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Life Cycle & Description
Description of Blowflies
and Flesh Fly
Bluebottle - (Calliphora vicina and Calliphora vomitoria)
Common worldwide and in association with humans. Adults active fliers. travel several miles. Bluebottle will enter buildings readily to find breeding sites. Breed in carcasses, meat, offal, meat products.
Egg – larva – pupa – adult.
Eggs – whitish, 1.5mm, several batches of up to 180 on carcasses or meat. Hatch usually in 1–2 days.
Larvae – whitish, legless maggots up to 18mm long in groups on carcass/meat. 3 moults, usually develop in a few days (average 1 week). Move away from food when fully developed.
Pupae – inside reddish puparia in soil or dry areas. Develop in 1–2 weeks.
Adults – llmm, deep metallic blue. Large red eyes. Acute sense of smell.
Potential disease transmission. Pest of meat industry, slaughter houses. May breed on dead rodents, birds within buildings. Also valuable re-cyclers of dead animal material.
Fly screen windows and doors, strip curtains, good hygiene, covering potential breeding materials. Residual or knockdown insecticides.
Electronic fly killing devices.
Distribution and Habitat
Species of the family Calliphoridae are found worldwide and always follow a very similar life history. Bluebottles primarily breed on dead and decaying animal matter, preferably carcasses or meat offal. Although very common in the wild, they are also frequently associated with some human activities.
After emerging from the pupa and expanding and drying their wings, adult bluebottles mate and four to five days later the female begins egg laying. In domestic and food factory situations this is described as "blowing" or the depositing of the eggs in clusters on any fresh or older meat, meat products and offal or even on excrement. Freshly killed animals and game birds will be singled out for "blowing" by the extraordinarily acute sense of smell of the adult female fly.
The elongate eggs, which are 1.5mm long and creamy-white, usually hatch in less than a day. Almost immediately the larvae burrow into the food supply by creating cavities due to the partial dissolving of the food material by their own enzymes and by the natural bacterial action on dead and decaying meat. They moult about three times during their developmental period, which may last about a week, and at their maximum size are the well-known "gentles" or maggots used and favoured by anglers.
Wherever possible the fully grown larvae migrate from the food material and search for a suitable pupation site in the nearby soil. Where this is difficult or impossible, for example in food factory refuse areas where dustbins or other containers have become infested, the maggots will wander quite considerable distances (anything up to IOO m) in search of suitable pupation sites. Whereas the larva grows to about 18mm, the pupa is considerably shorter at about I0 mm, and a dull mahogany brown in colour.
Under average conditions the adult fly emerges about two weeks later. The generations, which are still developing with the onset of winter, usually hibernate as fully grown larvae. Pupation then occurs in the early spring and adults emerge sometime later. In mild winters adult Calliphora may be seen in January or February and these almost certainly have emerged from pupae formed in the autumn.
In country districts bluebottles or blowflies perform a very valuable function in assisting with the removal and recycling of dead animals and birds. Even on poorly maintained refuse tips, bluebottle breeding may not cause any significant problems. Given the uncanny ability of the female flies to search for and find suitable meat-based food in human establishments and their well documented ability to spread disease organisms, they form a very significant problem in meat processing plants, commercial canteens and food preparation areas and even in domestic kitchens. They have a well known heavy droning sound in flight and are not deterred from entering cool, dark areas in search of larval food. They can infest or "blow" even "concealed" meat and meat products rendering these unsuitable for human food. Localised infestations within buildings may sometimes occur following rodent control operations when carcasses attract flies.
Greenbottle - (Lucilia spp.)
Greenbottles belong to the same family as the bluebottles, Calliphoridae , and are collectively called blowflies. Several species of Lucilia are commonly found in very similar situations to bluebottles, although they are smaller and very easily distinguished by the striking bright metallic green colour of the thorax and abdomen. Considerable size variation occurs in greenbottles, which is a result of the quality of the food supply of the larvae and the general favourability of the breeding conditions, including moisture and temperature. Adults often sun themselves outside on fence posts and house walls.
Unlike bluebottles, greenbottles are seldom attracted indoors and rely much more on the dead bodies of animals and animal excrement for breeding sites. The eggs, egg-laying pattern and larval development are all very similar to bluebottles but usually slightly slower due to their dependence on outside ambient conditions. Although not having quite the same nuisance value to humans as the bluebottles, it is doubtful whether they are considered by most people to be beneficial. There are many records which show that the Lucilia larvae can be used successfully to clean up suppurating wounds, where the larvae remove only the decayed tissue and allow a healthy and quick re-generation of new flesh.
Flesh Fly - (Sarcophaga spp.)
This species also belongs to the family Calliphoridae , and is usually at least as big as the large bluebottles. It is clearly distinguished by its overall grey colouring, the thorax with dark longitudinal lines, and the abdomen with a slightly shifting chequered or tessellated appearance. Whereas bluebottles are a rounded oval shape, flesh flies are more elongate and have particularly noticeable large feet, with powerful claws that grip well on human skin.
The larvae of the flesh fly also feed on carrion and decaying animal matter. Instead of laying eggs on the larval foodstuff the female flesh fly allows the eggs to hatch within her uterus and she gives birth to live young larvae. These immediately burrow into the food material ejecting an enzyme-laden fluid to dissolve the meat and provide themselves with a liquid food supply. The larvae of Sarcophaga have a small circle of breathing tubercles at the tail end, which enables them to float vertically, head down, feeding in the liquid medium and breathing at the same time. The fully grown larvae migrate, preferably into soft soil, to pupate and the adult fly emerges by forcing the end cap off its puparium by means of its expandable ptilinum. By rapidly expanding and contracting this hydraulic ram, the adult fly is able to emerge through the soil layer, finally withdrawing the ptilinum which then hardens on the front face of the fly to form the typical "ptilinal suture" used so frequently in the identification of this major group of flies.
Flesh flies are commonly found throughout the summer investigating dustbins and other suitable breeding sites outdoors. They seldom enter buildings and do not exhibit the same searching habit as the bluebottles. They pose less of a threat in domestic and commercial kitchens, although meat processing plants can still suffer their depredations because of ineffective offal and waste clearance.
Bluebottles and other blowflies (Calliphora species). As with most fly species hygiene and proofing are the most important factors in achieving effective control. In food manufacturing premises windows should be screened with fly mesh and high risk meat products should be covered to prevent egg laying. Animal waste should be covered and removed frequently.
Residual insecticides may be used on walls and surfaces where large numbers of adults may rest. The source of the adults, perhaps a nearby dead bird or mammal, should always be sought to prevent repeat breeding. Aerosol or misting space sprays based on pyrethroids can be used to knockdown and kill visible adults quickly. Electrical fly killers using UV light may also be used in certain situations.
Greenbottles. The principles of control above also apply to greenbottles. If greenbottles are developing on live sheep (termed "flystrike") animal medication will be required and specialist advice should be sought.
Description of Cluster Fly
Adults live harmlessly out of doors in summer but may enter buildings (usually roof spaces and lofts but also through windows into rooms) in autumn to hibernate, sometimes in vast numbers. Other unrelated species may also cluster.
Egg – larva – pupa – adult.
Eggs – laid in damp soil, rotting vegetation. Hatch in about a week. Larvae – soon after emergence seek out and parasitise earthworms which are eventually killed. Development several weeks.
Pupae – in soil.
Adults –6mm long, blackish, with fine golden hairs on thorax (sometimes rubbed off). Often 2 generations per year.
May be severe nuisance if large numbers of adults enter inhabited parts of buildings. Some buildings infested each autumn year after year.
Very difficult. Control of pre-adult stages not possible. Sealing entry points difficult. Vacuum cleaner to remove adults. Residual sprays or knockdown space sprays. Do not treat if possibility that bats are present in roof space. (consult the relevant Statutory Nature Conservation Authority) .
Distribution and Habitat
Found commonly throughout Europe and the UK. The common name refers to its habit of clustering and hibernating in numbers in buildings.
The adult female lays eggs loosely on and around damp soil and beneath dead and rotting leaves. After about a week the larvae hatch from the eggs and actively seek earthworms to which they cling and then bore through the body wall. The conventionally shaped fly maggots develop inside the earthworm. Later instar larvae have been observed to push their hind ends back through the earthworm body wall to allow their breathing spiracles to gain access to the free air. At or near to the death of the earthworm the larva bores its way out again and pupates in the soil.
Since this is a free-living "field" insect, the life cycle is very dependent on weather conditions. . In Britain it seems that two generations per year are common and in hot summers up to four generations per year might be possible.
The adult flies, resplendent with their thorax clothed in golden hairs (which often rub off), feed
on the nectar of garden and wild flowers.
During the summer and early autumn these flies are of no consequence. As the season cools they seek shelter in nooks and crannies in houses and other buildings. As temperatures drop they search for more protection and frequently form vast clustering masses in roof spaces and lofts. It has often been observed that the same house or building in a row of similar buildings will be chosen year after year.
Such large aggregations of flies do produce a rather sickly smell and, if warmed-up accidentally or artificially during their hibernation, may emerge rather lazily and create some consternation among people using the building. This has occurred commonly in church halls, domestic bedrooms and has even been recorded as a problem of fly-contaminated switch-gear in heated automatic telephone exchanges.
Autumn Fly (or face fly) (Musca autumnalis)
A fly very similar to the housefly in appearance but distinguishable by its clearly defined striped grey and yellow abdomen and by the eyes of the male which almost touch along the centre of the head.
The female autumn fly lays its stalked eggs on animal dung in fields and the larvae develop within the dung and pupate in the surrounding soil. The adult flies tend to feed on body secretions of stock in the fields and have been recorded drinking blood, although they are incapable of piercing animal and human skin. Their hibernating behaviour is very similar to the previous species and they frequently form mixed populations inside suitable buildings.
Green Cluster Fly (Dasyphora cyanelIa)
In the same family (Calliphoridae) as the quite common greenbottle Lucilia and very similar in appearance, Dasyphora can usually be distinguished by its fairly distinct, two longitudinal dark stripes on the thorax.
This is another species where the larvae develop within the dung on which the adult female has laid her eggs. As with all outdoor insects, the life cycle is very dependent on weather conditions: from egg to adult may take anything from six to 10 weeks, and the adults are usually active from early summer right through to the onset of cold late autumn weather. The seeking of hibernation sites is similar to the preceding species and the green cluster fly is frequently a member of mixed swarms in roof spaces.
Yellow Swarming Fly (Thaumatomya notata)
This is a much smaller species of hibernating fly, seldom being longer than 3mm, with a typical chloropid fly appearance –fairly large rounded wings in relation to its small yellowish rounded body with black markings. It may be confused with fruit flies.
It is another outdoor species that lays its eggs in the soil around the roots of grasses. The young larvae hatch from the eggs and specifically parasitise species of root aphids. Two generations occur in most years. In warmer seasons those adults which emerge early attempt to hibernate in much the same way as the species above, forming large swarms in domestic and other roof spaces, especially in church belfries.
The Window Fly (Anisopus fenestralis)
The adult fly is about 3–4mm in length reminiscent of a small crane fly, with noticeable long spindly legs and fairly prominent antennae. The wings, with a fairly complex venation, may sometimes be seen to have cloudy grey / brown patterns. This is one of several species of flies commonly found to infest sewage works sometimes reaching very large numbers and producing giant swarms. It is one of the more common species to enter houses and other buildings, frequently being seen on window ledges and frames. The adults will attempt to hibernate with the onset of colder autumn/winter weather but only a small proportion of those will survive the winter. Of greater significance is the common habit of the female fly to lay eggs in any damp situation, often resulting in foodstuffs in the domestic pantry becoming infested .
Control methods for the above cluster and swarming flies have been little researched and they are often ineffective or, at best, incomplete. It is often not possible to prevent flies from entering premises or to persuade affected householders that the flies, while a great nuisance on occasion, are unlikely to represent a health risk, do not breed indoors and are not indicative of poor hygiene. Control of the flies outdoors in their breeding areas is considered impractical.
In recommending a combination of physical and chemical control methods, it is recognised that proofing against fly entry is seldom 100% effective. Caulking around window frames and sealing other entry points can contribute greatly to control. It is difficult to use insecticide in and around "unsealable" entry points to some buildings, e.g. thatched roofs or under tiles or slates, but in some situations where recurrent problems have been experienced, prophylactic dusting of likely access points can be partly effective.
Once the flies are inside, e.g. in a loft or attic, control is relatively simple with both physical methods and a range of insecticides and formulations. Occasionally a vacuum cleaner (nozzle type) can be used as the sole control method where aggregations exist within reach and the collected flies can be disposed of in a sealed bag, e.g. in the vacuum bag inside a polythene bag or similar. Alternatively, or in addition, most pyrethrins/pyrethroid based space sprays will quickly kill exposed flies and in some situations smoke formulations based on permethrin can be very effective. Special care must be taken to follow label instructions, particularly in view of the fire risk.
Caution. Bats may be living in areas of buildings, such as roof spaces, which are used by cluster flies. Bats are protected (Wildlife and Countryside Act 1981). Care must be taken to survey for signs of bats in cases of doubt and if bats are present the relevant Statutory Nature Conservation Authority must be notified before any insecticidal or other treatments are applied
Housefly and Lesser Housefly
(Musca domestica and Fannia canicularis)
Very common worldwide often in association with human activity. Adults active fliers, highly mobile and capable of travelling several miles. Breed usually in rotting vegetable matter or animal faeces.
Egg – larva – pupa – adult.
Eggs – whitish, 1mm, several batches of up to 150 on rotting materials or animal faeces. Hatch 8 hours to 2 days.
Larvae – legless maggots up to 12mm long in groups on semi-liquid food. 3 moults, usually develop in 1–2 weeks (range 5 days to 1 month or more). Move away from food when fully developed .
Pupae – Inside reddish ovoid puparia in soil or dry area. Develop in 1–2 weeks
Adults – 6mm, greyish with pale stripes on thorax, pale yellow underside of abdomen. Wings spread slightly when at rest. Large red eyes, acute sense of smell.
Disease transmission, spoilage of food, nuisance. May be severe problem in animal units and sometimes refuse tips.
Breeding reduction by covering larval food materials, good hygiene.
Larvicides and biological control in animal units.
Adults by proofing, screening windows, traps. Knockdown pyrethroids. Bait formulations of residual insecticides in animal units.
Distribution and Habitat
The housefly is distributed worldwide, although fairly distinct races have been described from the tropics and the temperate zones, which are capable of inter-breeding but exhibit some individual behavioural characteristics. The housefly is found wherever suitable breeding conditions exist, usually rotting, fermenting or at least moist organic matter, preferably of a high protein content. Houseflies are frequently found in association with humans either indoors or taking advantage of other human activities.
The female common housefly lays fairly large batches, anything up to 150 at one time, of whitish ovoid eggs each approximately 1mm in length. These are deposited on a suitable food medium for the resulting larvae and the rotting or fermenting state of this substrate frequently causes the eggs to hatch quite rapidly – from eight to 48 hours after being laid.
Development of the small white maggots can be quite rapid depending on the quality of the foodstuff. In high-protein value food such as chicken droppings and horse excreta, the entire larval development period may take only five days providing the temperature remains favourably high, from 30 – 40 °C. Under ideal conditions the young larvae will favour the semiliquid part of the food medium; as they pass through the larval stages they will naturally migrate towards the drier areas. After three skin moults the larva reaches about 12mm in length and will have developed a creamy or yellowish white colour. It is distinctly carrot shaped with the rather rudimentary mouthparts at the sharp end.
The mature larva seeks out a drier site in which it can bury itself for pupation. It casts the last larval skin that remains in place, slightly changed in shape to form a fairly smooth ovoid which gradually darkens to a dark brown or even black colouration. The pupa is formed and hidden inside this puparium.
The adult fly emerges some days later, again depending on temperature, forcing its way up through the layers of dryish excreta or other medium by alternately inflating and deflating a sac-like extension to the front of its head. Once fully emerged into the open air where it can expand and dry its shrivelled wings this expanding bag is finally deflated and is then only seen as a horseshoe-shaped crease between and beneath the eyes. Expansion of the crumpled wings, by pumping blood through the veins, is followed by a gradual darkening of the skin to form the true housefly colouration of grey with vertical black stripes on the thorax and pale yellowish or buff-coloured patches on the sides of the abdomen.
Sites such as poultry houses and piggeries often present the housefly with almost perfect breeding conditions throughout the year. Outside, for example on refuse tips, significant breeding is usually restricted to the seven or eight months of spring through to autumn. The adult flies feed on a whole range of liquid food that they can suck up with their sponge-tipped proboscis. Alternatively they may eject saliva onto a solid food material which, when dissolved, can be sucked back up. This process results in drops of vomit being left during feeding and also darker specks, which are an indication of the fly's almost continuous defecation.
Houseflies are known to transmit enteritic diseases and intestinal parasitic worms, and are implicated in the spread of typhoid and cholera. They form an unwelcome intrusion into the domestic scene and are indiscriminate in the types of food material on which they settle and feed.
Larger, and sometimes vast, numbers of flies develop in certain protected environments such as intensive animal housing and on refuse and rubbish tips. In housed livestock units their presence can be extremely upsetting for the animals themselves and may create major staffing problems by producing repulsive working conditions. The vomit and faecal marks referred to above are of great significance in the egg industry, such ’'fly-spotting" causing major quality control problems for egg producers. Large breeding populations in animal units, and on refuse tips, frequently overspill and infest nearby housing, offices and restaurants.
Notices have been served under the Clean Neighbourhoods and Environment Act 2005 where flies from housed livestock units have caused problems for neighbours.
Physical control methods should be the first line of attack against houseflies. By preventing or inhibiting breeding in organic matter, adult emergence will be much reduced. Rubbish tips should be covered after each day's work, and manure heaps may have to be sheeted. Bins of waste material should be covered to prevent access by adults seeking an egg laying site.
Drains and gullies, particularly in and around kitchens, should be cleaned frequently to remove organic material and the windows and doors of all food premises should be proofed with fly screens of approximately 1.5 mm mesh. Electronic fly killers (EFKs) which can attract insects to an electrified grid by the use of an ultraviolet light source are not generally effective against houseflies. While they will kill the occasional housefly they are not particularly attractive to them and they will not cope with large numbers of flies emerging from a favourable breeding site.
Sticky fly papers can be efficient in small areas but are sometimes considered unsightly and will seldom cope with a large infestation.
In cases where no local breeding area can be identified, adults may be flying long distances from infestation sources e.g. refuse tips and animal houses.
For adult control in many situations, conventional knockdown or residual treatments will kill the majority of adult flies, in spite of the development of high resistance levels in a number of housefly populations. In intensive animal units the resistance problem can be exacerbated by the application of residual (photostable) pyrethroids and such treatments are not recommended. (See separate section on fly control in animal units.)
Knockdown space sprays, using natural pyrethrins or non-residual pyrethroid mixtures, can achieve spectacular short-term results against fly problems but in many situations the adults killed are quickly replaced by emergent adults. Attempts to break the flies' life cycle by regular spraying often fail without concurrent attention to breeding areas. Where knockdown pyrethroids are used and label instructions permit, higher concentration products are usually more effective.
Residual insecticides applied to the flies' favoured resting areas will control landing flies in some situations.
Housefly control in animal units
The perfect conditions provided by intensive pig and poultry units allow houseflies to breed throughout the year and to produce a large number of generations. Such conditions increase the ability of housefly populations to develop resistance to a range of insecticides. The use of most standard residual products, particularly residual pyrethroids, will quickly induce resistance.
Control of the physical conditions in fly breeding areas within deep pit and other animal units, together with the encouragement of predatory insects, such as the beetle Ca rcinops pumilio, is of paramount importance. Great care must be taken with the use of conventional insecticides to avoid killing these beneficial insects and conventional residual insecticides should on no account be applied to manure.
Bait or bait spray formulations containing a residual insecticide and an attractant induce the flies to feed and take in more active ingredient. This increases the kill rate and reduces the likelihood that flies will receive only a sub-lethal dose of insecticide and survive to breed.
There are some attractive fly baits available based on imidacloprid and spinosad that can be effective when applied to suspended boards.
A "selective" larvicide, containing cyromazine, is now available which, when applied to the surface of manure or refuse tips, will disrupt the development of early stage fly larvae but have no affect on beetles. Carefully used as part of an integrated pest management system this product can assist successful housefly control even where there is resistance to conventional insecticides. Diflubenzuron can be used in a similar way.
Lesser House Fly
This species is slightly smaller than the common housefly with only three less distinct longitudinal stripes on the grey thorax and yellow basal patches on the abdomen which is otherwise darker grey or black. Most of the biological details of the former species apply broadly to the lesser housefly. Differences include the banana-shape of the eggs and the very distinctive larval shape, where each segment has a number of slightly flattened fleshy extensions. The wings do not have the sharply bent wing vein found in Musca domestica.
As before, a puparium protects and hides the pupa. The adult flies usually emerge in less than a fortnight, mate, and then often separate. Whereas the female tends to stay around the area suitable for oviposition and larval development, the males will frequently migrate considerable distances. Poultry units are favoured breeding sites but even roadside puddles and dykes are sufficient for successful breeding.
Indoors, the Lesser House Fly exhibits a characteristic angular flight with straights of about 20 - 30cm followed by acute turns in the air. Interaction between two lesser houseflies on the wing usually results in a frenzy of close-coupled flying and then instant separation to re-form the angular flight patterns. This species also favours resting on vertical surfaces e.g. cords and chains. These two characteristics will usually distinguish it from the common housefly. Its ability to spread diseases amongst humans seems to be less than that of the common housefly, although this may be more due to its more restricted contact with humans rather than any innate reason.
It may be a pest in certain types of poultry units such as older types of battery houses, semi-free range and deep litter systems but is rarely found in deep pit houses.
Very common outdoors and may come indoors to breed. Several species usually breeding on rotting vegetable matter, fruit, sour milk, beer or vinegar Very rapid breeders (one generation in 7–8 days at 30 °c)
Egg - larva - pupa - adult
Eggs - about 500 eggs per female, approx. 20 per day on suitable food material depending on species
Larvae - small legless maggots, 3 moults, develop in few days. Move to drier area when fully developed.
Pupae - in brownish puparia, develop in only a few days
Adults - 2mm, greyish with large (red) eyes
Potential disease transmission, nuisance. Difficult to remove pupal cases from milk bottles.
Good hygiene, find breeding sites and cover or remove breeding materials Knockdown sprays may be of limited efficacy.
Distribution and Habitat
The famiIy Drosophilidae contains over 50 species of very small to small flies whose primary common feature involves their liking for fermenting material, preferably of a fruit origin. One of todaY's most common species was quite a rarity in Britain in the early 1940s and has subsequentIY become widespread. Other species have been common throughout Britain for as long as records exist. Many species live out of doors and can be found feeding on sap exuding from trees and rotting fruit on the ground. They sometimes come indoors when human activities produce attractive conditions.
The female fruit fly lays a variable number of eggs, averaging perhaps 20–25 per day, and a maximum of 700–800. These are laid on the material that will be the foodstuff for the hatching larvae. The choice of food material varies from species to species. Drosophila funebris F. frequently prefers sour milk and milk products and can be found quite commonly in uncleaned stale milk bottles. Drosophila repleta (Wollaston) is said to favour rotting vegetables and fruit for its larval development. The larvae develop through three skin moults and, when mature, migrate away from the food material to pupate in the nearest convenient soft material, ideally loose soil. The entire life cycle may be completed in and around the rotting material providing a drier area can be found for pupation. The length of time between adult egg laying and the emergence of the next generation of adults is mostly dependent on temperature, and can be as short as seven or eight days at around 30 °C. This may be extended to around 30 to 35 days at 15 °C. When fully grown, at about 8mm in length, the larvae leave the foodstuff and search for undisturbed corners and crevices to pupate. In fact, the final larval skin is used as a puparium and the adults emerge from one to two weeks later to start the new cycle. Under ideal hot summer conditions the entire life cycle can take place in about 12 days but a more average figure would be around a month.
The larvae are quite capable of resisting extremes of temperature and most importantly can survive low temperatures for extended periods; up to six months at around 9 °C has been recorded.
Fruit flies breeding out of doors are seldom of any significance to man. Where infestations develop in pickling or fruit packaging plants or in the refuse areas of kitchens and canteens the clouds of adults are a nuisance. The habit of some species in preferring to feed on faeces and other excrement, prior to settling on clean materials such as food preparation areas, makes them totally unacceptable.
Their breeding rate is particularly high at high temperatures and situations have occurred where the breeding of fruit flies in, for example, bulk stock-piled potatoes in a food manufacturing plant has been so great that no amount of insecticidal head space fogging was sufficient to control the infestation. Such vast clouds of flies can then cause a secondary nuisance by invading nearby housing and offices.
Some species of fruit flies have been valuable to humans as a study material for both simple and complex investigations and experiments in genetics.
Control of fruit flies is best achieved by preventing conditions that are conducive to their development. Where localised infestations occur within buildings seek out suitable breeding materials such as fruit juice, rotting vegetables, fruit and other food materials. High risk produce should be stored under cool and dry conditions to reduce the risk of early fermentation. Drains, gullies and all other sources of food residues should be kept clean by frequent washing down. While space sprays based on pyrethrins or synthetic pyrethroids can knockdown adult flies, the small size of the fly seems to reduce the efficacy of some misting formulations and the sole use of this method is unlikely to give more then temporary relief.
Mosquitoes, Gnats & Midges
(Culicidae, Anopheles spp.)
Very common worldwide. Adult females feed on the blood of humans and other animals. Males harmless. Breed in, usually still, water. Aquatic larvae must come to the surface to breathe air.
Egg – larva – pupa – adult.
Eggs – laid singly or in batches according to species, float on water surface. Hatch in few days.
Larvae – aquatic but breathe air through spiracles. Feed on minute plants, debris. Wriggling movement and will dive to escape danger.
Pupae – also air breathe at surface but can move to escape danger. Adults – up to 10mm, narrow bodied, long legged.
Many species can bite causing irritation. Disease transmission very important in tropics and, though much less likely, potentially so in UK.
Breeding site control in outside areas difficult but Bacillus thuringiensis product is cleared for use in casual water and marshland.
Adults using knockdown products or repellents.
Distribution and Habitat
Anopheles mosquitoes are found worldwide and are particularly significant in the tropics because these are the species that carry malaria, yellow fever and dengue fever. Several Anopheles species occur in Britain and it is thought that the "ague", which was the British version of malaria found in some east coast counties up to the early years of the last century, was transmitted by Anopheles atroparvus . All of the Anopheles have aquatic larvae, although some species prefer salt water, some brackish, and others fresh water. Otherwise their life histories are similar and the characteristic resting position of the adult mosquito is a common feature throughout the genus.
The female mosquito lays single eggs on the surface of a suitable body of water. The boatshaped eggs float horizontally and always remain upright. The young larvae hatch directly into the water and immediately swim with a curling and flicking motion of their bodies. They breathe through a pair of spiracles situated towards the end of the abdomen and remain suspended horizontally beneath the surface film to absorb oxygen. They feed on floating and suspended particles of dead leaves and plant debris and sometimes settle on the leaves of aquatic plants to nibble at the algal growth.
Fully grown larvae, having moulted several times during a period of four to eight weeks, pupate in the water and hang head down from the surface film. When disturbed these pupae, which are shaped like the figure six, can dive immediately by rapid tail paddling. The adult mosquito emerges at the water's surface and stands on the surface film whilst extracting itself from the pupal case.
Male mosquitoes feed on the nectar of flowering plants and therefore do not have the tubular piercing mouth-parts of the female. Their extremely ornate feathery antennae also distinguish them. The female Anopheles mosquito with her relatively long legs holds her body and proboscis in a straight line at an acute angle to the surface on which she is resting. When sucking blood she appears to be standing on her head whilst pushing the tubular sucking proboscis through the skin of the host animal.
There are several Anopheles species in Britain with different habitats: coastal salt water, inland brackish pools and water-filled holes in logs and tree trunks. The females of all species readily bite humans and in some years large numbers develop in coastal areas creating significant public health problems. The adult females attempt to hibernate and frequently come indoors in the late autumn. They may be temporarily roused from their hibernation on mild days and then search for a blood meal. The male mosquitoes live only a short time and are all dead by the onset of winter.
Mosquitoes are opportunistic breeders and even small sources of stagnant water may be used. Covering such potential breeding sites may reduce local problems. Conventional insecticides are not available for the control of mosquito larvae in the UK for environmental reasons. A biological larvicide Bacillus thuringiensis var. israeliensis (Bti) is cleared for use in casual waters and marshland.
Hand-held domestic aerosols are generally effective in knocking-down adult mosquitoes that manage to enter dwelling houses.
Other Mosquitoes, Gnat and Midges
Common gnat (Culex pipiens)
The female Culex lays batches of eggs on the water surface which stick together in raft-like structures. The life cycle is very similar to the Anopheles but the Cu lex larvae differ in having a breathing tube or syphon, which is pushed up through the water surface film whilst breathing. Otherwise, the habits and food requirements are the same as above.
The common gnat is very widely distributed throughout Britain. The adult females hibernate very frequently in houses or outbuildings but most gnat species do not bite and suck mammals and are not a significant problem domestically. One species Culex molestus, which will breed in drains, underground sumps and other areas within or close to buildings, will bite humans. Culex may be distinguished from the Anopheles species by their shorter front legs and the fact that they hold the proboscis and abdomen at a slight angle and more or less parallel to the surface on which they are resting. The Anopheles species have a dark grey or blackish thorax and abdomen; the Culex mosquitoes are mid to dark brown.
This genus of mosquitoes commonly bites mammals, including humans, and there are about 14 different species in Britain. Adults are notable for laying their eggs in damp soil, hollows of trees etc., in places that are likely to subsequently fill with rain. The eggs develop but do not hatch until immersed in water weeks or even months later. The species that commonly bite humans can be divided into two groups according to their habitat.
Species that live in woods include Aedes cantans, A. pu nctor, A. rusticus and A. annulipes. The breeding sites selected range from exclusively shaded pools (A. cantans) ', ponds and ditches partly shaded (A. rusticus, A. punctor) to more open pools on the edge of heaths and woodlands (A. annulipes) . The adults are most troublesome near the breeding grounds and all four species have one generation per year. A. rusticus overwinters in the larval stage but the other three pass most of the winter as eggs.
Species that live in salt marshes include A. detritus and A. caspius and both prefer brackish water (though A. caspius will breed in fresh water). Therefore, it is mostly the coastal regions where these species are most troublesome, though they will attack two to three miles from their breeding grounds. The salt marsh species can produce several generations during the summer months. They commonly breed in stagnant water behind broken and leaky sea walls or ineffective sluice gates that allow incursion of seawater at high tides. Flooded golf bunkers and disused pits near the sea are also good breeding grounds.
Banded Mosquito (Culiseta annu ata)
This species, previously referred to as Theobaldia annulata, is a common species in Britain. It is quite distinctive, being one of the largest mosquitoes, at about 8mm in body length excluding the proboscis and antennae. Its wings are often spotted with dark patches of scales, the abdomen is banded with white and the long black legs are also clearly banded with white. Its biology is similar to the above species, and it frequently hibernates indoors. The females are easily disturbed in hibernation and will then actively search for a further blood meal.
Very common in the vicinity of sewage works where they irritate workers and nearby inhabitants by flying into the eyes, mouth and nostrils. They breed on the fungi, algae, bacteria and sludge that make up the biological layer present on the surface of sewage percolating filter beds. Relatively slow breeding, there may be about 8 generations a year with serious outbreaks associated with emergence of adults in the summer months.