Pest Control
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Every house gets the odd fly through an open window in summer. Swatting them is fine. When the numbers keep rising, or a room fills with bluebottles overnight, the flies are breeding somewhere nearby, and the answer is to find that place rather than chase the adults.
Which flies come indoors?
The common ones in UK homes are:
- House flies. Grey, about 6 to 7mm, with dark stripes on the thorax. Fast and restless, mostly seen in the warmer months.
- Bluebottles and greenbottles. Larger, noisy blow flies with a metallic blue or green body. They breed in meat and dead animals.
- Fruit flies. Tiny, with red eyes, hovering around fruit bowls, compost caddies and recycling.
- Drain flies. Small, furry, moth-like flies around sinks and plugholes. See our guide to drain flies.
- Cluster flies. Slow, dark flies that gather in lofts and at windows in autumn and winter. They are a different problem with a different answer, covered in our guide to house flies and cluster flies.
Why flies are a hygiene risk
House flies and blow flies lay their eggs in decaying material: food waste, rubbish, animal droppings and carcasses. The adults visit the same places to feed. Because they can only take in liquid, they soften solid food with saliva and digestive fluid before drinking it, and they leave droppings as they go.
That means a fly that has been on a bin or a dead animal can carry bacteria on its feet, body and mouthparts straight onto your worktop or food. Flies are known to spread bacteria such as E. coli and salmonella this way. They are also an important part of nature, breaking down waste and feeding birds and spiders, but they do not belong in a kitchen.
Why the numbers rise so quickly
A female house fly lays her eggs in batches of around a hundred, and can lay several batches in a life of a few weeks. In warm weather, eggs can hatch into maggots within a day and become adult flies in little more than a week. A bin that was not emptied, or a forgotten bag of food waste, can produce a lot of flies very quickly.
A sudden swarm of bluebottles
If a room fills with bluebottles over a day or two, especially in a room nobody uses much, the most likely cause is a dead animal nearby: a mouse or rat under the floorboards or in a wall void, or a bird in a chimney or loft. The flies have bred in the carcass and are emerging into the room. Killing the adults will not stop more emerging until the source is found and removed.
What you can do
- Deal with waste. Empty kitchen bins and food caddies often, keep lids closed, rinse recycling, and keep outside bins clean, lidded and away from doors.
- Cover food. Do not leave food or dirty dishes out, wipe surfaces after cooking and clear spills promptly.
- Pick up after pets. Dog mess in the garden and an unchanged litter tray both breed flies.
- Clean the drains. Grease and food in kitchen drains and gullies attract flies to breed.
- Fit fly screens. Screens on windows and doors you keep open in summer stop most flies reaching the house.
- Use traps for the stragglers. Fly papers, swatters and small light traps are fine for the odd fly. Sprays should be used sparingly and never near uncovered food.
When to call us
Call us if flies keep coming despite good housekeeping, if you have a sudden swarm and cannot find the cause, or if you suspect a dead animal under the floor or in the loft. We find the breeding site, deal with it and treat as needed, and we can advise on screens and fly control units. See our fly control page for how we work.