Cluster Flies in Spring - PEST UK

Providing pest control services in Berkshire, Buckinghamshire, Essex, Hampshire, Hertfordshire, Kent, London, Middlesex, Northamptonshire, Oxfordshire, Surrey, West Midlands, West Sussex, Wiltshire. Est. 1985.

Cluster Flies in Spring

In Pests

Cluster Flies in Spring

Cluster Flies in Spring are dark grey flies about 8mm long with yellowish hairs on their backs with overlapping wings. In autumn they will congregate in large numbers in upper rooms or roof spaces of houses to hibernate. They then reemerge in Spring to look for egg laying sites outside.  They are sluggish in flight and are a nuisance in the house.

These flies can be found in large numbers in houses, most often lofts, causing annoyance to occupants. They will enter during the Autumn to hibernate and leave in early Spring, sometimes appearing on warm Winter days. It will be at these times they become a nuisance and treatment becomes necessary.
There are 3 types of cluster fly: the most common is parasitic on earthworms, the other 2 are the Autumn Fly, and the Green Cluster Fly, both of these breed in cow dung. All 3 species lead solitary lives except when they gather in the Autumn to hibernate.

Cluster Flies in Spring


We can treat the infested and surrounding areas with a residual insecticide spray such as- Effect Microtech, Permost Uni or K-Othrine. The insecticides we use are the most modern insecticides available. A smoke generator may have been used, this is called Coopex Smoke and contains Permethrin. The type of insecticide used will depend on individual circumstances and be decided by the technician when on site.

All insecticides used are biodegradable, almost odourless, non-tainting and do not corrode or stain. They are not toxic towards mammals but are extremely so to all forms of crawling and flying pests. All the resting places will have been sprayed and possibly dusted.

What Do I Do Afterwards?

After your treatment do not let domestic animals walk on treated surfaces until dry and if bare skin comes into contact while wet then wash. As long as the surfaces that have been treated are not washed down the insecticide will remain active for up to 3 months. This only applies to clean areas inside.


PESTUK are full members of the BPCA, the governing body for pest control in the UK. Using a BPCA member company ensures you have a qualified, fully insured company treating your pest problem.

PESTUK have offices in BalhamOxfordGuildfordEnfield, Potters Bar, Reading,  SheppertonWantage,  SalisburySt Albans, Stevenage and Ware.

Call us on 0330 100 2811 to book an appointment regarding- Cluster Flies in Spring, or any other pest problem you may have.


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