Larval webbing can cause serious blockages and damage to processing and production machinery

Infected grains are liable to become warmer, accelerating insect problems and leading to problems with damp, mould and even grain germination

Non-compliance with legislation can lead to commodities being rejected

Contamination of foodstuffs and finished goods by insect waste materials

Common Stored Product Insect & Beetle Species

Stored product insects (common species of beetles, weevils and moths in the UK) 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 a problem or not, you can find all the signs to look out for here and find out about the feeding habits and lifecycles of stored product insects and the damage they can do if left uncontrolled.

Appearance

Approximately 3 - 4mm in length, the 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 and between 1 - 5mm in length.

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.

Appearance

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

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 are 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.

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 the 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 beetles are occasional pests of households where they feed on a wide variety of animal protein-based products. Common foods for these beetles include leather goods, hides, skins, dried fish, pet food, bacon, cheese and feathers.

The most common species are the hide and larder beetles and they are known scientifically as Dermestes maculatus and Dermestes lardarius. Both belong to the insect family called Dermestidae and are related to carpet beetles.

Life Cycle

Females require a continuous supply of water and food to achieve their maximum egg laying capacities. Female hide beetles provided with dried meat and water lay an average of 300 eggs. Eggs are laid one at a time or in small batches on the food source, and hatch within 4 to 6 days.

Control

Infestations are controlled by locating and destroying the source of the infestation and then keeping the area clean.

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

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

Feeding Habits

Dermestes beetles feed on a wide variety of animal protein based products and are serious pests in silkworm production and in museums. Common food sources include leather goods, hides, skins, dried fish, pet food, bacon, cheese and feathers. Household infestations are sometimes attributed to the presence of bird or rodent carcasses, old bird nests, or accumulations of dead insects. Dermestes may occasionally feed on plant material of high protein content, but this is not a preferred food source. Mature Dermestes larvae also bore into hard substances such as wood, cork, tobacco & plaster.

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.

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

Grain weevils live for approximately 30 days at 30°C. They 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, therefore newly emerged adults leave an identifiable emergence hole in the grain.

Appearance

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

Life Cycle

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

Feeding Habits

The Cigarette beetle is able to fly. It feeds on a wide range of stored products including tobacco, cereal, pulses, dried fruit and spices.

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 100 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, therefore newly emerged adults leave an identifiable emergence hole in the grain.

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 approximately 2.5 to 3mm in length. Their larvae are yellow to brown in colour, with a black head.

Life Cycle

Merchant grain beetles cannot tolerate low temperatures. They thrive in temperatures of 30 - 33°C.

Feeding Habits

Particularly fond of dried fruit and chocolate.

Appearance

With a flattened, light red to dark reddish brown body, the flat grain beetle is characterised by a very long antennae. Adults are an approximate 2.5mm in length, they have wings 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, with a lifespan of 60 to 100 days at 21°C and 25 days at 38°C.

Feeding Habits

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

Appearance

Male broadhorned beetles have two enlarged mandibles on the head, giving the appearance of horns hence the name. Females are very similar In appearance to the confused flour beetle.

They are approximately 3.5 to 4.5 mm in length

Life Cycle

Broadhorned flour beetles cannot complete their life cycle below 10°C. Their accepted temperature limits are 15 to 32°C.

Feeding Habits

Feeds on dough, semolina & flour etc but they may supplement their diet with moth eggs and larvae.

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

They are 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 to 14 days.

The pupal stage lasts 7 - 24 days, first white and then turning yellow (not enclosed in a cocoon) and finally emerging as adults with a lifespan of 2 to 3 months.

Feeding Habits

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

Appearance

Covered in brown and golden hairs, the Australian spider beetle has a spider-like appearance and adults grow to approximately 2.4mm to 4mm in length.

Life Cycle

Australian spider beetles live for up to 4 months at optimum temperatures of 20 to 25°C.

Feeding Habits

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

Appearance

Covered in golden-yellow hairs, the Golden spider beetle has an ovoid abdomen with a pinched waist. Adults grow to approximately 2mm to 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 to July and October to November.

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 pass through two 8-legged nymphal stages.

Life Cycle

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

Feeding Habits

Under adverse conditions, flour mites may pass through a long, resting stage called a hypopus.

Appearance

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

Life Cycle

The cheese mite favours warm, moist conditions. Eggs mature in 10 days at room temperature. Females can lay up to 900 eggs in a lifetime at a rate of 20 to 30 a day. Adults can live for up to 70 days.

Feeding Habits

They prefer old cheese to young cheese but will also feed on nuts, dried eggs, fruit, flour and tobacco. Cheese mites are capable of contaminating foods which can then cause skin or gut irritation.

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)

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.

Appearance

Grey-brown banded with lighter and darker colours, tropical warehouse moths are approximately 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.

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.

Many of these insect species are so small that you may not notice a problem at first, but always look out for the following signs of stored product insects:

• Damage to raw materials and foodstuffs.
• Emerging adult weevils leave visible exit holes in grains.
• Infected grain is liable to become warmer which can lead to damp, mould and even grain germination.
• Insect tracks through floury dust created as adults move from one food source to the next.
• Webbing produced by the larvae of Warehouse and Mill moths as they feed and spread.
• Flour and grain beetles can cause discoloration of commodities and make them prone to moulding.
• These pests can also taint goods with their waste materials.

Once in your home, stored product insects are highly mobile and will spread quickly through your property in search of other foods such as dried fruit, rice and cereals.

Act quickly as the longer you leave it the more difficult it will be to find all the sources of the infestation.

You must remove the source materials of the infestation as well as cleaning up any spillages that might occur.

Store all food products including dry pet food in strong, tightly sealed containers so that insects can't get to them.

Most stored product insects will be found in infected foodstuffs in kitchens, larders or store rooms close to a food source.

The most common insects to infest food products in homes are flour beetles, the saw toothed grain beetle and the Indian meal moth.

Flour beetles will breed in milled grain such as flour, rice, oats and cereals. They leave a mouldy taint to any products they infest.

Saw toothed grain beetles will eat cereals, dried fruits, macaroni and crackers.

Indian meal moth larvae will eat the same cereals, dried fruits and nuts as other stored product pests, but will also infest dried herbs, spices, dry dog food, fish food, cake mixes and bird seed.

Stored product insects can chew through packaging to access the food inside to eat or lay eggs.