Scientific Name: Cryptolestes pusillus Schönherr

Common Names: Flat grain beetle

Synonyms

Laemophloeus minutus, Laemophloeus pusillus

Taxonomic Position

Class: Insecta

Order: Coleoptera

Family: Laemophloeidae (Cucujidae)

Genus: Cryptolestes

Species: Cryptolestes pusillus

Host Range

• 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 and sunflower seeds etc.

Pest Destructive Stage

Secondary Pest

Larvae and adults both can feed on commodity.

Damage Symptoms

C. pusillus feeds on damaged grains, dried fruits, nuts and other stored plant materials. Damage caused by this pest cannot be distinguished from that caused by many other stored-product insects, except by identification of the insects present.

The larvae and adults feed on damaged grains and will burrow into the grain to feed. On softer stored plant materials, C. pusillus will feed on undamaged material. C. pusillus infestations may increase the temperature and moisture content of stored commodities, thus increased levels of microorganisms may accompany infestations.

Identification features

Eggs

The eggs are translucent white, elongate and ovoid. The eggs are about 0.25 mm in diameter and 0.75 mm in length.

Larvae

• There are four larval instars (occasionally there is a supernumerary moult) and a quiescent pre-pupal stage.
• The head is wider than the rest of the body in the first instar, but then becomes narrower in later instars.
• After the first instar, there is a pair of lateral setae on abdominal segments 1-7. The mature fourth stage larva is 3-4 mm in length.

Pupae

The pupal stage occurs in a silken cocoon. The newly-formed pupa is white, but becomes darker with age. The pupal cocoon is slightly longer than the mature larva.

Adults

• Adults are small (1.5 to 2.0 mm), reddish brown and flattened with long bead-like (filiform) antennae.
• Adults have a ridge (sublateral carina) on the head and prothorax.

Detection methods 

Visual examination of stored commodities may reveal an infestation. However, the insects prefer to feed within the commodity and an internal examination of the commodity is, therefore, required for positive determination of infestation. The methods used for internal examination depend can be either slicing open a grain with a razor blade or X-rays.

Probe traps may be used to sample any mobile stage of the insect in stored grain. However, these traps are only effective when temperatures are warm enough for movement, and correlating trap catch with actual insect population levels is difficult.

Absolute numbers of insects may be determined by taking samples of grain using grain triers, but this method requires separation of the insects from the grain. Food baits or food extracts may be used to increase the efficiency of probe traps. Bait packets and sticky traps have been used to sample C. pusillus outside commodity storage facilities.