Quick facts
- Common types
- House fly, bluebottle, fruit fly, drain fly and cluster fly
- House fly
- About 6 to 7 mm, grey with four dark stripes on the back
- Fruit fly
- About 2 to 3 mm, tan-brown, drawn to ripe fruit and fermenting liquid
- Cluster fly
- Slightly bigger than a house fly, slow, with golden hairs; gathers in lofts in autumn
- Breeding
- Rotting food, bins, drains, dead animals and damp organic material
How to identify flies
Different flies point to different problems. House flies are drawn to bins, food waste and pet waste. Bluebottles and greenbottles often indicate something dead, such as a trapped rodent or bird in a wall, chimney or loft. Fruit flies breed in overripe fruit, fermenting drinks and damp drains. Drain flies (moth flies) come from slime in drains and sinks. Cluster flies shelter in lofts and wall voids in autumn and emerge on warm winter days.
A sudden spike in flies indoors, particularly large bluebottles in a loft or upstairs room, can mean a dead animal. Your technician can help locate it.
Signs of flies in your home
- Large numbers of flies in one room or window
- Maggots in bins or waste, or in hidden places
- Fruit flies around fruit bowls, bins and drains
- Clusters of dozy flies in lofts or bedrooms in autumn
- A sweet, rotting smell in a wall or ceiling void
Risks and damage
Flies can carry bacteria from waste to food and surfaces, which makes them a hygiene issue in kitchens, restaurants and care settings. Large numbers are distressing, and flies indoors in winter often signal a hidden problem.
Why flies come into properties
Waste, drains, rotting food and a source of moisture. Open windows, doors and gaps let them in, and a dead animal within the building can lead to a sudden infestation.
How to prevent flies
- Use lidded bins, wash them regularly and keep food waste sealed
- Clean drains, sink overflows and floor drains to remove the slime flies breed in
- Store fruit in the fridge and clear spilled drinks and compost promptly
- Fit fly screens to windows and seal gaps
- Remove dead animals promptly and check lofts and voids
Professional fly control by Southwark Pests
The most effective control is to find and remove the breeding source. A professional will identify the species, treat the source, apply residual treatments to resting areas and may use fly units in commercial kitchens. Insecticides alone do not solve the problem if the breeding site remains.
When to call a professional
Call a professional if you have large numbers of flies, if you suspect a dead animal in the building, if cluster flies return every autumn, or if you run a food business.
Fly control across Southwark and London
Fly problems in South London often start with bin stores, blocked drains or a rodent that has died under the floor. In food businesses, flies can affect your food hygiene rating. We cover South London, Central London (the City, the West End and Westminster), East London out to Stratford and Newham, and nearby parts of Kent, from our base at South Dock Marina in SE16. A standard visit is £90, and you can book online or call 020 8050 2022.
- Southwark
- Bermondsey
- Peckham
- Camberwell
- Rotherhithe
- Lambeth
- Brixton
- Lewisham
- Greenwich
- Bromley
- Bexley
- Kent
- Central London
- City of London
- Westminster
- East London
- Tower Hamlets
- Hackney
- Newham
- All areas
Fly control: questions and answers
Why do I suddenly have lots of flies indoors?
Look for a breeding source such as a bin, drain, rotting food or a dead animal. A sudden surge of large flies often points to something dead in a wall or loft.
How do I get rid of fruit flies?
Remove ripe fruit and fermenting liquids, clean drains and bins, and trap adults with a vinegar and washing-up liquid trap. Persistent cases need professional help.
What are cluster flies?
Slow, hairy flies that overwinter in lofts and wall voids in groups, then emerge on warm days.
Do flies bite?
House flies do not, but some species, such as stable flies, can. Most indoor flies are a nuisance rather than a bite risk.
Can flies spread disease?
They can carry bacteria on their feet and mouthparts, so food hygiene matters.
Are fly sprays effective?
They knock down the flies you can see but do nothing about the source.
Related pages
This page is general information, last reviewed on 19 October 2026. It is not a substitute for an on-site inspection.