Flat grain beetle

Cryptolestes pusillus (Schönherr)


Primary pest; grain feeder
Order: Coleoptera
Family: Laemophloeidae
Acronym: CPU


  • Adults are small (1.5 to 2.0 mm), reddish brown and flattened with long bead-like antennae.
  • Adults have a ridge (sublateral carina) on the head and prothorax.
  • Larvae are elongate and flattened with well-developed legs.
  • Larvae are pale, white to yellow in colour with a darkened head capsule and dark urogomphi present.
  • Male antennae are longer (almost as long as body) than female antennae (half the length of the body); rusty grain beetle antennae are the same length in both sexes.


Similar species

Commodities affected

  • Mainly damages grain, preferably wheat
  • Will also feed on beans, bulbs, cacao, cereal products, citrus pulp, copra, cottonseed, cowpeas, maize, malt barley, filberts, nutmeg, rice, sorghum, soybeans, sunflower

Signs of infestation

  • Damage is not readily identifiable as being caused by this species.


  • Damage is usually restricted to grain stored under high moisture conditions.
  • Both larvae and adults feed on germ and endosperm.
  • Heavy infestations may cause grain to heat and spoil.
  • Damage may spread fungal spores through grain.

How to control

Geographic range

  • Is distributed worldwide, but is more common in wet-tropical and warm-temperate regions
  • Is found in Canada from Quebec west to British Columbia

Where found

  • Is found mainly in grain elevators and flour mills, warehouses, farm-stored grain
  • Is often confused with the flour mill beetle (Cryptolestes turcicus)
  • Is probably the least damaging species of Cryptolestes in Canada
  • Can survive Canadian winters only in heated structures

Life history

  • Females lay eggs in crevices or loosely amongst the food.
  • Larvae move actively amongst the food feeding on the endosperm or germ Adults cannot climb up glass.

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