As the cooler autumn weather settles in and leaves start to fall, you might notice an unwelcome pattern: sluggish flies gathering in your loft, around window frames, or buzzing aimlessly in upstairs rooms. If this sounds familiar, you’re not alone it’s the time of year when cluster flies begin to make themselves known.
What Are Cluster Flies?
Cluster flies (Pollenia rudis) aren’t your typical houseflies. They don’t breed in bins or feed on food waste. Instead, they spend spring and summer living quietly outdoors, laying their eggs in soil. But as soon as the temperature drops and daylight shortens, they start looking for somewhere warm and sheltered to hibernate, often choosing your loft, roof space, or wall cavities.
They get their name from their behaviour: they cluster together in large numbers, often unnoticed until one mild autumn day when they start appearing en masse around windows, skylights or attic spaces.
Where You’ll Find Them
- Inside lofts, attics, roof voids, and unused rooms
- Around window frames, especially south-facing ones
- In wall cavities, behind light fittings, or tucked under eaves
- Occasionally dropping down into bedrooms or living rooms from above
You may also find dead or dying flies collecting in corners or on windowsills, especially when they’ve been disturbed by indoor heating or unseasonably mild weather.
Are They Dangerous?
Cluster flies are not harmful in the way that house flies can be. They don’t spread disease or breed indoors. But that doesn’t mean they’re welcome.
They can:
- Leave dark staining on walls or ceilings
- Emit an unpleasant, sickly odour
- Reappear year after year in greater numbers
- Become distressing when found in large groups
And if you try to swat or squash them? You’ll often end up with a stained wall or windowsill for your efforts.
Can You Deal with Them Yourself?
There are a few home remedies you can try to manage a small cluster fly issue:
- Vacuum regularly in lofts and around windows to remove dead flies
- Seal cracks and gaps in roof tiles, air bricks, and around window frames
- Use fly screens to stop them entering living spaces
- Install UV fly units in problem areas to reduce numbers
- Use fly traps or sticky strips (although these may not be effective in large loft spaces)
For a mild issue, these methods might be enough to keep things under control. But once cluster flies establish your property as their winter base, they’ll likely return the next year in larger numbers.
When It’s Time to Call in the Experts
If you’re finding dozens (or hundreds) of flies in your loft or window spaces, it’s best to call in professional help. We use specialist treatments designed for exactly this situation.
We can:
- Safely treat lofts, wall voids and other harbourage areas using fogging or ULV (ultra-low volume) techniques
- Provide advice on proofing and long-term prevention
- Offer discreet, fast service tailored to your property
Cluster flies may be a seasonal nuisance, but left untreated, they’ll keep coming back year after year.
Autumn is a wonderful time of year, but it’s also when pests like cluster flies start looking for their winter home. If you’ve noticed signs of cluster flies and aren’t sure what to do, call us on 0800 592011. Or get in touch online for advice, inspections, and effective treatment options.
