 40°C and relative humidity greater than 20%. The female lays 300 eggs during her lifetime randomly in a food source. The eggs are sticky and become covered in food particles.

The larva is cylindrical and light brown. It is active and moves through the commodity. It has two very short urogomphi located at the tip of the last abdominal segment. The larva moults 6 - 8 times. The larva forms a cell to pupate in the food source. Optimal conditions for development are temperatures between 27°C and 35°C and a relative humidity between 50 and 80%. Development times ranges from 25 - 114 days depending on conditions.

Control

Controlling insect infestations

Images

Adult: Smalleyed flour beetle - Palorus ratzeburgii