Last updated: July 2025
Noticing strange buzzing noises in your attic? You might have cluster flies — and no, they’re not just regular houseflies. These uninvited guests love sneaking into warm spaces just before winter hits. They hide in attics, walls, and even behind light fixtures, sometimes in huge numbers.
If you’re swatting at slow-moving flies near your windows or wondering where that buzzing is coming from, you’re likely dealing with a cluster fly problem. Here, we’ll walk you through how to get rid of cluster flies step by step — and how to keep them out for good. We’ll show you simple, safe, and effective ways to eliminate them. More importantly, how to prevent them from returning next season.
What Are Cluster Flies and Why Are They in Edmonton?
The name says it all. Cluster flies love to gather in large groups, especially in cozy, undisturbed spaces like attics, wall voids, and under insulation. You might spot them on sunny days, clustering near windows, trying to warm up.
Cluster flies are slow-moving pests often mistaken for house flies but are slightly larger and have golden hairs. In Edmonton, they become a common nuisance during spring and fall as they seek warm spots to hibernate.
They don’t breed indoors or spread disease. But you can’t ignore them as they gather in large numbers. Their return every year is triggered by seasonal temperature changes, especially after a mild fall.
Their tendency to group in the dark corners of your home gives them their name. It makes them a pain to deal with if you don’t catch them early.
Cluster Fly Vs House Fly
Although both insects share similar appearances, cluster flies’ physical traits differ from those of houseflies.
| Feature | Cluster Fly | House Fly |
| Size | Slightly larger (8–10 mm) | Smaller (6–7 mm) |
| Colour | Dark grey with golden hairs | Grey or black with no golden hairs |
| Behaviour | Slow-moving, sluggish | Quick, erratic flight |
| Wings | Overlap when at rest | Slightly spread apart when resting |
| Seasonal Appearance | Fall and Spring (hibernate in homes) | Year-round indoors, especially in warmer months |
| Habitat | Attics, walls, sunny windows | Kitchens, garbage bins, and animal waste |
| Breeding | Outdoors, in the soil near earthworms | Indoors, on rotting food or waste |
| Odour When Crushed | Sweet, sickly smell | Normal fly smell |
| Health Risks | Minimal; no disease transmission | Can spread bacteria and foodborne illnesses |
| Infestation Pattern | Found in large groups (“clusters”) | Seen singly or in small numbers |
Why They Appear in Spring and Fall in Edmonton
Here in Edmonton, cluster flies are most active during spring and fall. In the fall, they sneak into homes to find a warm place to hibernate. Once inside, they tuck themselves away until the weather warms up.
Then spring hits—and bam! They will fly around in front of your eyes, trying to escape back outdoors. They often gather around windows and light fixtures, looking for a way out.
They don’t breed indoors. Unfortunately, if your home was once a comfy winter hideout, they’ll return year after year unless you take steps to stop them.
You can also read: Fleas and Fly Removal Edmonton
Are Cluster Flies Harmful to Humans or Homes
At first glance, cluster flies do not seem like a big deal. They’re slow, quiet, and not aggressive. But just because they don’t bite or sting doesn’t mean you should ignore them. Let’s break down what you need to know.
Health Risks – Should You Be Concerned?
The good news? Cluster flies don’t bite, sting, or spread diseases the way houseflies or other pests might. They’re more of a nuisance than a threat.
That said, if you have a significant infestation, the number of flies can trigger allergies or worsen asthma in sensitive individuals. And let’s be honest, no one wants dozens of flies buzzing around their home in any situation.
Also, dead cluster flies can attract secondary pests like carpet beetles or mites. So while they’re not directly harmful, when you ignore them, they will cause problems.
Do Cluster Flies Lay Eggs Indoors?
Nope. Cluster flies do not breed inside your home. That’s a relief for many Edmonton homeowners. Instead, they lay their eggs outside in soil, typically near earthworms (their favourite larval hosts).
So if you’re seeing flies now, they’re likely leftovers from the fall who’ve been hibernating behind your walls. You’re not dealing with a growing problem, just a hidden one.
Why You Shouldn’t Ignore a Sudden Infestation
If you suddenly notice a bunch of flies appearing around your windows, it’s not random. It usually means a larger cluster is waking up behind the scenes.
So, do not ignore them for these reasons:
- The smell of dead flies can attract other pests.
- They may return every year if you don’t seal off entry points.
- And let’s face it—living with buzzing bugs indoors isn’t peaceful.
- Catching the problem early means fewer flies, less cleanup, and no unwanted surprises come next season.
How to Get Rid of Cluster Flies Naturally
You don’t have to use harsh chemicals to get rid of cluster flies. There are natural ways to keep them out of your home. And yes, many of them work surprisingly well, mainly when used consistently.
What Smells Do Cluster Flies Hate?
Cluster flies have sensitive noses and can’t stand strong, pungent scents. Here are a few that drive them away:
- Eucalyptus oil – Acts as a powerful fly repellent. Add a few drops to cotton balls and place them near windows.
- Peppermint oil—Flies hate the fresh, minty smell of this oil. Mix it with water and spray around doors and sills.
- Citronella – Known for repelling mosquitoes, citronella also helps deter flies.
- Vinegar traps – A shallow dish of apple cider vinegar with a few drops of dish soap. Flies get lured in and can’t escape.
How to Eliminate Cluster Flies DIY
You don’t always need heavy chemicals to deal with cluster flies. A few practical, easy fixes around the house can make a big difference:
- Seal small gaps or cracks around windows, baseboards, and attic vents, as these are common entry points.
- Tuck herbal sachets with bay leaves, cloves, or dried lavender into warm corners—flies hate the smell.
- Set up UV light traps in quiet spots to catch flies without using sprays.
- Vacuum regularly—especially window sills, attics, and crawlspaces where flies like to hang out.
Pros and Cons of Natural Methods in Alberta’s Climate
Natural remedies are a helpful first step. However, for recurring problems, professional help might still be the smarter option.
| Pros | Cons |
| Safe for children, pets, and the environment. | Less adequate for severe or large infestations. |
| Budget-friendly and easy to DIY. | Oils and scents fade quickly in dry or drafty indoor areas. |
| No need for harsh chemicals or pesticides. | Outdoor treatments are limited during cold Alberta winters. |
| Reduces chemical exposure inside the home. | Requires consistent reapplication to maintain effectiveness. |
How to Stop Cluster Flies from Returning
Seal all entry points: Use caulk or weatherproof sealant to close gaps around windows, doors, vents, and attic eaves. Focus on south- and west-facing walls where flies tend to gather.
Install or repair screens: Ensure all windows, soffits, and vents are covered with fine mesh screens. Replace or patch any tears to block fly entry.
Use UV fly lights or traps: In spring, place light traps in attics, basements, and near windows to catch flies trying to get outside.
Insulate and air-seal your attic: Cluster flies love undisturbed, warm spaces. Improving insulation and airflow can make your attic less inviting.
Vacuum and clean fly-prone areas: Regularly clean window sills, attic corners, and crawl spaces where cluster flies tend to hide.
Use essential oil repellents: Apply eucalyptus, peppermint, or citronella oil around suspected entry points to discourage re-entry.
Inspect annually in late summer: Early fall is prime time for cluster flies to sneak in. To stay ahead, do a quick inspection each August.
How To Get Rid of Cluster Flies Outdoors
It will be your most brilliant move if you can stop cluster flies outside before they get inside. Making small changes around your yard and exterior is a brilliant idea.
- Inspect the exterior of your home for tiny cracks, gaps, or holes. Check around siding, vents, and rooflines.
- Apply outdoor caulking or weatherstripping to seal openings.
- Keep exterior lights off at night when not needed.
- Install fly screens or mesh over wall vents and attic openings.
- Keep your yard well-trimmed, mainly grass and bushes near the home’s foundation.
- Avoid storing organic compost or decaying vegetation near the house.
- Rake up fallen leaves in the fall; they attract insects, including cluster fly larvae.
- Ensure drainage is good to avoid moist soil, which supports earthworms (the flies’ breeding host).
- Reapply natural options like neem or essential oil sprays, which are eco-friendly and safe.
- Chemical treatments (like residual insecticides) are stronger and longer-lasting but should be applied by professionals.
What If DIY Fails? Professional Pest Control in Edmonton
Sometimes, despite your best efforts, the flies return. That’s where the pros step in.
If you notice:
- Flies are coming back year after year
- Swarms near windows or attic spaces
- DIY methods not working after 1–2 weeks
…it’s time to bring in help. A professional can
- Assess hidden entry points
- Locate fly clusters behind walls, and
- Safely eliminate them without damaging your home.
Why Choose Major Pest Control in Edmonton?
We know Edmonton’s seasonal pest patterns inside and out. All of our services are eco-conscious and child/pet safe. We always offer fast response, no-pressure quotes, and long-term solutions, not just temporary fixes.
FAQs
What’s the difference between a cluster fly and a house fly?
Cluster flies are slightly larger, move more slowly, and have golden hairs on their body. House flies are smaller, faster, and don’t have those golden hairs. You’ll often see cluster flies buzzing lazily near windows in the fall, while house flies are active year-round and more commonly found around food and garbage.
Why are cluster flies showing up in my attic?
Cluster flies sneak into attics and wall voids to hibernate during the fall and winter. They’re looking for warmth and shelter, not food. If your attic isn’t sealed correctly, it becomes the perfect hideout.
Are cluster flies harmful to humans or pets?
Not really. Cluster flies don’t bite, sting, or spread diseases like house flies do. But they’re annoying, especially when they show up in large numbers and start buzzing around inside.
Do cluster flies infest the same way as house flies?
No. House flies breed in rotting food or waste that is left indoors. Cluster flies lay eggs outdoors, and their larvae develop inside the bodies of earthworms. They only come indoors to hibernate, not to reproduce.
How do I get rid of cluster flies in my home?
Seal up cracks and gaps before fall. Vacuum up any flies you see, and consider a pest control service if they’re swarming. Treating your attic or walls in late summer can stop them from getting in.
Do cluster flies return every year?
Yes. If your home was cozy once, they’ll come back. Preventive sealing and treatment are essential to breaking the cycle.
Can cluster flies damage my property?
They don’t chew or nest, but large infestations can attract other pests and leave unpleasant odours and messes behind.
Is it safe to vacuum them up?
Yes. Vacuuming is a great way to get rid of visible flies. Just be sure to empty the canister immediately to avoid odours.
Conclusion
Say Goodbye to Cluster Flies for Good – Naturally and Professionally
Whether you’re going the natural route or calling in experts, the key is early action and long-term prevention. Don’t let cluster flies turn your home into their seasonal getaway. Seal up, clean up, and team up with trusted pros like Major Pest Control Edmonton to keep your space pest-free year-round.
You can read: Environmental Protection Agency – Integrated Pest Management (IPM) Principles