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How to get rid of cluster flies?

Cluster flies can be nasty nuisances if you don't kill them early and let them assemble in and outside your house.

December 28, 2021

16 min read time

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Few things are as irritating, unhealthy, and potentially destructive as pests.

That is why no one is exactly happy when they notice they have an insect infestation.

Imagine having a blast of a party, and you and your guests constantly have to swathe at big fat flies swirling around your drinks and food.

No one likes that. That is why we have come up with an article on how to get rid of cluster flies. But before we proceed, let’s show you how to identify cluster flies.

What Are Cluster Flies

Most people often mistake cluster flies for house flies, except they are slightly larger and move a lot slower. Their appearance is also different. You can identify them by the golden hairs on their black bodies and a light and dark checkered pattern around their abdomen.

If you look closely, you will find that their wings overlap when they rest.

But tellingly, the cluster fly gets its name from its propensity to congregate in large groups. These pests are also called grass flies because they are often found moving around on the floor or in the grass outdoors.

Are Cluster Flies Bad?

Not really.

Cluster flies are not known to have any direct adverse health effects on humans.

However, they have the potential to be highly irritating in their large numbers.

In such numbers, they produce a significant amount of fly excreta that can contaminate your food, stain walls, windows, floors, and belongings. Then there is that solid and unpleasant odor that they give off when they are rattled.

Besides the high nuisance factor of their large gatherings, these flies do not pose any serious health risk as they are not known to bite people or pets, neither are they known to spread bacteria or lay eggs inside your home.

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What Causes Cluster Flies In House?

Unlike most flies that are drawn to refuse, the cluster fly loves light and warmth. That is why you find flies in your home during the autumn and winter. Once fall comes, they gravitate towards environments that offer light and warm which your home provides.

So these breeds of flies in your home come because of your indoor lighting and your heating arrangement that makes your home comfortable during the cold season. That is why you often find them inside your house, where they usually stay until after the cold weather gives way to the warm season.

Once they are in, they cluster together in the lesser-used areas of your house, like your attic, and can often find their way into the tiny cracks and holes in your home’s façade during the winter season.

However, once the weather becomes warmer, like during spring, you might find them exploring other parts of your house. If they find your house a great location to hibernate, they will leave pheromones that attract other flies to come over to your home to hibernate.

The good news is that once you know what draws them into your house, you get rid of them using the right pest control method.

How Long Do Cluster Flies Stay?

Compared to other insects like house flies that do not live up to three months, cluster flies live for a long time.

Cluster flies have been known to live for up to two years and more. They can do this because they hibernate to get past the cold months. The thing is that their favorite haunting spots for hibernation are often our homes.

So how long do cluster flies stay?

As long as you let them.

They don’t just die off or leave your house when they are tired of the warmth and light that it offers them. They stay for as long as they can. Their life cycle follows a somewhat predictable pattern.

The adult female cluster flies lay eggs in the soil. The eggs in the soil hatch to become larvae that seek and feed on earthworms. After getting its fill from the earthworm, the larvae leave the worm to pupate in the soil, after which it becomes an adult fly. This happens throughout the summer.

By fall, the cluster flies seek shelter in homes and buildings that provide the warmth and light that they need to wait out the cold months. They only leave these buildings during the late summer and spring.

Cluster flies can stay on for years without being detected as they generally stay out of the way, and you might only notice them when their numbers have reached alarming proportions.

Or when they crawl out of the cracks and crevices in the wall voids on warm winter days or when the warmth in your home tricks them into thinking the cold months are over.

Most times, during hibernation, cluster flies are catatonic, but they will not go away if you don’t use some pest control method against them.

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How Do You Get Rid Of Cluster Flies Naturally?

There are different pest control methods for eliminating this breed of fly, but we will be looking at the natural pest control methods used to get rid of them. Here are some of them

1. Use a vacuum

You could use a vacuum cleaner to eliminate cluster flies because they don’t move very fast, so it isn’t easy to vacuum them.

Target around windows and the cracks around the house and other places that fly cluster. A hand-held vacuum cleaner will help, but you want to empty the vacuum outside your home as soon as it is full.

2. Use cluster fly traps

You could use a Mason jar with some sweetened water and a perforated lid to lure and trap cluster flies. Or you could opt for a 2-liter soda bottle by cutting the bottle in two and putting the top upside down in the bottom section. You then leave something sweet so that when the cluster flies go down into the trap, they can’t come out.

Another great cluster fly trap is the Cluster Buster that comes with translucent walls and finely ground eggshell that pulls the flies under and clogs their respiratory systems.

flea trap

3. Use carnivorous plants

These plants can kill and control cluster flies, as they attract insects and eat them, after which they dissolve their bodies. Some examples of carnivorous plants are Venus flytraps and Pitcher plants.

4. Light traps & zappers

Since cluster flies love light and heat, you could use zappers that attract and electrocute them. The electrical charge from these gadgets is not strong enough to harm you or your pets. Light traps are also another great option as they are designed to trap the flies drawn to the light instead of electrocuting them.

They are essentially small but high-intensity UV lamps with adhesive glue boards. Cluster flies that are attracted to UV Light get stuck on the glue boards.

5. Spray a pyrethrin-based aerosol insecticide

This insecticide is made from natural plant extracts and is safe for use around the house. It would be best to focus on windows or any wall or areas like your attics where there might be a fly cluster.

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How Do I Permanently Get Rid Of Cluster Flies?

The best way to permanently eliminate cluster flies is to eliminate anything that draws them to your home or environment.

So your approach should be a proactive, preventive control method. Here are some suggestions that you might want to consider:

1. Keeping the drainage in good shape

Well-maintained drainage will reduce the nuisance of cluster flies around you because they need some surface water. When you fix the drainage, you eliminate standing water that could attract them.

2. Check screens

You want to make sure that the screens around your house are in good condition, too, as cluster flies can sneak into the minor gaps in them. Thankfully screens are cheap, so you can easily replace them when they go bad.

3. Clean trash bins and dumpsters

Ensure that your dumpsters and trash bins are not overly messy because cluster flies love dirty, putrid trash bins with rotten food. An excellent way to keep your trash bins and dumpsters in good condition is to use Lysol, citronella insecticide sprays, and vinegar solution treatment.

4. Do some proactive  indoor spraying

Cluster flies are often drawn to homes around the fall season, so about that time, you want to spray an insecticide on those areas in your house where you suspect cluster flies frequently. Say windows and corners.

We recommend that you use pyrethrin-based aerosol insecticides since they are less harmful. Focus on the surfaces of walls and other spots.

You also want to make sure you apply residual sprays on the exterior areas where you keep your trash with insecticides because it is one haven for cluster flies during the warmer months when it is sunny.

5. Clean and seal your home

Seal the small cracks or gaps in your home because cluster flies love these places. You could use caulk or spray foam insulation to block these cluster fly havens. Take a good look at your windows too. Clean and declutter your home(especially the attic)as often as possible.


Cluster flies can be nasty nuisances if you don’t kill them early and let them assemble in and outside your house.

Thankfully, they are easy to control. You could use the right treatment before they lay eggs that hatch once you know-how.

We hope you apply the tips described in this article so that your home and environment can be free of these fat, black flies.

Another option is to get the services of professionals.

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