Scientific Name: Oryzaephilus surinamensis (Linnaeus, 1758)

Common Names: Saw-toothed grain beetle

Synonyms

Colydium frumentarium, Dermestes sexdentatus,  Dermestes surinamensis, Silvanus bicornis, Silvanus surinamensis 

Taxonomic Position

Phylum: Arthropoda

Class: Hexapoda (Insecta)

Order: Coleoptera

Family: Silvanidae

Host Range

It prefers cereals, cereal-based products, but also copra, spices, nuts, dried fruit etc.

Pest Destructive Stage

Secondary Pest

Both adult and larva can cause the damage.

Damage Symptoms

Larvae and adults are general feeders and damage caused is not readily identifiable as being specifically caused by these insects. Larvae and adults will attack on previously damaged or broken kernels to feed, especially on the germ. Adults and larvae are able to enter in small cracks, so they can often attack packaged food or nuts in shell. On copra, the larvae tend to feed close beneath the outer skin.

Identification Features

Eggs

• Its eggs are white to yellow-ochre, capsule -shaped and about 0.7 mm long.

Larvae

• The larva is elongate yellowish-white with a brown head, has numerous setae (hairs) and three pairs of legs.

Adult

• The saw-toothed grain beetle is a slender dark brown beetle 2.4-3 mm in length, with a flattened bod.
• Six saw-toothed projections (“teeth”) on each side of the prothorax.
• The abdomen tapers towards the tip and it rarely flies.
• Its antennae are long and moniliform (“bead-like").

 Similar Species

Oryzaephilus mercator (Fauvel), the merchant grain beetle, is nearly indistinguishable from the saw-toothed grain beetle, O. surinamensis in appearance. Small differences in the shape of the head and in their genitalia are used to differentiate them. The saw-toothed grain beetle is more commonly found on cereals while the merchant grain beetle prefers oil-seed products.

Life Cycle

• The female saw-toothed grain beetle lays eggs singly or in small batches in the food product.
• Female lays about approximately 400 eggs in her lifetime. The eggs hatch in 3-8 days. Larvae are free-living and usually pass through four instars. They are unable to feed on undamaged grains.
• The life cycle takes from 20-80 days dependent on temperature and the adults usually live around 6 to 10 months.
• Adults normally disperse by walking but can fly at dawn and dusk in warm conditions. Long distance dispersal takes place in contaminated foodstuffs.

Detection methods

The saw-toothed grain beetle can be detected by visual inspection. Saw toothed grain beetles are very active mobile insects that are easily captured in pitfall type traps inserted into grain.