Scientific Name: Cryptolestes ferrugineus (Stephens)

Common Names: Rusty grain beetle 

Synonyms

Laemophloeus ferrugineus

Taxonomic Position

Class: Insecta

Order: Coleoptera

Family: Cucujidae

Genus: Cryptolestes

Species: Cryptolestes ferrugineus

Host Range

Wheat, barley, flour, peanuts, sorghum, oilseeds, cassava root, dried fruits, chillies etc. They are also found in the nests of Vespa wasps and under tree bark. They are facultative predators and scavengers and able to feed on many species of storage fungi.

Pest Destructive Stage

Secondary pest

Both larvae and adults feed on germ and endosperm.

Identification features

Eggs

• Eggs of Cryptolestes spp. are bullet shaped.
• They average 0.53 mm long, 0.16 mm wide at their broadest diameter.
• They have one end rounded and the other end more pointed and sometimes has a nipple-like projection.
• Freshly laid eggs are glossy, non-opalescent, smooth and pellucid.

Larvae

• The newly emerged larva is about 0.7 mm long and crystal white but the head capsule and spine-like appendages of the last segment soon become reddish-brown. 
• Shape is cylindrical, tapering at each end.
• In the fully grown larva (3.6mm long and 0.6 mm at its widest), the head and thoracic segments are narrow compared with the abdominal segments.
• Each abdominal segment has 2 setae on each side.  Last instar larvae are creamy white with reddish brown head capsule and terminal segment.
• There are four larval instars, with the last moult revealing the pupae.

Adults

• The body is small and flattened shiny reddish-brown and 2 mm long with very long antennae relative to their body length. They assumes characteristic reddish brown colour after 4 - 5 days of emergence.
• A carina is present, parallel to the lateral margin, on the pronotum. There are 4 rows of setae present on the 2nd elytral interval.
• Males mandibles expanded laterally near the base and 4-segmented hind tarsi whereas females have unexpanded mandibles and 5-segmented tarsi.
• Males are usually larger than females, with slightly more filiform antennae.
•  The last three segments of the 11-jointed antennae are enlarged in both sexes. Antennae are almost as long as elytra.

Life Cycle

• Each female is capable of laying 200 to 500 eggs over a lifespan of up to nine months.
• Eggs are deposited loosely on or among the grain kernels and in the cracks or furrows on the grain surface and hatch in 3 to 5 days at 30^oC and >65% RH (ca. 13% moisture content).
• Infestations will not develop in dry grain with a moisture content of less than 12% or when the relative humidity is less than 40%. 
• After hatching, larvae feed in the germ layer of the wheat kernel and on broken kernels and grain dust.
• There are four larval instars. The fourth instar larvae produce a small amount of silk which is used to fasten together small bits of grain and other debris to make the pupation cocoon.
• Larvae infesting whole grains often form cocoons within the kernels. Before chewing their way out, newly emerged adults remain within the cocoon for a few days.
• Development from egg to adult takes 22-24 days at 32-35oC, 75% RH and ca. 15% moisture content (Mason 2003) but the development period increases at lower temperature and RH.

Detection methods

Detection of infestations by Cryptolestes furrugineus inside wheat kernels can be done by using a soft x-ray method. Cryptolestes species are easily caught in pitfall type traps inserted into commodity bulks.