Flies

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Last revised: 22 November 2007

A Picture of a Fly

Every year, the Environmental Health Services receives many complaints about fly infestations, particularly during the summer and autumn months. Flies are common in rural areas where there are poultry farms, stables and piggeries, providing an abundant supply of manure in which they can breed. This makes the tracing of a course of a particular infestation very difficult and time consuming. Flies breed in specific areas according to type. This leaflet has been produced to provide information and advice to those people troubled by fly infestations and to serve as an aid to identification. There are many types of fly but the following are the most common cause of problems:

  1. Common House Fly (Musca domestica)

  2. Lesser House Fly (Fannia canicularis)

  3. Autumn Fly (Musca autumnalis)

  4. Cluster Fly (Pollenia rudis)

The Common House Fly

The female house fly can lay 120-150 eggs at a time and, depending on the temperature, the eggs can hatch into maggots within 8-48 hours. The maggots then burrow into a food source. The new fly can emerge any time from four days in the summer months, to several weeks in the cooler weather. In this country, the earliest flies tend to emerge in May and the greatest numbers are usually found during August and September.

Breeding more or less ceases in October, except in heated premises. During the winter, the House Fly's cycle is longer. The flies will breed in suitable indoor places and in decaying animal or vegetable matter, including rubbish heaps and horse manure.

Control

The Common House Fly is best controlled by taking preventative measures at source. Dustbins should be kept clean and all perishable food should be wrapped up. Once flies are in the house, fly papers, although unsightly, are effective, as are some of the 'knock down' sprays.

The Lesser House Fly

The Lesser House Fly has a similar life cycle to that of the Common House Fly, although it does not tend to move between waste matter and human food. It was once common in chicken manure but less so today. It is identifiable by its quick darting movements.

Control

As with the House Fly, control measures should be taken at source. Rubbish tips should be managed properly and any adult flies that emerge can be controlled by daily spraying.

The Cluster Fly

This fly gets its name from its habit of clustering like a swarm of bees. It is larger than the Common House Fly and can be easily identified as it folds its wings over its back.

The Cluster Fly enters a house during autumn to hibernate and leaves again in spring, often causing a nuisance at these times. In the autumn, the flies tend to collect on the outside of buildings on warm elevations and later find their way inside to cluster - sometimes in their thousands - in roof spaces, under tiles and in sash windows.

One building in a row, no different from the rest, may be heavily infested and its neighbour completely unaffected. The Cluster Fly is a parasite of earthworms, which are usually readily available in any domestic garden.

Control

To kill the occasional fly, a 'knock down' spray can be effective. When flies are particularly troublesome, fly strips can be hung up in the roof spaces and any dead flies can be cleared up using a vacuum cleaner. Food should be kept covered at all times to prevent contamination.

The Autumn Fly

The Autumn Fly is similar in appearance to the House Fly. Its name originates from the fact that it only appears in houses during the autumn months. This fly breeds in cowpats, in rural areas, where they are in plentiful supply.

Control

Control measures are the same as those for the Cluster Fly.

The Council does not treat for flies and for professional treatment you should approach an independent pest control company, details of which can be found in local telephone directories and Yellow Pages.