How to Get Rid Of Cluster Flies

Flies are a pest in any house. Cluster flies are no different. 

You’ll find these flies in large grounds inside or outside of your home trying to find somewhere to hide. 

Although you won’t find them flying inside your trash or all over your home they are still difficult to get rid of. 

In this post, I will go over how to identify cluster flies and what you can do to get rid of them. 

Let’s dive in. 

What Are Cluster Flies?

Cluster flies and house flies are often confused, but they shouldn’t. Cluster flies are different species of flies. 

They are commonly referred to as attic flies because they tend to hide in attics. These flies are parasitic on earthworms.

These flies tend to seek out calm and undisturbed areas of a home where they can seek shelter. They tend to try to avoid humans and animals.

During summer, these flies are active, and you can typically find them above the burrows of earthworms.

In fall, these flies will seek out areas where they can stay protected during winter. They remain relatively inactive during winter and stay in the protected areas they found.

How To Identify Cluster Flies?

Identifying different fly species is not an easy task. It’s hard to get close to flies without moving, which makes it hard to identify key characteristics. 

There are key characteristics that will help you identify cluster flies from other species of flies. 

Some key characteristics of cluster flies are 

  • Color: Grey in color 
  • Size: 8 – 10 mm long 
  • Hairs: yellowish golden hairs on their thorax 
  • Abdomen Pattern: dark and white chequered pattern 
  • Wings: Their wings overlap across the abdomen 
  • Odor: sweet odor when disturbed similar to honey 

Seal Your Home

Cluster fly infestations start outdoors. If there are cluster flies outdoors, they will eventually try to enter your home.

You will experience groups of these cluster flies trying to get inside your home during winter.

The first thing you need to do is to seal any entry points around your home.

You can do a few things to seal up your home to make sure cluster flies can’t enter your home.

Fix And Replace Screens

The first thing you can do is to replace or fix the screens in your home. Often small holes or tears in window screens and door screens will allow cluster flies to enter your home.

The standard mesh screen will keep mosquitos out as long as there are no holes or gaps in the screen.

It’s also essential that you have correctly fitted screens in the first place. Screens that are bent and create gaps will give cluster flies the opportunity to enter your home.

It’s important that you also fix or replace screens. These are often overlooked but are a primary entry point.

Weather Strip Your Home

It’s also vital that you properly weatherstrip your entire home.

Pay special attention to doors and windows. The gaps around your door or window sills can allow cluster flies into your home.

The first step to weatherstripping your home is to apply door sweeps at the bottom of your door.

The second step is to apply foam strips to your door and window frames. This will prevent cluster flies from entering through any small gaps around your doors or windows.

I also recommend that you apply covers to basement and attic vents. Since these vents are in uncommon locations, they often get overlooked.

Cluster flies can enter these vents and hide inside your attic or crawlspace. These entrances often get overlooked because people don’t inspect their attics or crawl spaces often.

Over time, these vents can get damaged or be completely missing.

Be sure you also apply coverings and screens to attic or basement vents.

Seal Holes And Cracks

You also want to make sure you cover any holes or cracks around your home. The easiest way to fill holes and cracks is using caulk. Caulk offers easy application and quick drying.

Cracks and holes can act as an entry point for cluster flies.

Focus on areas around your windows and doors. Sometimes cracks and holes tend to form around window rails and casings.

Just like windows, doors typically emit light that attracts mosquitos. Any potential entry points will leave your home vulnerable to flies.

Use Traps

Mosquito traps can be used both indoors and outdoors. These traps are effective on all flying insects.

Suction traps are particularly effective against cluster flies because they are not strong fliers.

Since they are relatively slow fliers, you can also position the trap to capture as many flies as possible.

If the clusters have already started, then you can position the trap next to the cluster of flies.

The heat and light that the trap emits will attract the cluster flies. When they start flying toward the trap they will get sucked in by the suction.

Most people think of the traditional glue paper are the best way to trap flies.

I don’t recommend these traps. These traps are outdated and ineffective.

Today there are special traps made for indoors. These traps are discrete and effective. The most effective traps use several different types of lure to attract mosquitoes and trap them.

These traps are also great because they work on moths, flies, and other flying insects.


Avoid using mosquito zappers indoors. While they are effective, they are not sanitary to use indoors. Mosquito zappers cause mosquito remains to be disbursed into the air and nearby items.

Indoor traps should be a combination of lures with vacuum suction or sticky pads. This keeps your house sanitary while getting rid of mosquitoes.

Use Bug Zappers

Bug zappers are the most traditional way of getting rid of flying insects such as mosquitos and flies.

Bug zappers are still effective on cluster flies because they are attracted to heat and light, just like other insects.

Once they enter the bug zapper, they will die.

It’s important to keep bug zappers away from the area that people frequent. The dust and particles that are released when a bug is zapped can leave dangerous bacteria.

Use Chemical Insecticide

Chemical insecticides are one of the most common choices to get rid of flies or other flying insects. 

There are two types of chemical insecticides you can use to get rid of cluster flies. 

  • Liquid Insecticide 
  • Aersol Insecticide Spray 

Liquid Insecticide / Foggers

You can use liquid insecticides outdoors in your yard and on the surface of your home. I recommend spraying the entire surface of your home.

Cluster flies often group up in high positions around homes, including eaves, attic vents, and other areas around your home.

You can also apply insecticide to your grass and soil. I recommend applying insecticide anywhere you see cluster flies swarming.

This will ensure that any cluster flies that land on the ground where you live will eventually die.

Aersol Spay

I don’t always recommend aerosol sprays when dealing with flies, but cluster flies are an exception.

In particular when they are inside your home. Inside your home, if you can locate the clusters of flies, you can spray them directly.

The best insecticide is one with a high and quick knock-down rate. This will ensure that you kill the flies fast and effectively.

Use a Vacuum

Vacuums are another effective way you can get rid of cluster flies if they are already clustering inside or outside your home.

With most species of flies, this method is ineffective because they can fly to fast. Cluster flies are weak and slow fliers which make vacuums a perfect tool to get rid of them.

I recommend you get as close as you can to the cluster. Once you are close, turn on the vacuum and suck up as much as you can.

You can continue vacuuming them even after they have been disbursed. I recommend closing off the cluster area to ensure that they don’t spread to other areas of your home.

Get Rid of Earthworms or Control Population

Cluster flies are unique because they prefer to lay their eggs in soil where groundworms are present. 

One way you can reduce and get rid of cluster flies is to reduce or eliminate the number of earthworms around your home. 

Eliminating earthworms is not an easy task, especially since they are regarded as primarily beneficial insects. 

There are a few things you can do to reduce the earthworm population in your yard. 

  • Apply fresh soil after it rains
  • Water your soil to drive earthworms deeper into the earth 
  • Keep your yard well maintained 
  • Role your lawn frequently 
  • Rake and sweep your yard often to eliminate organic waste, including casings

Frequently Asked Questions (FAQ)

How Long Do Cluster Fly Infestations Last?

Cluster fly infestations typically only invade homes or cluster up during fall and winter. Typically the infestations will start in fall and reach maximum size during winter.

Once winter passes, cluster flies will leave the area where they spent winter and seek out earthworm burrows so they can begin mating and laying their eggs.

What Causes Cluster Fly Infestations?

There are only a few things that cause cluster fly infestations indoors or outdoors. 

Outdoors there are two common reasons why you might have a cluster fly infestation. 

  1. There is a rich eathworm population around your home – including burrows 
  2. Your home has rich soil that supports plenty of burrowing insects 

Indoors there are really only two reasons that you have a cluster fly infestation

  1. It’s spring or winter, and they have found a protected area to protect themselves from the cooler temperatures 
  2. There are easy entry points around your home, and cluster flies have entered your home 

What Do Cluster Flies Eat?

Cluster fly larvae and adults have two different diets.

Cluster fly larva survives on earthworms. Cluster flies lay their eggs in the soil near earthworm burrows. The larvae will burrow into the soil and feed on earthworms.

Adult cluster flies feed on nectar and sap from flowers and plants. They can also survive on other organic matter.

Unlike most flies, they are not associated with garbage or feces.

Do Cluster Flies Lay Eggs In Houses?

Cluster flies don’t lay eggs inside houses. They only lay their eggs inside fresh soil, specifically where earthworm burrows are present.

Typically, cluster flies only enter homes during spring and winter. During these seasons, they don’t matter. They remain relatively inactive until the weather begins to warm up, and they can begin mating again.

Will Cluster Flies Eventually Go Away?

Cluster flies will eventually go away if they are indoors. They only go indoors during winter to survive the winter. They will ultimately leave your home once the weather begins to warm up.

During summer, they will leave your home in search of fresh soil to begin mating and so they can lay their eggs.

Outdoors cluster flies will go away during winter and hide.

But these flies will return to the same areas, especially if the earthworm around your yard reminds high during summer and spring.

Why Do I Have Cluster Flies In My House?

Cluster flies are inside your house because it’s winter. During winter, cluster flies will enter your home for protection against the cold weather.

They will spend winter hiding and mostly inactive during the winter. Once winter is over, they will resume their activity outdoors.

How Long Do Cluster Flies Stay In House?

Cluster flies will only stay inside your home during spring and winter. They enter structures and homes to find warmth and protection from the cold weather.

Once the weather begins to warm up, typically during summer, cluster flies will leave your home.

During summer, cluster flies will become active again. Typically cluster flies will attempt to return outdoors to begin mating, laying their eggs, and foraging for food.

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