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Beetles
Life Cycle & Description
Description of
Australian Spider Beetle
(Ptinus tectus)
Habitat
One of the family called spider beetles. This species originally Tasmanian origin but established in the UK in 1800s. Indoor warehouse and food storage scavenger, often in birds’ nests. Prefer food of high animal protein content.
Biology
Egg – larva – pupa – adult.
Eggs – whitish, up to 200 per female, 6–50 per week on or near larval food. Larvae – whitish, active when first hatched, can penetrate packaging, sacks to enter foodstuffs. Become grub-like and immobile when larger.
Pupae – in cocoons often in clusters or lines near foodstuff.
Adults – 3–4mm, mid- brown, superficially spider-like appearance. Cluster in groups during the day on sacks and between floor boards. Wander at night to feed . Cannot fly.
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Importance
Food storage pest attacking cereal products, dried fruit, pulses, spices, dog biscuits. Larvae damage packaging.
Control
Find breeding sites, remove old birds nests, proofing, good hygiene, stock rotation. Residual sprays or dusts
Distribution and Habitat
Although originally of Tasmanian origin, this species spread to the UK in the 19th century and subsequently (over a 20-30 year period) throughout Britain. It lives almost always indoors, is frequently associated with dry birds' nests occurring in buildings, and favours a diet with a high animal protein content.
Biology
The eggs are laid loosely amongst the larval food material. The young larvae can chew through paper, cardboard and sack fibres to gain access to the food. They tend to remain static inside the foodstuff developing as fleshy, curved "grubs" until forming a silken cocoon (often against adjacent hard or solid surfaces). The adults emerge from the cocoons that may have been formed in clusters or lines. The adults do not fly.
The females lay over 200 eggs on average and these take seven to ten days to hatch. The larvae develop over 40–50 days, according to food and temperature. Adults’ emergence from the pupae occurs 20–25 days later. The adults are very cold-hardy being active down to 2 °C.
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Around 25 °C is about ideal but a supply of drinking water is essential. Normally two generations per year occur in unheated premises and the adults can live up to 12 months.
Preferred foods include grain, flour, spices, dried fruit and nuts, and miscellaneous spillages and debris in stores and warehouses. They will scavenge on dead insect remains, and enjoy the conditions in dry birds' nests. The adults wander considerable distances at night (maybe in search of water) and may "infest" many stored but otherwise inedible materials. They also tend to be gregarious, and may be found clustered behind sacks, beneath scraps of cardboard and timber, and in the cracks between skirting-boards. They hide in the day and are active in darkness.
Importance
The Australian spider beetle is widespread and common in the food industry – primarily in storage situations. It infests many foodstuffs and can cause significant physical damage, hollowing-out spices, dried pulses and dog biscuits. The wandering adults will contaminate a wide range of food and non-food materials. The larvae, during pupation especially, will bore through many packaging materials causing costly damage and sometimes significant spillage.
The species also occurs domestically (again usually associated with nests in lofts / eaves) and can seriously damage clothing and fabrics in homes.
Control
The source of infestation should be traced and any infested commodities destroyed. Old birds' nests should be removed and destroyed. Residual spraying or dusting of the structure will generally achieve effective control, subsequent to improvements in hygiene (especially removal of old residues), remedying structural defects and ensuring good stock rotation.
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Other Species
White-Marked Spider Beetle (Ptinus fur)
This species occurs in similar situations to P. tectus , but is less common and usually in smaller numbers. The males and females differ in size, shape (males more slender body) and colour (females usually more darkly coloured) with four very distinct white flecks on the elytra (wing cases). Recent experiences suggest that this species may occur in surprisingly large numbers in long-term grain stores, as a wandering population, probably scavenging on dead insect and mite bodies. It is less commonly encountered domestically, and is more a food storage pest.
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Golden Spider Beetle (Niptus hololeucus)
An apt common name, this much larger (3–4.5mm compared with 2.5–3.5mm for P. tectus) spider beetle has a roughly spherical shape and is clothed most attractively in golden hairs and scales. It is an obvious insect and occurs quite commonly in flour and feed mills, food warehousing and the domestic environment. Seldom seen in more than small numbers, it is usually only a contaminant pest, although as with the preceding spider beetles, the larval habit of chewing and boring can damage packaging materials. It prefers a vegetable-based diet and the adults require drinking water.
Description of
Biscuit Beetle
(Stegobium)
Habitat
Worldwide but more common in temperate regions. Pest of food stores and domestic larders. Feeds on cereal products, spices and wide range of dried stored foodstuffs. Can penetrate food packaging.
Biology
Egg – larva – pupa – adult.
Eggs – up to 60 per female laid singly on or near larval food. Hatch 1–2 weeks .
Larvae – whitish, mobile when first hatched, may penetrate packaging material. Become sluggish when larger. May bore holes through hard food materials. Develop 2–4 months.
Pupae – inside cocoons in or near larval food. Develop 1–2 weeks.
Adults – 2–3 mm, brown, partially humped thorax, distinctive 3 segmented antennal club.
Can fly.
Live 3-4 weeks.
Importance
Food storage pest often causing localised heavy infestations in old stock. Possible confusion with furniture beetle (woodworm).
Control
Destroy infested materials. Professional fumigation of bulk foods. Good hygiene. Residual insecticides for structural treatments.
Distribution and Habitat
The biscuit beetle is found worldwide but more commonly in temperate latitudes. It is common throughout the UK, especially in food storage and retailing premises, and frequently encountered as a domestic pantry pest.
Biology
The eggs are laid freely amongst the larval foodstuff and the newly hatched larvae crawl or chew their way through most packaging materials to feed voraciously.
Preferred foods include spices and cereal products, including biscuits, but it will attack many other hard ''foods" including rodent bait pellets, insect collections, and manufactured high protein dog chews. Powdered packeted soups and drinks may also be damaged.
The larvae require a minimum of around 10% relative humidity, up to a maximum of 70% after which mould usually develops in the food medium and kills the larvae.
After two months or so, depending on temperature, the larvae pupate inside cocoons, often within the food material, and one or two weeks later the adults hatch, their emergence holes resembling typical "woodworm" (Anobi um) exit holes. Mating takes place soon after emergence. The adults fly, but do not feed and live for relatively short periods of three to four weeks.
Importance
This is one of the more serious food industry pests due to its widespread occurrence, its flight / dispersal capability and its ability to breach most forms of packaging. It is common in smaller shop storerooms and domestic larders, often producing spectacular infestations in old stock packets of breakfast foods and biscuits. Frequently these infestations die out as available food diminishes and fungal development in the packets takes over.
Control
Pheromone based traps or bait bags are available for monitoring. The source of infestation should be traced and eliminated. For larger or high value consignments, fumigation of the infested foodstuff source should be considered. A specialist fumigation company will generally be required to undertake the work. The application of a residual insecticide following a thorough cleaning of the infested area should form the basis of an integrated control programme.
Stock rotation should be reviewed to ensure that infestable products are turned over quickly.
Description of
Carpet Beetle
(Anthrenus verbasci)
Habitat
Common in UK, in birds' nests, domestic premises, museums. Larvae feed on fabrics, carpets, clothing, furs, stuffed specimens. Damage done by larvae, adults harmless.
Biology
Egg – larva – pupa – adult.
Eggs – up to 100 per female, laid singly on larval food of animal origin including woollen carpets, clothing, furs and museum specimens. Hatch in 10 days to 1 month.
Larvae – up to 5mm, banded appearance covered in short bristles. Known as "woolly bear". 5 moults, several months to develop.
Pupae – inside last larval skin among larval food, usually in spring. Development time 10 days.
Adults – 2–3 mm, active fliers, orange, black, white speckled appearance. Feed on pollen and nectar.
Importance
Serious pest of museum specimens, clothing and carpets in domestic situations.
Control
Remove old birds nests. Vacuum clean cracks and crevices. Residual dusts and sprays on carpets (test on small area, use non-damaging products).
Distribution and Habitat
Found commonly throughout Europe and Britain, the adult beetles fly freely feeding on pollen and nectar on flower heads during the summer months. The larvae need a high animal-protein diet and occur naturally in dry birds' nests. They appear in domestic situations infesting carpets, clothes, animal furs and skins (including stuffed specimens) and are often associated with bird nesting activity in eaves and roof spaces.
Biology
The female beetle lays the whitish eggs in or on a suitable larval food. Continuously feeding, the larvae grow by moulting several times (usually up to five) before pupating inside the last larval skin. Even the newly emerged adult remains inside this skin for a few days, before fully emerging and flying towards a pollen/nectar source. The adults are frequently found on window ledges having failed to escape from the house or other buildings.
There is usually only one generation per year, the adult females returning to buildings in the autumn for egg-laying. In cold conditions, the larvae will hibernate and resume feeding in the spring.
Importance
This species and its relatives are of particular significance in domestic properties where they will damage the fibres of carpets, bedding and clothing, animal fur, skins and leather and sometimes the heads of sweeping brushes and mops. In other situations they will frequently eat and damage stuffed animals and insect specimens in collections.
Control
Recommendations are similar to those for fur beetles. If materials are heavily infested they should be removed and destroyed. Infested areas should be cleaned thoroughly using a nozzle vacuum cleaner concentrating on removing debris and larvae from cracks and crevices. An application of a residual insecticide should then be made to the area, concentrating on treating cracks and crevices. Dust formulations, including desiccant dusts, will be effective but may be vacuumed away in subsequent cleaning
Description of
Flat Grain Beetle
(Cryptolestes spp.)
Habitat
Small beetle pest of grain and flour / feed mills in UK. Survives winter in UK in untreated buildings. Minimum breeding temperature 18–22 °C. Adults fly above 23 °C.
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Biology
Egg – larva – pupa – adult.
Complete life cycle about 3-4 weeks.
Eggs – laid singly on food.
Larvea - free living, active.
Pupae - in silken cocoons within food.
Adults - 1.5-3.5mm, brown, flattened, simple antennae. C. turcicus survives inside flour mill machinery. C. ferrugineus is a primary grain pest.
Importance
Significant pest of grain and flour mills. Contamination of flour, damage and heating of grain.
Control
Grain stores - monitor with bait bags and traps. Physical control by drying and cooling. Admixture with approved insecticides. Fumigation with phosphine by specialists. (Some tolerance to fumigants). Approved residual sprays and dusts. May be resistant to some organophosphates.
Distribution and Habitat
A number of species of this genus occur worldwide, and more than a dozen species occur through Europe. Species of this genus are pests of stored foods, primarily cereals and cereal products. In Britain, the two most common and serious pest species are Cryptolestes turcicus and C. ferrugineus . The latter has the common name rust-red grain beetle, and is primarily a grain pest. The former is more common in flour and feed mills.
Biology
Both species require fairly high minimum breeding temperatures of between 18 and 22 °C, reflecting their origin in warmer Mediterranean and sub-tropical climates. Between 40 and 50%
relative humidity is required for development with a maximum of around 90% and around 38 °c.
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Although the eggs are laid loosely amongst the larval food medium, they are slightly sticky when fresh and frequently stick to the food. The free-living larvae emerge from the eggs to attack the food immediately and after about four skin moults they form a silk cocoon within the foodstuff. Pupation takes place and the adults emerge sometime later depending, as always, on temperature and humidity. Under optimum conditions (between 30 and 35 °C for both species) the life cycle can be completed from egg through to adult in around 20 days. The rust-red grain beetle is well able to fly under high temperature conditions but in the UK is known mostly for its rapid walking activity.
Importance
C. turcicus is a well-known and serious pest in the flour milling industry where its small size and distinctly flattened shape enable it to survive within machinery. It contaminates flour, which is more serious than any possible physical damage. Additionally, it is cold-hardy and most unlikely to succumb to the normal UK winter temperatures within buildings.
C. ferrugineus . This species is predominantly a grain storage pest in the UK. It often occurs in conjunction with other primary grain pests (weevils and saw-toothed grain beetles) associated with the high temperature and humidity generated by other infestations. It is also frequently associated with hot spots in damp grain caused by dripping roof leaks and can develop into spectacularly large numbers in bulk of grain. If these populations develop in the hot, ambient conditions of late summer, the grain surface can be seen shimmering with shiny mahoganycoloured tiny beetles, many of which are flying in the air space immediately above the grain surface. This species occasionally occurs in smaller numbers and on dried fruit and some oil seeds, but it is primarily a pest of cereals and cereal products.
Control
Control is as for the majority of stored product pests, i.e. improve hygiene and treat the building fabric with a residual insecticide. Protect any high risk stored foodstuffs by either admixing an insecticide where permitted or applying insecticide in bands around stored goods. Finally store any infestable commodities in cool and dry conditions. A number of strains of Cryptolestes ferrugineus have been shown to be resistant to a range of storage insecticides and even susceptible strains can show a relatively high tolerance to some organophosphorus insecticides.
Fumigation by specialist contractors of foodstuffs or bulk grain may also be considered.
Description of
Foreign Grain Beetle
(Ahasverus advena)
Habitat
Cosmopolitan. Though more successful in the sub-tropics and tropics, it is quite common in UK and can infest farm stored grain of higher moisture content and with at least some mould growth. Requires some mould in diet.
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Biology
EEgg – larva – pupa – adult. Total life cycle 3–5 weeks.
Eggs – laid on suitable, usually mouldy, food material.
Larvae – free living and require mould in their diet, about 2 weeks.
Pupae – about 1 week.
Adults – 2–3mm, light reddish brown colour, thickened "shoulders" on prothorax.
Importance
Importance usually an indicator of poor storage conditions. A pest of commercial importance which commonly infests grain on UK farms, usually where moisture content is above 14.5% and / or where mould growth has occurred. Sometimes in association with primary grain pests.
Control
Ensure grain is stored cool and dry with no mould growth. Monitor with bait bags and traps. Admixture with approved insecticides. Fumigation with phosphine by specialists.
Approved residual sprays for structure. Do not store mouldy commodities (e.g. hay, straw) near grain.
Distribution and Habitat
A cosmopolitan species probably more successful in warmer climates, this beetle is commonly found in the UK on mouldy commodities, particularly grain of higher moisture content. It has also been found on oil seeds, cocoa beans and dried fruit. It is found on farm stored grain and, although not usually considered a primary grain pest, it is of some commercial importance as its presence may lead to rejection of grain. It may occur in mixed infestations with primary grain pests such as Cry ptolestes sp.
Ahasverus is in the same family (Silvanidae) as the saw-toothed grain beetle Oryzaephilus surinamensis but is of lesser importance. Confusingly, the appearance of Ahasverus is similar to that of the mould feeding beetles of a different family, Cryptophagidae , both of which can occur in mouldy grain, possibly leading to mis-identification. Adults possess thickened "shoulders" on the apical angles of the prothorax but, unlike the mould beetles Cryptophagus spp. , there is no tooth mid-way along the edge of the prothorax.
Biology
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The female lays eggs on suitable material and mould seems to be an important element of the diet. Larvae are six legged, pale, elongate and free living. Total development time is about three to four weeks in optimum conditions at about 30 °C.
Importance
It has been found as a pest on oilseeds such as copra (dried coconut) in the tropics and on these commodities when imported into the UK.
Its status as a grain pest in the UK is somewhat uncertain as it appears to only thrive where grain is of high moisture content and with at least some mould growth. Nevertheless, its presence can, and does, to lead to grain rejections and it should be considered at least as a "commercial" pest.
Control
Ensure grain stores are clean and free from residues before storing new grain. Monitor stores and grain with bait bags and traps. Physical control by drying and cooling, grain to reduce likelihood of mould growth. Do not store mouldy hay or straw near grain.
Where necessary used approved residual grain store insecticides to treat empty stores, or for ad mixture.
Fumigation of infested grain with phosphine by specialists. Light infestations can sometimes be reduced by (re)drying grain to reduce mould growth followed by cooling.
Description of
Larder Beetle
(Dermestes lardarius)
Habitat
Common in birds nests, also found in poultry units, animal feed mills and domestic premises. Larvae and adults feed on animal protein. Minimum breeding temperature 17°C.
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Biology
Egg – larva – pupa – adult. Complete life cycle usually 2-3 months.
Eggs – up to 200 per female laid singly on larval food, over 6 month period. Hatch in 1 week.
Larvae – up to 14mm long, dark brown banded, with distinctive bristles. Develop usually in about 1–2 months. Full grown larva bores into hard material (e.g. wood) to create pupation chamber.
Pupae – cream coloured in chamber. Develop in about 2 weeks.
Adults – 7–9mm, black with pale buff band on elytra, short clubbed antennae. Active fliers. Live about 6 months.
May be indicators of food spillage and poor hygiene in domestic or catering premises. Dermestes group includes pests of animal protein based dried food products, animal feeds, skins and hides.
Importance
In poultry units larval pupation chambers may cause structural weakening of timbers and damage to polystyrene insulation.
Control
Good hygiene, residual sprays. In poultry units carefully applied insecticide bands to kill migrating larvae or physical barriers to prevent migration.
NB Care needed to avoid killing beneficial beetles Carcinops (useful in housefly control) in deep pit houses. Do not spray manure other than with "selective" larvicides such as cyromazine.
Distribution and Habitat
The larder beetle is one of a group of similar beetles in the genus Dermestes that are known collectively as hide beetles. It is found throughout Europe and is very widespread in the UK. All Dermestes species larvae feed on high protein diets, preferring material of animal origin. They occur naturally in birds’ nests and many species have found intensive poultry houses to be an ideal substitute.
Biology
The adult female beetle lays up to 200 eggs that hatch in about a week into small bristly larvae. In less than two months the fully fed larvae (after several skin moults) migrate from the food source and seek pupation sites nearby. They make pupation chambers by tunnelling into suitable adjacent materials, and have a particular attraction for wooden panelling and structural timbers. In poultry houses and piggeries the larvae may also chew into polystyrene and urea foam insulation materials as alternative pupation areas. The total duration of the life cycle depends mainly on temperatures, with a minimum of 17 °C and an optimum of 24 °c and takes from 8 to 12 weeks.
Importance
These are serious pests in industrial and domestic kitchens, particularly around food cupboards, cookers and refrigerators. They are also significant pests in poultry houses and occasionally in piggeries.
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Their occurrence in kitchens is usually associated with poor hygiene that allows them to breed successfully on food scraps. The adult beetles fly readily, and are attracted at night to illuminated windows, creating new infestations in the kitchens of flats, and staff canteens on the upper floors of high-rise buildings.
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Their significance in poultry units and piggeries relates to the fully grown larvae that bore into structural timbers and insulation in the search for pupation sites. Serious structural damage and weakening of supporting timbers can result and the insulation value of expanded polystyrene sheeting can be reduced significantly. They also tunnel into glass fibre wadding, seemingly with no adverse effect to the wadding.
Control
The larder beetle and other hide beetle species may occur within domestic situations, commercial kitchens and animal houses. Control of all species is similar but the methods used will vary according to the situation in which they are found.
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Domestic and industrial infestations:
In domestic situations or industrial kitchens, an integrated control programme of cleaning and spraying with a residual insecticide will control most infestations, although eradication of widespread infestations may take some time. If pupation has occurred nearby, a subsequent re-treatment or the use of strongly residual active ingredients and formulations may be necessary. If empty birds' nests have been an infestation source they should be removed.
Most residual insecticides will be effective if applied thoroughly to the structure, concentrating on the treatment of cracks and crevices with liquid or dust formulations. Residual pyrethroid, carbamate and organophosphorus active ingredients have all been shown to kill hide beetles, although it may be that larval stages are more tolerant than the adult stage.
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Animal units:
In infested animal units, control can be very difficult to achieve when larvae and adults have penetrated insulation materials (e.g. polystyrene, fibreglass). Application of a residual insecticide to the outer surface of the insulation will prevent further immigration into the structure but will not halt the activity of insects protected within the insulation material.
It is important to isolate the beetles' main breeding area (in animal wastes) from the vulnerable areas of insulation material, by physical or chemical methods. Metal plates can be built into concrete block walls and pillars to protrude some 1O–15cm out from the wall surface, and deflected downwards to form a physical barrier to the beetles' progress up the wall or pillar
An insecticidal "barrier" may be formed by applying a residual insecticide e.g. alphacypermethrin in a band along the base of walls and pillars. This is best applied when the house is empty, after manure has been removed and cleaning has been carried out. Insects attempting to migrate should contact a lethal dose of insecticide as they cross the band.
Conventional insecticides in deep pit poultry houses and sometimes other types of animal house to control hide beetles must be carefully applied to avoid killing beneficial beetles living in the manure. Beetles such as Carcinops are predatory on housefly larvae and are often essential for the maintenance of good fly control. Insecticides (other than selective larvicides such as cyromazine- see control of houseflies in deep pit houses) should not be applied directly to manure. There may also be problems with using quick acting "knockdown" insecticides within the pit areas of deep pit houses for the same reason.
Other Species
The leather beetle (Dermestes maculatus Degeer), black larder beetle (Dermestes haemorrhoidalis Kuscer), and Peruvian larder beetle (Dermestes peruvia nus Laporte de Castelnau) are all similar dark brown/black beetles. They are distinguished variously by the presence or otherwise of whitish patches at the sides of the thorax and the shape of the terminal points of the wing cases when seen from underneath.
Their occurrence, food requirements and general biology are very similar to the larder beetle although their relative importance in the domestic and industrial kitchens, poultry and piggery units varies, as does their geographical distribution and frequency of occurrence.
Description of
Lesser Mealworm Beetle
(Alphitobius diaperinus)
Habitat
Tropical origin but now widespread as an indoor pest in UK. Imported on oilseeds, cereal products, bones. Found in animal houses, particularly deep pit and deep litter poultry houses where may be a pest but also aids housefly control by aerating manure.
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Biology
Egg – larva – pupa – adult. One generation per year in unheated buildings but several in deep pit house, (4–6 weeks to complete life cycle).
Eggs – up to 300 laid among larval food material. Hatch in about 1 week. Larvae – up to IC)mm, banded appearance (pale and dark brown) with "tail horn", active, free living. Develop in 1–2 months with 4–6 moults. When full grown seek pupation site and may cause damage.
Pupae – in chamber in building structure (such as polystyrene insulation) or dry poultry manure. Develop in about 1 week.
Adults – about 6mm, shiny dark brown/black, oval, medium length antennae. Will fly in hot weather. Usually live 1–2 months.
Importance
Sometimes pest of animal feeds. In other situations often only a nuisance but full grown larvae may cause damage to insulation in pig and poultry units. May reach high numbers in poultry manure. May affect birds in deep litter houses. In deep pit houses adults may migrate into cage area and become nuisance but larvae and adults may be of benefit in manure by assisting aeration and drying, aiding housefly control.
Control
Difficult in some situations. In deep pit houses may not be necessary or partial control only. Residual insecticides in some situations but do not use directly on poultry or pig manure. May occur in association with the beneficial beetle Carcinops spp. and care must be taken not to use products that would kill this species. The "selective" larvicide, cyromazine, used for housefly control does not affect beetles.
Distribution and Habitat
Although of tropical origin, this species is very widely spread through Britain and Ireland but always indoors. It has been commonly imported into Britain on a wide variety of products including oilseeds and cake, rice-bran, cereal products and even bones. It is a common pest in animal feed mills and of recent years has assumed major significance as a pest species on poultry farms, especially in deep-pit egg production units.
Biology
The adult female beetle lays up to 300 eggs over a few weeks, loosely depositing them amongst the food material for the resultant larvae. Around a week later the thin pale cream larvae hatch and immediately burrow amongst the food medium, eating voraciously. Over a period of one to two months, and between four and six moults, the larvae develop to a maximum of about IC)mm in length with noticeable darker brown banding across the upper surface of a pale brown body. They have a single "tail horn".
When nearly full-grown the larva burrows into some nearby material to form a pupation chamber where the pupa is formed without a protective cocoon. In poultry houses, and sometimes older animal feed mill structures, the pupation chamber will be made within the structure of the building. This may lead to significant structural damage over a number of beetle generations.
Usually within a week the adult beetle emerges and can then live for a further one to two months, with a maximum recorded age of over a year. In cooler indoor conditions, which often prevail in feed mills, only one generation per year is possible. In the enclosed and protected warm environment of piggery and poultry units which are frequently close to the optimum conditions for this species (28 °C and more than 75% relative humidity) the complete life cycle will occur in four to six weeks.
Importance
In many indoor situations this species is little more than a nuisance. Some years ago when oil cakes and rice-bran were commonly imported for the animal feed industry Al phitobius was a frequent pest and often necessitated costly fumigation and residual treatments. This pest's significance is now primarily in the poultry and pig industry. It is the habit of the beetle larvae prior to and during pupation that causes the damage. Poultry units utilising expanded polystyrene sheeting for insulation perhaps suffer the most damage, with a significant loss in insulation value over a period of a few years where the beetles are allowed to breed unchecked. The populations can reach vast numbers and in indoor free-range or litter situations the beetles can seriously affect the health and welfare of chicks and hens. They are voracious eaters quite capable of turning carnivore and attacking and killing sickly or otherwise out of condition birds. Even the presence of such large numbers of beetles and larvae in the litter can cause birds to become restless, unsettled and flighty. They can also be responsible for spreading some poultry diseases. Their saving grace in poultry units is a seemingly healthy appetite for fly larvae (maggots), although it is not generally accepted that they are capable of successful biological control. They may also assist in the aeration of poultry manure in deep pit houses.
Control
The burrowing behaviour of this beetle makes eradication of heavy infestations almost impossible in housed animal units. Both late larval and adult stages will burrow into insulation material and earth floors, protecting themselves from contact with insecticide treatments. In addition, resistance to some organophosphorus insecticides has been confirmed in some UK strains. Alphacypermethrin is usually effective.
Management of populations of the beetle is generally attempted, following thorough cleaning out of manure and food residues, by application of a residual pyrethroid or organophosphorus insecticide to the structure of the building. In some situations a banding treatment of walls and pillars will reduce migration of large numbers of beetles into the structure. This is best applied before beetle populations build up significantly, and before terminal clear out of the animal wastes which generally triggers extra migrations of the beetles and larvae.
Following application of a residual insecticide to the structure after clear out, it may be of benefit to increase the temperature of the animal house to activate beetles onto the treated surfaces, before the house is restocked. Projecting metal proofing strips, angled downwards and built into the walls of intensive animal units can reduce the upwards migration of beetles.
Conventional insecticides in deep pit poultry houses (and sometimes other types of animal house) to control lesser mealworm beetles must be carefully applied to avoid killing beneficial beetles living in the manure. Beetles such as Carcinops are predatory on housefly larvae and are often essential for the maintenance of good fly control. Insecticides (other than selective larvicides such as cyromazine- see control of houseflies in deep pit houses) should not be applied directly to manure. There may also be problems with using quick acting "knockdown" insecticides within the pit areas of deep pit houses for the same reason.
Description of
Plaster Beetle
(Lathridiidea species)
Habitat
Common in UK feeding on moulds and fungi. On rotting vegetation outside and damp situations inside. Also damp grain, hay and straw. May feed on moulds on damp plaster, hence name. Preferred temperature 20 °C.
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Biology
Egg – larva – pupa – adult.
Eggs – laid singly on mouldy materials. Hatch in about 1 week. Larvae – feed on moulds. 3 moults, develop in 3 weeks.
Pupae – free formed (no cocoon) near food. Develop in about 1 week. Adults – small 1.5–2.5mm. Feed on moulds.
Importance
Harmless outside, usually only a nuisance inside. Possible contaminant in food industry. Indicator of mould growth and damp grain
Control
Humidity, moisture content control. Residual insecticides.
Distribution and Habitat
All members of this family feed on moulds and fungi and require damp, high humidity conditions to exist. Many are found out of doors, beneath loose bark, amongst dying and rotting leaves, and frequently in stacks of sawn timber. They occur indoors wherever suitable conditions exist. About 35 species have been recorded in food storage and domestic situations in the UK.
Biology
Eggs are laid singly amongst and around a suitable substrate, which must include mould and/or fungal hyphae. The larvae hatch about a week later, and commence feeding on the hyphae and fruiting bodies. Depending on the species, and physical conditions (especially temperature) the larval phase may take up to three weeks and three or four moults. The pupae are formed freely, i.e. no cocoon, in suitable cracks and crevices of the adjacent area. Usually within a week the adult beetle has emerged from the pupa, and continues feeding on the same substrate.
Around 20 °C seems to be an optimum for most of the Lathridiids, at which temperature they
can achieve complete metamorphosis in just over a month. Many of the species can fly, but
only at higher temperatures.
Importance
Out of doors these beetles are of no significance whatsoever. Indoors they can present significant nuisance problems and in food factory and storage situations may be serious contaminants. Domestically, these beetles are common in lofts, frequently associated with birds' nests. Within the living areas, they will occur wherever suitably damp and slightly mouldy conditions exist. This often restricts them to bathrooms, where they may occur in some numbers beneath carpets and linoleum, and behind fitted bath panels. They often occur in very small numbers in the kitchen and pantry until suitable conditions are created when they can breed rapidly and produce large numbers over a short period of time. New buildings, with fresh plaster on the walls, may suffer "flash infestations" as the damp plaster becomes slightly mildewed and attracts and supports a population of plaster beetles. Once the plaster dries out the beetles disperse.
Some building methods from the 1960s onwards have included compressed straw-board with a fine paper surface finish as an insulation and light structural material. If used in areas subject to high humidity and the surface coating is broken, internal infestation of booklice (Psocoptera) and plaster beetles may develop, feeding on the moulds generated in the small inter-straw spaces. Where this material is used as a filling in stud walling, the beetles may exit through natural breaches, such as light switches. Food storage premises frequently carry a permanent, light residual infestation of plaster beetles. They usually occur on the structure of the building but can contaminate stored food packaging. They are well known in flour storage, especially if the flour is packed in multi-wall paper sacks that are allowed to become slightly damp. The flour dust on the outer surface of the bags attracts atmospheric moisture that permits a small development of moulds and fungi and plaster beetles infest.
Control
A residual insecticide application should quickly control adult beetles if control of humidity cannot be achieved. Bendiocarb or permethrin will be effective as will most other public health and hygiene insecticides. Some organophosphorus and carbamate active ingredients may hydrolyse quickly on fresh plaster.
Description of
Rust-Red Flour Beetle
(Tribolium castaneum)
and Other Flour Beetles
Habitat
Very common world wide on stored foods. Probably the beetle most commonly imported on stored products. Also in animal feed and flour mills. Feeds on wide range of materials including cereals, cereal products, nuts, dried fruit, animal feeds. Rarely a farm grain pest in UK.
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Biology
Egg – larva – pupa – adult. Total life cycle 1–2 months.
Eggs – up to 450 per female over several months on larval food. Hatch in about 1 week.
Larvae – narrow, yellowish-white, pale bands, free living. Develop in 3–5 weeks .
Pupae – free (not in cocoon) in larval food. Develop in 5–10 days.
Adults – 3–4mm, shiny rust-red colour. Often found in groups, attracted by aggregation pheromone.
Importance
Significant pest of flour and animal feed mills, imported foodstuffs. Can cause tainting of flour. Not a regular grain pest in UK but can infest warm grain.​
Control
Good hygiene. Monitoring with bait bags, pheromone traps. Residual organophosphates and pyrethroids. Fumigation of foodstuffs by specialist contractors .
Distribution and Habitat
Found worldwide but always in association with stored foods. Widely distributed in the UK with endemic populations supplemented annually by importation of various stored products. Especially common in animal feed mills and becoming more common in flour mills.
Biology
The female beetle lays up to 450 eggs over a long period of time, but this is variable according to the localised temperature. The eggs are loosely laid within a food material of the larvae, and hatch within the week. The larvae feed on a wide variety of stored foods but favour cereals and cereal products. They are also commonly found on groundnuts, dried fruits, spices and nuts and were at one time a familiar feature on imported oil cake and rice bran.
The larvae take about four to five weeks to develop into a freely formed naked pupa, amongst the foodstuff. Five to 10 days later the adult beetle emerges. These are long-lived, sometimes reaching 18 months in age. The entire life cycle will be completed within a seven week period, at temperatures around 25 °C. Since this species thrives in warm conditions (as would be expected with an insect of tropical origin) in higher temperature areas (e.g. bakeries) the duration of the life cycle can be reduced to three or four weeks.
Rust-red flour beetle adults and larvae show cannibalistic tendencies, especially in high population density situations. The female beetles are known to emit "aggregation pheromones" and this inevitably leads to clumping of the adults, especially noticeable late in the afternoons. This habit is part of their mating and distribution behaviour and in the tropics the species is well known for its late afternoon mating and dispersal flight. Food warehousing overseas is difficult due to the ease with which T. castaneum flies from shed to shed. In this country, distribution and dispersal is almost always by walking and being carried by vehicles.
Importance
This species is highly significant as a primary and successful pest in the milling industries. It has an added importance due to its habit of tainting foodstuffs with bitter secretions from glands on the abdomen of the adult. The taint remains with the food and in the case of flour, this tainting may seriously affect the rising of the dough. Although the beetle is found in grain storage, it is not the first invading species, preferring grains that have already been damaged by other species. It then preferentially attacks the germ. It requires a much higher temperature (20 °C) than many of our endemic insect pests of grain and infests bulk grain once this has heated because of other insect activity.
Control
As with most storage pests, improvements in hygiene linked to the use of residual insecticides are the key to successful control. Structural improvements may be necessary to reduce or eliminate insect refuges and machinery may have to be dismantled to reach infestations. While a range of residual insecticides will generally control the rust-red flour beetle, resistance to a number of organophosphorus, carbamate and pyrethroid insecticides has been recorded in strains throughout the world. Thorough treatments with one of the more recently developed organophosphorus or pyrethroid residuals should overcome all but the most stubborn infestations .
Fumigation of large food consignments by a specialist contractor may also be considered.
Other Species
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Confused Flour Beetle - Tribolium confusum , 3–4mm in length, mahogany-brown, elongate / parallel sided, and slightly flattened. Very short antenna without a distinct "club". The larva is almost identical to that of the previous species (T. castaneum) . This species is endemic in the UK although also found worldwide. It is more cold-hardy than the previous species and tolerant of extremely low humidities. Slower breeding, the minimum life cycle duration of about five weeks may be extended to 18 weeks at lower temperatures. Adult longevity is similar with up to 18 months possible. This is the more common of the two species in British flour and animal feed mills, and produces similar tainting of the raw and finished materials. The two species will not interbreed.
Control
Control is as for the rust-red flour beetle, but without the extra problem posed by insecticide resistance .
Broad Horned Flour Beetle - Gnatocerus cornutus (previously known as Gnathocerus) , and Slender Horned Flour Beetle - Gnatocerus maxillosus. These species are related, with the former being more frequently found, although neither are common. They are slightly larger than Tribolium castaneum, about 4mm, but otherwise generally similar except that the mandibles (jaws) of the adult males are enlarged, with those of G. corn utus being broader as implied by the common name.
G. cornutus is a minor pest of flour and cereal products, sometimes found in flour and feed mills or food factories. Occasionally a pest of grain although very rarely in the UK. Minimum breeding temperature is 16°C, optimum 24 – 30°C. Life cycle can be completed in two months in ideal conditions.
G. maxillosus is occasionally found on imported foodstuffs.
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Small Eyed Flour Beetle - Palorus ratzeburgi . Slightly smaller than Tribolium castaneum but similar in colour and distinguished by having small round eyes which are not partly divided by a ridge (as is the case in Tribolium spp .) . Both adults and larvae feed on damaged and mouldy grain, or on cereal products such as flour. They are a minor pest of flour or feed mills.
Description of
Saw-toothed Grain Beetle
(Oryzaephilus surinamensis)
Habitat
Widely distributed in temperate and tropical zones. Significant grain pest but also on many other stored foods. Survives winter in untreated buildings, grain stores in UK. Minimum breeding temperature 17 °C.
Biology
Egg – larva – pupa – adult. Complete life cycle 1–3 months.
Eggs – Up to 400 per female, 6-10 per day on larval food. Hatch in a few days
Larvae – active, free living. On cereals, feeding usually on damaged grains and other food stuffs. Develop in 2–6 weeks.
Pupae – in cocoons among foodstuff. Development few days to 2 weeks approx.
Adults – 2.5–3.5mm, dull brown, slender appearance, 6 "teeth" on sides of thorax.
Importance
Most important UK grain pest but also on cereal products, nuts, dried fruit. Causes grain heating (leading to "hot spots" and mould growth), damage and loss of germination. Contamination and damage to other foodstuffs.
Control
Grain stores – monitor with bait bags and traps. Physical control by drying and cooling. Admixture with approved insecticides. Fumigation with phosphine by specialists.
Other premises – survey with bait bags. Removal of small consignments. Fumigation by specialists for larger consignments.
All stores – approved residual sprays and dusts. May be resistant to some organophosphates.
Distribution and Habitat
The larder beetle is one of a group of similar beetles in the genus Dermestes that are known collectively as hide beetles. It is found throughout Europe and is very widespread in the UK. All Dermestes species larvae feed on high protein diets, preferring material of animal origin. They occur naturally in birds’ nests and many species have found intensive poultry houses to be an ideal substitute.
Biology
The mated adult female beetle lays between 100 and 400 eggs in and amongst the larval food materials, over a period of 6 to 10 weeks. The eggs hatch into free-living larvae that immediately begin to attack the adjacent food. In bulk grain storage, the larvae will attack broken or damaged grains and can only enter whole grains if the testa has been breached. The germ part of the grain is usually attacked first. The larva moults on average four times before the final change into a free-formed pupa. Total developmental time from egg through to adult can be as short as 20 days at around the optimum temperature of 35 °C but at lower temperatures e.g. 20 °C up to three months may be required. The minimum breeding temperature for this species is about 17 °C.
Importance
Although found in other parts of the food trade, for example nut storers and processors and dried fruit importers, it is in bulk grain storage that this beetle has assumed prominence. The rate of breeding under ideal conditions is so high that massive infestations may develop within bulks of grain causing huge physical damage. The classic "hot spot" frequently occurs, where generations are produced more and more rapidly as the localised temperature within a grain bulk rises and this gives rise to translocation of moisture with consequent condensation in the upper layers of grain. Rapid and serious mould development takes place and the surface of the grain usually begins to sprout. At this point the centre of the "hot spot" may have reached 40 to 50 °C and those insects which can migrate move away from the hottest part and spread the infestation. It is not unknown for grain to catch fire when broken open to be moved and the inrush of oxygen allows the slowly charring grain to ignite.
This species is commonly imported on a wide range of food products from many countries of the world. Its greatest pest significance is with cereals and cereal products, including rice, and sometimes with dried fruit. It is a major pest in the processed food trade attacking many different packaged commodities. Although it cannot easily penetrate packaging materials by chewing entry holes, it is very adept at invasion through the smallest of gaps in the construction of the packages.
Control
In domestic or food storage situations the source of the infestation must be determined and removed. Long standing infestations of this beetle will generally be widely dispersed making complete control very difficult in the short term. Bait traps can be used to monitor for the presence of wandering insects and they can also help pinpoint harbourage areas which may have been missed by treatment. A number of residual insecticides can be effective against this beetle even though there are indications of organophosphorus resistance in a number of strains in the UK.
In grain stores, treatment of the structure of infested buildings will, in itself, be unlikely to prevent infestations in new grain. In such cases, a combination of physical control by cooling and drying the grain (to 15 °C and 15% mc, or below) and chemical control using a residual insecticide admixed with the grain is necessary. Chemical protection of grain that is stored cool can remain effective for more than 12 months.
Description of Yellow
Mealworm Beetle
(Tenebrio Molitor)
Habitat
Common in UK as omnivorous scavenger in birds’ nests, on droppings or dead birds and on general residues in attics and cellars. Larvae used as fishing bait.
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Biology
Egg – larva – pupa – adult.
Eggs – up to 500 per female, laid in batches on food material. Hatch in about 2 weeks.
Larvea - up to 3 mm long, yellow and brown banded. Free living on cereal products, birds nest detritus and general scavengers. Take up to 1.5 years to develop.
Pupae – away from larval food, free formed (no cocoon). 3–4 weeks to develop.
Adults – quite large, 15mm, dark brown / black. Fly readily and may enter buildings at night.
Importance
Minor pest usually indicating poor hygiene or debris in roof spaces and cellars.
Control
Good hygiene and remove residues or debris. Residual insecticides if required.
Distribution and Habitat
Widespread throughout Britain, the adult beetles fly and are attracted to light, aiding distribution, which sometimes results in their occurring in unusual places. Usually in association with birds' nests or long standing food residues and other debris in stores and
Biology
The female beetle lays up to about 500 eggs over a period of weeks, often in batches, and the sticky egg surfaces soon become covered in dust and debris.
Two weeks or so later (depending especially on temperature) the young larvae hatch from the eggs and immediately start feeding on any suitable food material. Their preference is for cereals, or cereal-based products, but they are virtually omnivorous and quite adept at scavenging on dead insects and the corpses of birds and rodents. This is a slow breeding species and the larvae may take anything up to one and a half years to reach maximum size, passing through 10 to 20 moults. At around 28 to 3 mm in length, they crawl away from the food material and gradually shorten and thicken. The pupa is formed freely wherever the larva settles and shows many external features of the subsequent adult insect. Three or four weeks later the adult beetle emerges and darkens in colour over the space of a day into an almost black and shiny mealworm beetle.
Importance
This species seldom breeds in large numbers and even under the best conditions takes a full year for complete development. It is a scavenger and not a significant primary storage pest. When found in food manufacturing and storage premises (quite common in the basement areas of feed and flour mills) it is indicative of a long-standing neglect of hygiene. When it occurs in corner shop store rooms, it may well be as a result of migration from birds' nests in the eaves and structure of the building. Domestically, if found in ones and twos, these may be casual arrivals attracted to open illuminated windows at night. If found in greater numbers, a local breeding site is present which may be a birds' nest or a dead bird lodged in a chimney or in the loft. If on the ground floor, a thorough investigation of the pantry and associated kitchen areas should be made.
Control
In view of the beetle’s long developmental period infestations are generally indicative of poor
hygiene and the presence of old food residues. Cleaning of infested areas and spraying with a residual insecticide should control the problem.
Other Species
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The Dark Mealworm Beetle (Tenebrio obscurus) . The adult dark mealworm beetle is almost identical in size, shape and colour to the yellow mealworm beetle. The larvae are easier to separate: whereas T. molitor larvae are a straw yellowish colour, T. obscurus larvae have a brownish banding to each segment. The habitat and food preferences are similar to the preceding species but the distribution of T. obscurus in Britain is more restricted and it is considered to be an uncommon species.
