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Flies

Environmental Health

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Flies

The scientific name for flies, Diptera means two wings. There are thousands of different species but all follow a complete metamorphosis with distinct egg, larval, pupal and adult species.


Common Housefly (Musca domestica)

Adults, 6 - 8mm long with 13 - 15mm wingspan; gray thorax with 4 longitudinal dark stripes; basal half of abdomen buff-coloured and occasionally transparent at sides, with central dark band broadening to cover last abdominal segments; at rest, the wings are spread.

Houseflies can transmit intestinal worms, or their eggs, and are potential vectors of diseases such as dysentery, gastroenteritis, typhoid, cholera and tuberculosis. They will frequent and feed indiscriminately on any liquefiable solid food, which may equally be moist, putrefying material or food stored for human consumption.

Flies liquefy food by regurgitating digestive juices and their stomach contents on to the food substance. This "liquid" is then drawn up by the suctorial mouthparts and in so doing the insects pick up pathogenic organisms, which may collect on their bodies to be transferred on contact with other surfaces or survive passage through the gut to be deposited as fly spots.

 

Bluebottles

Bluebottles are 11mm long and quite distinctive with their deep metallic blue colour. They primarily breed on dead and decaying animal matter. The adults are active fliers and can travel several miles. They will readily enter buildings to find breeding sites.  

 

Control of houseflies and bluebottles

Physical control methods should be the first line of defence. By preventing or inhibiting breeding in organic matter adult emergence will be much reduced. Because of the way flies feed and where they are likely to have come from before settling on the food, it is as well to make sure that you cover any food to avoid contamination.

You should frequently clean drains, particularly near kitchens, and cover your waste bins to avoid providing ideal breeding conditions.

The best ways of controlling or avoiding infestations are good hygiene and taking the simple precautions mentioned above.

Insecticidal control using fly sprays ("knock down" sprays) are a good, almost instant, way of dealing with the problem. Flypapers, while unsightly, are another solution.

Electric ultra-violet fly killers are another means of controlling flies, but their efficiency can be affected by where they are placed

 

Cluster flies

Cluster flies are found commonly throughout Europe and the UK. The common name refers to their habit of clustering and hibernating in numbers in buildings.

The adult female lays eggs on and around damp soil beneath dead and rotting leaves etc.

The life cycle of a fly is very dependent on weather conditions. In Britain it seems that two generations per year are common, but in hot summers up to four generations per year are possible.

During the summer and early autumn these flies are of no consequence. As temperatures drop they search for shelter and frequently form vast clustering masses in roof spaces and lofts, with several thousand flies clustered together. Often a single house or building in a row of similar buildings will be chosen year after year

 

Control of cluster flies

It is often not possible to keep flies from entering premises and it is recognised that while they are a great nuisance on occasion, they are unlikely to represent a health risk. They do not breed indoors and are not indicative of poor hygiene.

Once flies are inside, for example a loft or attic, control methods are relatively simple with physical methods and a range of insecticides and formulations.

Occasionally, a vacuum cleaner (nozzle type) can be used as a sole control method and the collected flies can be disposed of in a sealed bag i.e., a vacuum bag inside a polythene bag. Dichlorvos strips may have some value in killing flies in well sealed loft spaces.