Common Stored Product Insect Species

Stored product insects (common species of beetles, weevils and moths) not only damage foodstuff and raw materials but can also contaminate finished products – making them unfit for use.

If you’re uncertain if you have an SPI problem or not, you can find all the signs to look out for here.

Learn the feeding habits and lifecycles of stored product insects and the damage they can do if left uncontrolled.

Confused Flour Beetle

(Tribolium Confusum)

Appearance

An approximate 3 – 4mm in length, adult confused flour beetles are a red-brown in colour and typically distinguished by antennas which broaden gradually at the tip. These insects possess the ability to fly but rarely do so. Their larvae are whitish to yellow-brown in colour, 1 – 5mm long in size.

Life Cycle

Surviving approximately 20 days at 35°C and 45 days at 25°C, adults may live for up to 6 months in favourable conditions.

Feeding Habits

Confused flour beetles have a preference for clean flour, feeding on and pupating in flour and cereal products.

Rust Red Flour Beetle

(Tribolium Castaneum)

Appearance

The red rust flour beetle has close set eyes, and the last three segments of their antennae form a club. Adults grow up to approximately 3 – 4mm in length and fly in warm climates.

Life Cycle

Surviving approximately 20 days at 32.5°C and 45 days at 27.5°C, adults may live for up to 6 months in favourable conditions.

Feeding Habits

Feeds on cereals, nuts, spices and dried fruit.

Saw Toothed Grain Beetle

(Oryzaephilus Surinamensis)

Appearance

Characterised by 6 saw-like projections on each side of the thorax, the saw toothed grain beetle has a long length of head behind the eyes. Adults grow to approximately 2.5 – 3mm in length and their larvae a yellow to brown in colour, with a brown head.

Life Cycle

Surviving approximately 20 days at 35°C and 3 – 4 months at 20°C, the saw tooth grained beetle is comparatively more tolerant to temperature extremes than other pest beetles.

Feeding Habits

Feeds on cereal and cereal products, dried fruit, nuts etc.

Biscuit Beetle

(Stegobium Paniceum)

Appearance

The biscuit beetle has a humped thorax and a body covered in fine hairs, their wing cases have ridges with indentations. Adults grow to an approximate 2 – 3mm in length and larvae are known to be active in early stages of development.

Life Cycle

Surviving approximately 70 days at 28°C and 200 days at 17°C, adults may live between 13 – 65 days in favourable conditions.

Feeding Habits

Biscuit beetles possess the ability to bore into hard substances and are able to detoxify some poisonous substances. Adults do not feed.

Larder Beetle

(Dermestidae)

Appearance

Black with a whitish band across the fore-part of the wing case, larder beetles are brown in colour and hairy. Larvae are distinguished by their comet shape, and these quick moving insects are known to migrate to pupate in solid material.

Life Cycle

Larder beetles have a lifespan of approximately 2 – 3 months at 18 - 25°C.

Feeding Habits

Feeds on various animal products including cheese.

Booklice

(Psocoptera)

Appearance

The size of booklice varies according to species, typically 1 -2 mm long, they range from a pale yellow-brown to dark brown in colour. Nymphs are very small and often appear transparent.

Life Cycle

Booklice prefer high temperatures of 25 - 30°C but some species are known to breed at lower temperatures of 5 - 15°C.

Feeding Habits

Commonly found in homes and on pallets in factories.

Grain Weevil

(Sitophilus Granarius)

Appearance

With oval indentations in the thorax, grain weevils are legless and a black-brown in colour. Adults grow up to an approximate 2 – 3mm in length.

Life Cycle

Surviving approximately 30 days at 30°C, grain weevils can live for up to 8 – 16 weeks in favourable conditions.

Feeding Habits

Feeds on grain, wheat, rye, cereal. Grain weevil larvae are usually hidden where they pupate, thus newly emerged adults leave an identifiable emergence hole in the grain.

Cigarette Beetle

(Lasioderma serricorne)

Appearance

Cigarette beetles have a humped thorax, smooth wing cases and adults grow to an approximate 2 – 3mm in length.

Life Cycle

Surviving approximately 25 days at 30 - 35°C, cigarette beetles can live for 2 – 6 weeks in favourable conditions.

Feeding Habits

Possessing the ability to fly, the cigarette beetle feeds on a wide range of stored products including tobacco, cereal, pulses, dried fruit and spices.

Rice Weevil

(Sitophilus Oryzae)

Appearance

With round indentations on the thorax and reddish spots on their wing cases, the legless rice weevil can grow up to an approximate 2 – 3mm in length.

Life Cycle

Surviving approximately 98 days at 18°C, rice weevils can live for several months to a year in favourable conditions. Larvae will not develop below 16°C.

Feeding Habits

Feeds on grain and seeds. Rice weevil larvae are usually hidden where they pupate, thus newly emerged adults leave an identifiable emergence hole in the grain.

Merchant Grain Beetle

(Oryzaephilus Mercator)

Appearance

With 6 saw-like projections on each side of the thorax and a short length of head behind the eyes, merchant grain beetles grow up to an approximately 2.5 – 3mm in length, their larvae a yellow to brown in colour, with a black head.

Life Cycle

Merchant grain beetles cannot tolerate low temperatures and thrive in optimum conditions of 30 – 33°C.

Feeding Habits

A particular pest of dried fruit and chocolate.

Flat Grain Beetle

(Cryptolestes Pusillus)

Appearance

With a flattened, light red to dark reddish brown body, the flat grain beetle is characterised by a very long antennae and adults are an approximate 2.5mm in length. Adults are winged but rarely fly. Larvae are a yellow-white in colour, developing from 0.5mm to 4mm when mature.

Life Cycle

The flat grain beetle prefers warm, damp conditions, surviving 69 – 103 days at 21°C and 26 days at 38°C.

Feeding Habits

Feeds on cereal, dates, dried fruit and other produce.

Broadhorned Flour Beetle

(Gnatocerus Cornutus)

Appearance

An approximate 3.5 – 4.5mm in length, male broadhorned beetles have two enlarged mandibles on the head, giving the appearance of horns and thus their name. Females are very similar In appearance to the confused flour beetle.

Life Cycle

With temperature limits of 15 - 32°C, broadhorned flour beetles cannot complete their life cycle below 10°C.

Feeding Habits

Feeds on flour, dough, semolina etc. Moth eggs and larvae may supplement the broadhorned flour beetle diet.

Yellow Mealworm Beetle

(Tenebrio molitor)

Appearance

Approximately 20mm long, yellow mealworm beetles are shiny, dark-brown or black. Larvae are a honey-yellow color with hard, highly polished worm-like body.

Life Cycle

Highly resistant to cold temperatures, females lay about 275 – 600 white, bean-shaped eggs singly or in clusters during spring, which hatch into larvae in 4 – 14 days. The pupal stage lasts 7 – 24 days – first white, turning yellow (not enclosed in a cocoon) and finally emerging as adults with a lifespan of 2 – 3 months.

Feeding habits

Adult yellow mealworm beetles are attracted to night-lights, and the strong fliers are commonly found in dark areas.

Australian Spider Beetle

(Ptinus Tectus)

Appearance

Covered in brown and golden hairs, the Australian spider beetle has a spider-life appearance and adults grow to an approximate 2.4 – 4mm in length.

Life Cycle

Australian spider beetles live for up to 3 – 4 months at 20 - 25°C.

Feeding Habits

Larvae are often found feeding on miscellaneous debris, and the Australia spider beetle possesses the ability to bore into various inedible materials prior to pupation. Active in dark, damp places, the Australian spider beetle is often associated with bird nests.

Golden Spider Beetle

(Niptus Hololeucus)

Appearance

Covered in golden-yellow hairs, the Golden spider beetle has an ovoid abdomen with a pinched waist and adults grow to approximately 2 – 4.5mm in length.

Life Cycle

Surviving up 6 – 7 months at 20°C, the Golden spider beetle can live up to 9 months in favourable conditions.

Feeding Habits

Commonly linked to the damage of textiles in the domestic home, adults appear in greater numbers from June – July and October – November.

Flour Mites

(Acarus Siro)

Appearance

White or pale brown in colour, the slow moving flour mite can grow up to 0.5mm long. Larvae are white in colour and passes through two 8-legged nymphal stages.

Life Cycle

Flour mites have a lifespan of 9 – 11 days at 23°C and 90% relative humidity.

Feeding Habits

Under adverse conditions, flour mites may pass through a long and very resistant stage called a hypopus.

Cheese Mites

Appearance

Cheese mites have soft, hairy cream white bodies with 8 hairless legs and adults grow up to an approximate 0.5mm in length.

Life Cycle

The cheese mite favours warm, moist conditions and eggs mature in 10 days at room temperatures. Females can lay up to 900 eggs in a lifetime at a rate of 20 – 30 a day. Adult cheese mites can live for up to 60 – 70 days.

Feeding habits

With a preference for old cheese to young cheese, these mites also feed on nuts, dried eggs, fruit, flour and tobacco. Cheese mites are capable of contaminating foods to cause skin or gut irritation.

Indian Meal Moth

(Plodia Interpunctella)

Appearance

An approximate 7 – 9mm in length, the wingspan of an Indian meal moth develops to 15 – 20mm; the first third of forewings are a pale buff colour and the remainder of the winds are a reddish-brown. Larvae are a yellowish-white, reddish or greenish (depending on diet) with a brown head.

Life Cycle

Surviving for 35 days at 35°C, the Indian meal moth lives for much longer at lower temperatures or when feeding on low nutrition foods.

Feeding habits

Feeds on nuts, dried fruit and grain (maize)

Mill Moth

(Ephestia Kuehniella)

Appearance

Characterised by a black zig zag pattern across grey wings, the mill moth is an approximate 7 – 9mm in length with a wing span of 15 – 20mm. Larvae lives within a silken tube and have a pinkish or greenish tinge (depending on diet) with a brown head.

Life Cycle

Surviving for 153 days at 17 and 42 days at 30°C, the prolific silk spinners can live for up to 2 weeks in favourable conditions.

Feeding Habits

A pest particular to flour, rarely feeds on other products.

Tropical Warehouse Moth

(Ephestia Cautella)

Appearance

Grey-brown banded with lighter and dark colours, tropical warehouse moths are an approximate 7 – 9mm in length with a wingspan of 15 – 20mm. Larvae are whitish, yellowish or reddish in colour (depending on diet) and tend to migrate to dark areas to pupate.

Life Cycle

Tropical warehouse moths have a lifespan of 31 days at an optimum temperature of 32°C.

Feeding habits

Often associated with imported food cargoes, the tropical warehouse moth is primarily a pest of stored cereal, nuts, dried fruit, oil seeds and oil cakes. Rarely feeds on tobacco and animal products. Adults do not feed.

Warehouse Moth

(Ephestia Elutella)

Appearance

An approximate 7 – 9mm in length with a wing span of 10 – 16mm, the warehouse moth is grey-brown banded with lighter and darker colours. Larvae are whitish, yellowish or reddish in colour (depending on diet) and tend to migrate to dark areas to pupate.

Life Cycle

Eggs hatch from 3 -6 days above 20°C and pupae matures from 10 – 20 days over a temperature range of 18 - 26°C.

Feeding Habits

A formidable pest of cocoa beans, chocolate confectionary, dried fruit and nuts.