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Cluster Fly Infestation

Cluster Fly Control & Removal

Call your London Fly Exterminators on 0203 600 0351

cluster fly


The cluster flies are unlike blowflies such as the bluebottle/greenbottle, they do not present a health hazard because they do not lay eggs in human food as bluebottles/greenbottles. However, these flies are a nuisance because when the adults emerge in the late summer/autumn they enter houses to hibernate, often in large numbers; they are difficult to eradicate because they infest areas such as roof spaces and wall cavities. They are often seen on windows of rooms that are not used regularly.

Size, Shape and Colour

6-7mm long with a wing span of around 10mm, a relatively big fly, with large reddish compound eyes, yellow hairs cover the thorax with irregular light and dark grey areas on the abdomen.


Eggs distributed favourably in leaf litter or damp soil, the larvae will hatch after a week and try to find earthworms, they then proceed to bore into the body to complete growth to full size then will work its way out to pupate in the soil. Depending on the weather 2-4 generations are possible each year. The flies will hatch from the pupae and contently live outdoors, they will only enter buildings when temperatures start to fall. This happens in large numbers between September and November.

Preferred Foods

The earthworm is an important food source to growth, but only to the larvae. The adult fly could be found feeding on nectar from flowers.


Buildings favoured are south-west and south facing. They will enter buildings via small gaps or building fabric defects gaining entry to roof spaces, voids, cladded walls and even silos. They will cluster on the exterior of buildings in vast numbers then proceed to crawl into gaps. They will start to leave buildings in huge numbers in the warmth of spring.

Pest control treatment for CLUSTER FLIES - Call 0203 600 0351

As with most of our pest control treatments, we usually do two visits as a follow up visit allows us to make sure any actions we take are successful. Our fully trained pest control technician starts by talking to you about the problems you are having before assessing the situation.  Please be aware that the pest controller will often need to inspect other areas and not just the visible source.

Residual insecticides, usually sprays and a ULV fogging are the normal treatment for Cluster Flies. In houses we normally need to treat the loft and the infested areas where the flies may have originally found their way in.

As with all our treatments, the pest control technician will leave a report with you with details of any treatments and recommendations.  If a follow up visit is likely to be needed, our technician will arrange a suitable date and time with you. Generally this will be about a week or two later and sometimes a second treatment is required.
We are a leading pest control company working in and around the Hertfordshire area, using the latest techniques to ensure your pest problems are completely eradicated.
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