Cluster Flies Facts • Fly Infestations and How To Get Rid Of Flies

Cluster Flies

Are found in numerous locations, but usually in lofts, window frames including sash windows and timber cladding.

Sightings of large numbers of adults in the early or late autumn are the first indication of potential nuisance problems with this insect.

There are three main species of fly collectively known as cluster flies. They are Musca autumalis, a small fly of about the same size and colour as the house fly, Pollenia rudis, a larger fly dull brown/grey in colour, and lastly Dasyhora caynella which is about house fly size and shiny green/blue in colour. Another common cluster fly is the yellow swarming fly this species can congregate in large numbers in attics and disused rooms.

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  • Biology:

    Cluster flies, are very common occurring throughout Great Britain. The adult flies during the summer months, lay their eggs in the earth or in animal dung. Permanent areas of grassland are favourite sites e.g. permanent grazed pasture or parkland as solid cultivation such as ploughing disrupts the flies breeding cycle. The larval stage is parasitic, entering earthworms and feeding upon them until emerging as an adult fly.
    Cluster flies migrate from outdoors into the lofts of houses and farm buildings during the autumn months causing a nuisance to householders. Obvious signs of an infestation is a roof space containing a large quantity of lethargic flies and a quantity of dead flies. Unless the loft is used for storage purposes or is accessed regularly the flies will hibernate successfully leaving in early spring.


    Reasons for control:

    Cluster flies are not damaging to property as they enter buildings in the autumn purely to hibernate over the cold winter months. As mentioned above they feed on decaying vegetation and earthworms. Cluster flies are not to be associated with dead animal or decomposing organic matter. Fibre glass insulation material in lofts can look unsightly if covered with the bodies of flies that have not hibernated successfully although its insulation properties will not be altered and no damage to the roof structure will occur.

    If the loft is home to a hibernating colony of flies, first floor lighting diffusers or sunken spot light diffusers can become full of dead or dying flies. This often occurs in houses where the loft area has been converted into a living room. In most buildings built after 1950, the external roof covering has an under felt layer. Cluster flies can successfully hibernate undetected between these two layers. Often cluster flies can be seen basking on sunny grassland or resting on warm south facing walls of buildings. Cluster flies, like birds, return to roof spaces previously occupied so re-infestation in following years is almost inevitable.


    The best option available is to try and control the number of flies by either:-
    Insecticidal space spray. The number of visits required will depend on the time of year the treatment is carried out and also on weather conditions as to when flies come in to hibernate.

    The use of fly control units also works well (N.B. it is not recommended that electric grid machines are used in loft areas/roof voids, however if you wish to use this type of machine it is important that these are used with an extra deep cluster tray and checked on a regular basis). Please see our online eshop for fly killer units which are suitable for controlling cluster flies.

    N.B. Bats are protected by law it is illegal to kill, or even disturb bats in their roosts. If they are present in the roof space, then it is not recommended that any sort of fly control is used. We will in the first instance not treat cluster flies if we find bats are present.

    It is however worth contacting the Bat Conservation Trust for advice if you are aware you have bats using the loft. They will advise on the best course of action.

    Call Vermatech today to arrange an appointment.

    All works carried out by us will be undertaken by fully qualified, professional technicians trained to RSPH Level 2 or equivalent.

    Think you have a cluster flies problem?

    Common Insects and Rodents

    Below are a list of some of the more typical rodents and insects we provide pest control for.

    Rats icon


    There are two species of rat in Britain, Rattus Norvegicus which is commonly known as the Brown Rat or Common Rat. The Rattus Rattus, referred to as the Black Rat or Ship Rat is now rarely found in the UK.

    Mice icon


    The House Mouse, and sometimes the Long-Tailed Field Mouse are found in buildings as they seek the warmth and shelter for nesting sites and food.


    Grey Squirrels

    Deliberately introduced to this country sometime in the 19th century, the grey squirrel has spread throughout most of mainland England & Wales. Mainly a resident of broadleaved and mixed woodlands it is also a typical resident of urban parks and gardens.

    Cockroach icon


    Cockroaches are distinguished by their very long whip-like antennae, flat oval bodies and rapid, jerky walk. There are two main species of cockroach in Britain the German and Oriental Cockroaches.

    Fleas icon


    The most common species of Flea is the Cat Flea, known for readily biting humans. The Bird Flea are next in importance, followed by dog fleas, although other species may become temporarily attached to dogs.

    Wasps icon

    Wasps & Hornets

    If you are seeing a large number of wasps or hornets in and around your home or work, there’s probably a wasps’ nest or a attractant nearby.

    Flies icon

    Cluster Flies

    Are found in numerous locations during Autumn to Spring, but usually in lofts, window frames including sash windows and timber cladding.

    Ants icon


    The commonest species of ant that invades houses is the Black Garden Ant (Lasius niger). Black garden ants are not vectors of disease, however they can become a nuisance by way of their foraging behaviour.

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