How to Get Rid of Cluster Flies in House Once and for All!

Four useful tips on dealing with cluster flies with three prevention measures.
Phyllis McMahon
Phyllis McMahon
Research Writer
Phyllis teaches English Literature at a local college and loves writing in her free time. She’s also a great cook – her British beef Wellington is something the best res read more
Reviewed By
Chas Kempf
Chas Kempf
Expert Consultant
Chas works in a professional pest control company and knows all the nuances of this job. Also, he’s a fantastic tennis player and loves to organize BBQ parties for his fam read more
Last updated: September 02, 2023
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There are few things more irritating than pests. They’re also unsanitary and no one likes looking at them. It’s especially bad when you find you’ve got an infestation rather than just one or two, and it’s the same when you have an issue with cluster flies. The question arises: how to get rid of cluster flies?

Appearing in spring, cluster flies will begin to lay eggs outside and will hibernate in your home around nearing winter, around August time. To get rid of cluster flies you can use your vacuum cleaner, aerosol fly killer or call your local professionals who will be able to use smoke bombs or foggers for more effective results.

How to Identify Cluster Flies

They are 8mm in length and they’re dark grey in color, having small gold hair patches on their long wings and back. The biggest sign that you have an infestation of cluster flies is seeing a lot of dead or lame flies. You also may find them in a loft, underneath layers of insulating felt, or in spotlighting. They usually will return on a yearly basis unless you adequately seal entryways like eaves.

Cluster and House Flies

How to Get Rid of Cluster Flies in House Once and for All!
Generally speaking, cluster flies are bigger, darker, and slower than house flies.

What are the differences between cluster flies and house flies?

  • Color and Size – Cluster flies’ bodies are black and have a pattern that looks like silver checkers. House flies, on the other hand, have a dark grey body and 4 narrow stripes in black running on their bodies. House flies are only 3-6mm in length compared with the 7mm length of a cluster fly.
  • Wings & Flight – The flight of a cluster fly is less frantic and much slower than house flies. The wings of cluster flies overlap while resting and houseflies’ wings stay separate.
  • Behavior – Cluster flies cluster together. They’re often found clustered together around windows. In an attic, they’re found in a sunny space. They’re attracted to light and warmth.
  • Habits – While house flies enter homes looking for water and food, cluster flies mainly live outdoors and come inside during the late part of summer and the early part of fall to find somewhere to hibernate.
  • Disease – Cluster flies aren’t known for carrying and transmitting diseases or damaging structures. They also won’t reproduce once they enter a home. Houseflies carry many diseases because they land and feed on poop and garbage.

Preventing Cluster Flies

How to Get Rid of Cluster Flies in House Once and for All!
Spraying insecticide and fixing your door and window screens are effective ways of preventing cluster flies in your house.

The best thing that you can do to avoid the problems of cluster flies is to prevent them from coming into your house.

Seal Your Entry Points

This is going to help with preventing them from coming inside. These are small pests, so you shouldn’t overlook small holes. These are areas that you should give special attention to:

  • Gaps & Cracks – Check your home’s interior and exterior for any gaps and cracks. Seal them using caulk. This will help keep these pests out.
  • Weather Stripping – Make sure your weather stripping doesn’t need replacing. If so, make sure you replace it to help stop the flies from getting in.
  • Door and Window Screens – If your window and door screens have holes in them, replace or repair them.


One thing that cluster flies love is an undisturbed location. If your house is unorganized and messy, it gives them with a lot of spots to hide. Make sure that you’re taking time to keep the house clean. If you have an attic, chances are that there is a lot of stuff up there. So you want to make sure that you are keeping your attic organized too. This is also going to help with minimizing areas where they’re able to hide.

Create a Barrier

You can also spray your home’s perimeter with an insecticide spray that is plant based. This creates a barrier around the home that is going to help with keeping the cluster flies from getting in.

How to Get Rid of Cluster Flies Inside

Ok, so you know how to prevent cluster flies from getting into your home. However, what if you have read this article too late and you need to know how to get rid of cluster flies that are in your home? Here are a few things that you can do.

Vacuum or Swat the Evident Flies

How to Get Rid of Cluster Flies in House Once and for All!Do you want to know how to get rid of cluster flies with home remedies? The good news is that there are things that you can do using something that you already have in your house. Since they’re sluggish when compared with houseflies, it’s usually pretty easy to vacuum or swat the ones that you see. Some of the best electric fly swatters will do the job perfectly. After you’ve killed some, chances are that there are going to be more that you see coming out which means that you are going to repeat the process of vacuuming and swatting. However, eventually the ones that are left are going to die while they try to find the exit.

Utilize Traps

How to Get Rid of Cluster Flies in House Once and for All!Don’t want to keep vacuuming and swatting? The good news is that they also can be managed using sticky traps or flypaper. You also can make a solution of sugar water and put it into a jar. The opening should be just big enough for them to get into it. Like any kind of fly, they love sweets. Just make sure the jar’s emptied regularly. Some of the trap from our best yellow jacket traps article might fit in here too.

Spray Pesticide

How to Get Rid of Cluster Flies in House Once and for All!Since you are using it indoors, you want to choose a pesticide that contains pyrethrin. This is based on a chrysanthemum flower extract. It’s going to quickly kill the cluster flies. They’re found in many commercial products. It should be used lightly, directly aiming at the flies.

One thing that you should note is that these pyrethrin aren’t totally harmless. They will harm fish, so they should be kept out of the water supplies. However, their toxicity is low for humans as well as other kinds of mammals. Make sure that you’re using products that list pyrethrin rather than pyrethroids as an ingredient. Pyrethroids are synthetic.

Some of the suitable pesticides are listed in our guide on the best earwig killers, so check it out.

Seal Interior Cracks and Gaps

How to Get Rid of Cluster Flies in House Once and for All!If you want to jump on the problem now before they start hibernating instead of having to search for how to get rid of cluster flies in the winter, now is the time to seal those interior cracks and gaps. Those cluster flies which are already inside thanks to the exterior crevices and cracks won’t be a problem inside unless you also have interior wall gaps. Even tiny cracks along your door and window frames and around your baseboards can give them a way to get into your home.

Keep getting rid of the cluster flies by filling all of the crevices and cracks in your homes inside wall surfaces, which include:

  • Around the windows and doors
  • Around vent registers
  • Around the electrical outlets
  • At those points between the floor and baseboards

This is going to help you with preventing the new cluster flies from coming out as you’re killing those that are already in the house.


Are there any homemade methods of dealing with cluster flies?

Do you want to know how to get rid of cluster flies naturally outside? One of the best ways that you can attract cluster flies and trap them is by making a solution of sugar water and putting it into a jar. Then have an opening on the jar just big enough to let the flies to get into it.  This is a great option for when you are looking for how to get rid of cluster flies with DIY options without having to call an exterminator.

Why do I have cluster flies?

They can crawl through tiny openings inside your home’s walls. These kinds of flies will go into homes and look for places where they can hibernate during the winter. They prefer the warm areas, so you will many times find these pests flying around your home on the sunny days in the later part of fall and in winter.

They often will get into a house through a baseboard or electrical outlet and will take up shelter inside walls and the attic. Here is where they will await the warmer weather of spring. On sunny days during the winter, the walls could become warm so these inhabitants might try moving towards light.

Are they a serious problem to have?

Cluster flies, unlike houseflies, don’t carry disease. So even if you are looking for tips on how to get rid of cluster flies in your garage, you don’t have to worry about getting sick because of them. it’s also good to know that they also aren’t going to cause your home any extensive damage. But they might make your windows or walls dark with droppings. They also could attract other kinds of insects if they should di in the voids of the walls. Large cluster fly numbers often will collect in ceiling lights and windows, which makes them a pain in the neck to deal with.

Final Thoughts

Thank you for taking the time to read our article and we hope that you know how to get rid of cluster flies in your house now. So, even though cluster flies are not as much of a problem as houseflies, as in they don’t carry disease, they still can be a pain to worry about coming into your home. We hope that you found this to be useful and that we’ve helped you understand a bit more about one of the most annoying pests that you can have in your house – cluster flies.

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