Cluster flies are found throughout the UK, but predominantly in rural areas. Their common name refers to their habit of forming clusters when hibernating, often in large numbers in caravans, holiday homes, the upper rooms and roof spaces of buildings during the autumn period. Whilst there is a specific species of common cluster fly (Polleniarudis), there are four other species which vary in size and colouration, so it is possible to have mixed populations of flies causing the problem inside suitable buildings.
Any of these species of fly presence is not a sign of poor hygiene.
During the summer months, these flies live and breed in fields and are not a problem. They are parasitic on earthworms and their larvae live in the soil, emerging as adults at the end of summer. In the autumn under natural conditions they would hibernate in dry sheltered areas such as under loose bark or in hollow trees. The survivors of the winter would then emerge the following spring to return to the grassy fields to continue their life cycle. However, with houses close to open spaces and fields it is quite common in the autumn for these flies to congregate in large numbers on the outside of buildings, especially on sunny, south-east facing, light-coloured walls. As the afternoon temperatures begin to fall they tend to crawl into crevices for shelter, sometimes through window frames, but mainly under the eaves/fascia boards into the roof space. The following days they may emerge and sun themselves but as autumn moves on and temperatures drop they finally remain inside until the process is reversed the following spring. The big problem is that they tend to invade in large numbers. Fitting fly-screens is of little use against this specie of fly as it prefers to squeeze into small cracks around tiles, window frames etc., hundreds of flies in an enclosed space are a big nuisance. The flies tend to return to the same property year after year. Even if there are similar buildings nearby, they may not be affected. It is not known why one building is preferred, it may be that the flies are attracted to lighter coloured buildings, sunnier spots, or use pheromones to locate old roosts, it is certainly no suggestion that it is due to poor hygiene.
For small infestations, if you do not want to use insecticides, a vacuum cleaner will give limited effect by simply sucking up the flies. Like a fly spray, this will only deal with the flies you see – it will not control any that are hidden and hibernating. Old fashioned fly-papers again give a limited control effect and are not really suited to large scale fly control.
Cluster flies are not damaging to property!
They enter buildings in autumn purely to hibernate over the chilly winter months.
Cluster flies feed on decaying vegetation and earthworms!
This species of fly is not to be associated with dead animal bodies, faeces and the resulting maggots.
There is very little that you can do to stop the flies getting in. Making sure that windows are closed securely and gaps around window frames are sealed. Sealing obvious entry points can offer limited help, but it is not possible to stop a fly getting into a building; and if one fly can get in, so can the hundreds of others.
The good news…
…is that although you may be unfortunate, and have invasions of cluster flies every year, control is easy. Using an ordinary aerosol fly spray in the loft will kill all the cluster flies it hits, but will not penetrate into the cracks where flies may be hibernating. For larger scale control, such as holiday homes, Kendal Caravans offer an economical and practical solution.
The Midi Fumer is an insecticidal smoke generator. One generator placed at either end of the holiday home is an effective way to treat cluster fly infestations.
Contact us on 01539 823 659 to get your midi fumers now!
Alternatively, e-mail service@kendalcaravans.co.uk