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Dealing with Cluster Flies

Cluster flies are similar in size to the house fly, common throughout the UK and are known as such due to their habit of forming large clusters when looking for places to hibernate.

During the warmer weather, typically summer and early autumn, Cluster flies will be outdoors but as the weather becomes cooler, they search for shelter and this may take the form of lofts, attics and roof spaces or other sheltered parts in buildings.

The flies will come out and fly around if the weather warms up and as they are attracted to light, will often find their way into the human living space which although unsightly or unpleasant, is not considered to pose health risks to humans as they do not carry or transmit disease, however, make sure any water tanks in loft areas are covered.

Cluster flies have nothing to do with dead carcasses or maggots and poor hygiene does not play a part in cluster flies frequenting a property.

Control of Cluster flies can take several forms:


Always better than cure, if possible, preventing entry is an excellent method of controlling cluster flies, block holes & small gaps around door and window frames, missing bricks or mortar, air ventilation bricks can be covered using Mouse Mesh, this will allow air through but will stop the passage of insects & rodents.

However access to all the areas they frequent may not prove possible and so this is not a method that can always be employed.

Once the flies are in, they can be dealt with in several ways:

Electric Fly Killers

The flies are drawn to the device by ultraviolet light and are then killed either by an electric grid or by becoming stuck to a glue board. If the area is not visited regularly, a glue board type fly killer can provide the safest option as there is no electric grid, removing the danger (slight as it is) of sparks or arcing if the unit becomes swamped with thousands of dead fly bodies.

The Fusion range of fly killers can prove a good choice as they feature large, double sided glue boards. If an electric grid machine is preferred, then using an extra deep Cluster Fly collection tray is recommended.

If there is no electrical supply nearby or the budget won't stretch, then a cheaper alternative can be found by using a Fly Stick or Sticky Fly Papers, both prove very effective against cluster flies.


Whilst conventional aerosol sprays may be used on small groups of Cluster flies, often the sheer number is too great and so using an insecticide such as the Insecto Pro Formula Insect Fogger becomes a more suitable alternative. This is simply activated and the area vacated making it much easier to deal with large amounts of insects in one go. After two hours, re-enter the area and simply vacuum up the dead bodies.

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