---
title: "How To Get Rid Of Cluster Flies In House"
canonical: "https://gadgetguides.org/how-to-get-rid-of-cluster-flies-in-house/"
author: "Arian"
published: "2026-09-10T16:02:57+00:00"
modified: "2026-09-10T16:02:57+00:00"
language: "en-US"
site: "Gadget Guides"
description: "There's nothing quite like the frustration of spotting a sluggish fly buzzing around your living room in the dead of winter. If you're searching for how…"
categories: "Help Guide"
attribution: "Gadget Guides (https://gadgetguides.org/)"
---

# How To Get Rid Of Cluster Flies In House

There's nothing quite like the frustration of spotting a sluggish fly buzzing around your living room in the dead of winter. If you're searching for how to get rid of cluster flies in house, you've probably noticed they're not your typical house flies. They're bigger, slower, and they seem to appear out of nowhere, especially on warm winter days.

 

Per the University of Minnesota Extension, these are overwintering pests that measure about 8 to 10 millimeters long, slightly larger than the common house fly. They don't breed indoors, which is actually good news. It means you can stop them.

 

But you need a different strategy than the one you'd use for summer flies, and that's what we're going to walk through.

 

![How To Get Rid Of Cluster Flies In House](https://gadgetguides.org/wp-content/uploads/2026/09/how-to-get-rid-of-cluster-flies-in-house-mtvpuowy.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

## Quick Answer: What Actually Works and What's a Waste of Money

 

Vacuum them up immediately. Seal all exterior cracks and gaps. Treat attic voids with insecticide dust.

 

The real solution starts in late summer before they arrive. You can stop a cluster fly infestation, but you have to attack the problem at the source.

 

Let's be direct about what works and what doesn't. This is based on our research of university extension guidelines and verified pest control recommendations.

 

**What actually works:**

 

- **Vacuuming**, The best immediate solution. Use a vacuum with a hose attachment to suck up visible flies. Empty the bag or canister into a sealed plastic bag and dispose of it outside immediately.
- **Exterior sealing**, Caulk and expanding foam applied to cracks and gaps in late summer. This is the only long-term solution.
- **Insecticide dust**, Deltamethrin dust applied to attic eaves and wall voids through small access holes. It stays active for months in dry spaces.
- **Professional exclusion**, A licensed exterminator can inspect and seal your home thoroughly, especially useful for hard-to-reach areas.

 

**What wastes your money:**

 

- **Fly paper**, Won't catch enough to matter.
- **Bug zappers**, Attract more flies from outside.
- **Aerosol foggers**, Kill only the flies you see. The rest stay hidden.
- **Scented repellents**, No evidence they work for cluster flies.
- **Window traps**, Better than nothing, but they treat the symptom, not the cause.

 

The core principle is simple. You can't spray your way out of a cluster fly infestation. You have to seal them out.

 

## Cluster Flies or House Flies? Here's How to Tell (and Why It Matters)

 

Cluster flies look similar to house flies at first glance, but they behave completely differently. That's why getting the ID right matters. Treat them like house flies and you'll waste money on methods that won't work.

 

Here's the quick breakdown:

 

| Feature | Cluster Fly | House Fly |
| --- | --- | --- |
| Size | 8–10 mm | 6–7 mm |
| Thorax | Golden hairs visible | Four dark stripes |
| Wing position | Overlaps at rest | Spread outward |
| Movement | Sluggish, slow | Fast, erratic |
| Season active | Late fall through winter | Spring through fall |
| Breeding site | Soil (earthworm host) | Decaying organic matter |

 

The golden hairs on the thorax are the easiest tell. Look closely at a landed fly. If it has those tiny yellow hairs, it's a cluster fly.

 

They also move slowly, almost drunkenly, which is why you can often catch them by hand.

 

House flies are faster and more alert. They appear in summer and breed in garbage or animal waste. Cluster flies breed in the soil outside, feeding on earthworms during the larval stage.

 

That's a crucial difference because it means they're not multiplying inside your home. They're just using it as a winter shelter.

 

![cluster flies vs house flies identification](https://gadgetguides.org/wp-content/uploads/2026/09/cluster-flies-vs-house-flies-identification-mtvpuqe7.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

## How Cluster Flies Get Into Your Home: The Overwintering Cycle

 

Cluster flies spend spring and summer living outdoors. Females lay eggs in the soil, and the larvae burrow down to feed on earthworms. After a few weeks, adults emerge and continue the cycle.

 

They produce multiple generations each year.

 

When late summer arrives, things change. The flies stop looking for mates and start looking for shelter. They're drawn to warm, sunlit walls, especially south- and west-facing sides of the house.

 

As the weather cools in September and October, they crawl into tiny cracks and gaps in the exterior.

 

Common entry points include:

 

- Gaps around window frames and door trim
- Cracks in siding, especially wood or vinyl
- Spaces around utility lines and cable entries
- Soffit vents and attic fan openings
- Chimney gaps and loose flashing

 

Once inside, they settle into wall voids, attic spaces, and eaves. They enter a state called diapause, a kind of insect hibernation. On warm winter days, the heat wakes them up, and they start moving toward windows.

 

That's when you see them crawling lazily across your curtain or landing on a sunny sill.

 

The real problem? They don't all wake up at once. You'll get waves of flies throughout winter, often triggered by a few unseasonably warm days.

 

If you only kill the ones you see, you're ignoring the hundreds still hiding in the walls.

 

## Step-by-Step Workflow: What to Do Based on Your Situation

 

Your next move depends entirely on when you're reading this. Use the section that matches your situation.

 

### If Flies Are Swarming Inside Right Now (Immediate Action)

 

You're dealing with active flies. Here's what to do today.

 

First, grab your vacuum. Use the hose attachment with a narrow nozzle. Go slowly so you don't miss any.

 

Cluster flies tend to gather on window sills, curtains, and the upper corners of rooms.

 

![vacuuming cluster flies](https://gadgetguides.org/wp-content/uploads/2026/09/vacuuming-cluster-flies-mtvpur3s.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

After vacuuming, remove the bag or empty the canister. Seal it in a plastic bag and put it in an outdoor trash can. Dead flies release a pheromone that attracts more cluster flies, so you don't want them sitting in your vacuum.

 

Next, clean the areas where flies were resting. Use a damp cloth to wipe down window sills and walls. This removes any pheromone residue that might attract more flies.

 

Finally, check for any cracks or gaps around windows and doors. If you find obvious openings, seal them temporarily with painter's tape or caulk. This buys you time until you can do a proper exterior seal.

 

### If It's Late Summer or Early Fall (Prevention and Sealing)

 

This is the golden window. You have a few weeks before the flies start looking for winter shelter. Use that time wisely.

 

Walk around the outside of your house. Look for every crack, gap, and hole. Pay special attention to:

 

- Where siding meets the foundation
- Around window and door frames
- Pipe and cable entry points
- Soffit vents and eaves
- Where the chimney meets the roof

 

For small cracks under 1/4 inch, use a high-quality exterior caulk. For larger gaps, use expanding foam. For very large openings, stuff them with copper mesh or steel wool before applying foam.

 

If you have an attic, consider applying insecticide dust to the eaves and wall voids. You can buy a bellows duster for about 15 dollars. Deltamethrin dust is the most common choice.

 

Wear gloves and a dust mask during application. The dust stays active for months, killing any flies that settle in those spaces.

 

### If You Have a Recurring Mass Infestation (Deep Treatment)

 

You've been dealing with cluster flies for years. You've tried vacuuming and sealing, but they keep coming back. At this point, you need a professional.

 

A licensed exterminator will perform a thorough exterior inspection. They'll use ladders and sometimes a thermal camera to find hidden entry points. They'll also treat voids with residual dust that you can't easily reach yourself.

 

The cost for professional cluster fly treatment typically ranges from 150 to 400 dollars, depending on the size of your home and the severity of the infestation. It's a one-time expense that can stop the problem for years.

 

## Common Mistakes That Make the Infestation Worse Next Year

 

Most people make at least one of these mistakes. Avoid them, and you'll save yourself a lot of frustration.

 

**Killing flies without sealing the entry points.** This is the most common error. You spray the flies you see, feel satisfied for a moment, and then a new batch appears the next warm day. The flies already inside your walls will keep emerging until you block their path.

 

**Using outdoor pesticides indoors.** Many general-purpose bug sprays are not labeled for indoor use. They can leave harmful residues on surfaces where you cook or where your kids play. Always check the label.

 

Better yet, use a vacuum instead of spray.

 

**Waiting until winter to seal.** If you're sealing your home in January, you're sealing the flies inside with you. The seal won't stop them from emerging from the walls. Do your sealing in late summer, before they arrive.

 

**Leaving dead flies in wall voids.** This might sound like a minor detail, but it's not. Dead flies attract carpet beetles, which can then infest your home. Carpet beetles feed on organic material, and a pile of dead cluster flies is a perfect food source.

 

If you treat voids with dust, make sure the dead flies are removed or sealed off.

 

**Ignoring the vacuum bag.** The pheromone trail from dead flies tells other cluster flies that this is a safe spot. If you leave the vacuum bag in the canister, you're essentially broadcasting an invitation.

 

## Costs, Timeline, and When to Call an Exterminator

 

Most people can handle a small cluster fly infestation on their own for under 50 dollars. A tube of exterior caulk runs about 5 to 15 dollars. A can of expanding foam costs 8 to 20 dollars.

 

A bellows duster and a container of deltamethrin dust together run about 25 to 40 dollars.

 

That covers a weekend of work. You can seal obvious gaps and treat your attic eaves in a single afternoon. The payoff is immediate.

 

You should see far fewer flies the following winter.

 

If you have a two-story house with hard-to-reach eaves, or if you've already sealed everything you can reach and the flies keep coming, it's time to call a pro. Licensed exterminators charge between 150 and 400 dollars for a cluster fly treatment. That usually includes a full exterior inspection, sealing of hidden entry points, and void treatment with commercial-grade dust.

 

The timeline for professional work is fast. Most jobs take one to two hours. The results last for years if the sealing is done properly.

 

Here's a quick cost comparison:

 

| Approach | Cost | Time Required | Effectiveness |
| --- | --- | --- | --- |
| DIY sealing and dust | $30 to $50 | One afternoon | Good for small infestations |
| Professional exclusion | $150 to $400 | 1 to 2 hours | Excellent for large infestations |
| Vacuuming only | $0 | Ongoing | Temporary relief only |

 

When should you absolutely call a pro? If you see hundreds of flies emerging in a single day, or if you hear buzzing inside your walls. That means a large colony is established in a void you can't reach.

 

A professional has the tools and experience to treat it properly.

 

## Cluster Fly FAQs: Quick Answers to the Most Common Questions

 

### Do cluster flies bite or cause damage?

 

No, they don't bite. They don't feed on your food or your home's structure. They are purely a nuisance pest.

 

The main problem is the mess they leave behind. Dead flies pile up on window sills, and their droppings can stain curtains and walls.

 

### Why do I see cluster flies in winter?

 

They enter your home in late fall to hibernate. That state is called diapause. On warm winter days, the heat wakes them up.

 

They think spring has arrived and start moving toward the windows. That's when you spot them crawling around.

 

### Will cluster flies go away on their own?

 

The ones inside will eventually die. But their offspring will return next fall. Cluster flies don't breed indoors, so you won't get a growing population inside.

 

But the adults that found their way in this year will leave pheromone trails. Those trails attract more flies next season.

 

### Can cluster flies damage my house?

 

They don't chew wood or wires. They don't lay eggs in your walls. But they can cause secondary problems.

 

Large numbers of dead flies in wall voids attract carpet beetles. Carpet beetles feed on the dead flies and can then move into your living spaces.

 

### What smell keeps cluster flies away?

 

There is no proven scent repellent for cluster flies. You'll see claims about lavender, peppermint, or eucalyptus oil. Our research found no reliable evidence that any of these work.

 

Save your money and focus on sealing.

 

### How long do cluster flies live?

 

Adults live for several months. They emerge in late summer, find shelter in the fall, and survive through the winter. Most die by late spring.

 

But multiple generations per year mean new adults are always coming.

 

## The Final Decision Guide: What to Do This Season

 

Here's your decision guide based on where you are right now.

 

**If you are reading this in winter with active flies in your home.** Vacuum them up immediately. Dispose of the bag outdoors. Wipe down window sills.

 

Then mark this as a reminder. You need to seal your home before next September.

 

**If you are reading this in late summer or early fall.** You have a window of opportunity. Walk your exterior and seal every crack. Apply insecticide dust to your attic eaves.

 

Do this now, and you will likely see zero cluster flies next winter.

 

**If you are reading this after a failed DIY attempt.** You sealed everything you could find. You dusted the attic. The flies still came back.

 

Call a professional exterminator. They have the experience and equipment to find the gaps you missed.

 

**If you are a renter dealing with cluster flies.** Your options are limited. You can't modify the exterior of the building. Focus on vacuuming and sealing gaps inside your unit with temporary caulk or tape.

 

Report the issue to your landlord. Cluster flies in one unit often mean the whole building has entry points.

 

The bottom line is simple. You can keep cluster flies out of your home, but you have to be proactive. Waiting until they appear guarantees a longer fight.

 

Seal in late summer, treat the voids, and you'll win next winter.