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Stored Product Insects

There are a wide variety of Stored Product Insects which can become a problem both for domestic and commercial customers.

Please find below some of the more common varieties:

Red Flour Beetle/Confused Flour Beetle 
 (Tribolium castaneum/Tribolium confusum)


Found throughout the world on a variety of products the Red Flour Beetle is more common in warmer climates than the Confused Flour Beetle.

Minimum Life Cycle: 20 days.


Red Flour Beetle (Tribolium casteneum)
Eggs: approximately 450 per female over several months, laid on food stuffs.

Larvae: these prefer cereal embryos.

Adults: 3.5mm in length, can live for 18 months, some strains can be resistant to some insecticides.

(Images: Top-Red Flour Beetle, Bottom-Confused Flour Beetle)

Grain Weevil (Sitophilus granarius)


Temperate zones, attacks cereal grains.

Minimum Lifecycle: 4 weeks


Eggs: up to 200 per female laid within grains

Larvae: live within the grains, can survive for 10 weeks at 5c.

Adults: 3.5mm in length, cannot fly, can easily survive UK winter in unheated buildings.

Rice Weevil (Sitophilus oryzae)


Both tropical and temerate zones, found on cereal grains.

Minimum Lifecycle: 4 weeks


Eggs: up to 200 per female in stored cereal grains and by flying adults in grains in the field. 

Larvae: feed on the grain.

Adults: 2.5mm in length, also feed on the grain, cannot normally survive a winter in temperate climate without heat.

Tobacco Beetle (Lasioderma serricorne)


Worldwide, primarily found on tobacco but can be on other products.

Minimum Lifecycle: 19 days


Eggs: approximately 100 per female laid on produce.

Larvae: these are responsible for the damage as they feed on the product. Developemtn time is dependent on food availability.

Pupae:  these form within the produce.

Adults:  3mm in length, do not feed, they can live for 2 - 4 weeks.

Lesser Grain Borer (Rhizoperha dominica)


Throughout the world, both in cereal and coarse grains.

Minimum Lifecycle: 25 days.


Eggs: up to 500 per female.

Larvae: voracious feeders, eat into grains and also feed on grain dust.

Pupae: these usually form within the grain.

Adults: 3mm long, also are voracious feeders and are long lived.

Larger Grain Borer (Prostephanus truncatus)


Americas and now Africa, maize growing areas.

Minimum Lifecycle: 25 days.


Eggs: up to 600 per female laid among grain.

Larvae: feed on maize.

Adults: 4mm in length, can fly, will also attack other foodstuffs.

Rust Red Grain Beetle (Cryptolestes ferrugineus)


Worldwide, normally secondary pests but will also attack damaged grains.

Minimum Lifecycle: 23 days.


Eggs: laid in produce, often in splits or cracks in grain.

Larvae: feed on or near the endosperm of the grain.

Adults: 2mm ling, also feed and can live 6 - 9 months.

Saw-toothed Grain Beetle (Oryzaephilus surinamensis)


Worldwide, important pest of many stored products and a secondary pest of whole grain.

Minimum Lifecycle: 20 - 25 days.


Eggs: up to 400 per female laid in the grain.

Larvae: develop  quickly, particularly where there is high moisture content.

Adults: 3.5mm long, can be long-lived up to about 3 years.

Merchant Grain Beetle (Oryzaephilus mercator)


Worldwide, as above an important pest species of stored products.

Minimum Lifecycle: 20 - 25 days.


Eggs: up to 400 per female.

Larvae: as above, develop rapidly at high humidity.

Adults: 3.5mm in length, can live for up to 3 years.

Khapra Beetle (Trogoderma granarium)


The most important stored product pest for grain importers and exporters, these primarily attack grain and oil seeds.

Minimum Lifecycle: 25 days to 4 years in diapause (lying dormant).


Eggs: up to 80 per female.

Larvae: may enter diapause under unfavourable conditions when it becomes difficult to treat.

Pupae: in crack and crevices.

Adults: 3mm long, short-lived do not feed or fly.

Dried Bean Beetle (Acanthoscelides obtectus


Worldwide on pulses both before harvest in the field and when stored.

Minimum Lifecycle: 3-4 months.


Eggs: laid in pods before harvest and among stored seeds.

Larvae: enter and feed within one seed.

Pupae: form within the seed.

Adults:  3.5mm in length, non-feeding and short lived. 

Flour, Grain or Cheese Mites (Acarus siro)


Throughout the world, will attack many types of produce especially if moisture content high or have been attacked by fungus.

Minimum Lifecycle: 17 days.


Eggs: minimum 100 per female, egg stage can survive at 0 degrees for months.

Immature Stages & Adults: attack cereal embryos, dormant stage resists starvation, chemical treatments and dessiccartion.

Mill Moth (Ephestia kuhniella)


Temperate areas, attacks cereal products especially flour.

Minimum Lifecycle: 6 - 9 months


Eggs: laid on or near to produce.

Larvae: like flour dust, webbing from heavy infestations can clog machinery.

Pupae: form in the produce from overwintered larvae.

Adults: 21mm long, do not feed and are short lived.

Warehouse, Cocoa or Tobacco Moth (Ephestia elutella)


Temperate areas, a serious pest which attacks many raw and processed products.

Minimum Lifecycle: 6 -9 months.


Eggs: laid near or on produce.

Larvae: move to and over produce feeding and spinning threads which can form webs.

Pupae: form in cracks.

Adults: 16mm in length, do not feed, short-lived and fly at dawn and dusk.

Tropical Warehouse Moth (Ephestia cautella)


Tropical areas, attacks a wide variety of products.

Minimum Lifecycle: 25 days.


Eggs: up to 300 per female on or near produce.

Larvae: move to and over produce spinning threads, particularly thickly prior to pupating.

Pupae: these form near to produce.

Adults: about 16mm long, these are non-feeding and short lived. they tend to fly around dusk and dawn.

Indian Meal Moth (Plodia interpunctella)


Worldwide in cereals, ground nuts and dried fruit.

Minimum Lifecycle: 26 days


Eggs: laid near produce up to about 300 per female.

Larvae: spin threads as they feed, when in the pre-pupal diapause they can be difficult to treat with insecticide.

Pupae: these form in produce.

Adults: approximately 16 mm in length, short lived and do not feed.

Angoumois Grain Moth (Sitotroga cerealella)


In tropical grains, for example maize, and sorghum. They commonly attack prior to harvest.

Minimum Lifecycle: 4 weeks


Eggs: these are laid on the surface of the grain.

Larvae: they bore into the grain and remain there until pupation.

Pupae: these also form within the grain.

Adults: about 16mm long, these do not feed and are short lived.