How to Get Rid of Cluster Flies? These 4 Methods Will Help

Alvin Hamblin

By Alvin Hamblin

Last Updated on February, 2025

Having cluster flies inside your home is not a pretty sight. Not only are they larger than the average house fly, but their tendency to cluster can result in large numbers of flies entering your home during winter, early fall, or even the summer. 

The good news is that cluster flies do not spread disease and are not a health concern. However, unless you encounter a fly that pays rent, they are still troublemakers that need to be evicted.

This article will show you how to stop cluster flies from entering your home and how to remove them if they’ve already taken residence. 

Let’s begin! 

Quick Summary

  • There are multiple methods for getting rid of cluster flies, such as using traps, fly swatters, light traps, and insect spray.
  • Cluster flies are larger and tend to cluster, making them a nuisance in the home during certain times of the year.
  • Preventative measures, such as sealing entry points and keeping the home clean, can help avoid a cluster fly infestation.

How to Get Rid of Cluster Flies?

a picture of multiple cluster flies caught using a fly trap paper

Like with most pests, you can take specific measures to eliminate cluster flies. Here are four proven methods to solve your cluster fly problem.

Use a Fly Swatter or Vacuum

Electric swatters are a popular and effective way of eliminating house flies. Since cluster flies are slightly larger, they move sluggishly through the air, making your job easier.

A mini vacuum cleaner can also be good for the job. Remember that doing this will leave a lot of dead flies, so ensure that you vacuum your carpet thoroughly once you’ve swatted all the visible pests. 

Create Fly Traps

Cluster flies are attracted to sugar, and you can use sweets, syrups, or overripe fruits to lure and trap them. While flypaper is the ideal way to do this, you can also fashion traps out of bottles or glass jars.

Trapping is simple and effective and lets you get rid of cluster flies using readily available food items instead of insecticides. 

Set Up Light Traps 

A light trap is a device that uses ultraviolet light to attract and capture insects such as moths and flies. They also have a built-in mechanism to dispose of these pests once captured.

Examples include black lights, mercury lamps, and fluorescent lamps. Since cluster flies gather near windows, placing the light trap on nearby walls lets you remove them in large numbers. 

Use an Approved Insect Spray

An indoor fly killer spray provides the quickest and most straightforward way to eliminate your fly problem.

While effective, insect spray also contains pyrethrins, which can be toxic to humans if inhaled. When using it on walls or windows, spray directly at the flies while avoiding other areas. 

How to Identify Cluster Flies?

close up images of a cluster fly

While it can be easy to mistake cluster flies for normal house flies, there are some notable differences between them. 

Size: The average house fly measures 3-6mm long, while a cluster fly can reach 7mm. 

Body Colour: Cluster flies are darker with a silver chequered pattern on their abdomens. Their most distinguishing feature is the thorax, which contains golden or yellowish hairs, unlike the dark stripes common to house flies. 

Wings: If you observe a cluster fly at rest, you will notice that their wings are overlapped across their abdomen. In contrast, house flies often spread their wings, even when stationary. 

Movement: Cluster flies move slower through the air compared to regular flies. 

Clustering Habits: Cluster flies gather in groups on your walls, often near glass windows or doors. This behaviour makes them easy to identify. 

Other useful guides:

Interesting Facts About Cluster Flies

When dealing with bugs and insects, it doesn’t hurt to learn more about them. Here are some interesting cluster fly tidbits that you might not know. 

  • Cluster flies are sometimes called attic flies because they gather in attics, false ceilings, or high walls once indoors. They are also called grass flies because their larvae feed on earthworms in the soil.
  • Though cluster flies hibernate inside your home, they do not reproduce indoors. Instead, they lay eggs close to earthworm burrows in the soil. Once the eggs hatch, the larvae feed on the worms until they become pupae. Larvae generally take 33-36 days to develop into adult flies. 
  •  Cluster fly larvae will feed on earthworms, but flower nectar is their primary food source when they reach adulthood. 
  • A cluster fly will begin its life cycle outside. Once they reach adulthood, they breed, and females lay eggs in the soil. During the fall and winter, the flies move into houses or buildings for hibernation. They reemerge in early spring or during unseasonably warm weather in the fall, and repeat the process. 
  • With the right living conditions, a cluster fly can survive for two years before reaching the end of its life cycle. 
  •  While common in the UK, cluster flies are also found throughout Europe, Australia, and North America. 

How Do Cluster Flies Get in the House? 

an image of a cluster fly sitting on the edge of a windowsill inside a home

Cluster flies commence their indoor activity in late summer or early fall. Hiding away before winter arrives is a crucial part of their life cycle. During this period, they can use several potential entry points to invade your home. 

They can fly in through open windows, unscreened doors, and unsealed vents. They may be bigger than house flies, but that doesn’t mean they can’t find ingress through cracks in your windows or door frames. 

Cluster flies seek refuge in warm, sheltered areas to hibernate, often hiding in gaps and crevices in your home. These include electrical outlets, wall voids, and chimneys. 

Once they settle for hibernation, they typically won’t reemerge until the following spring, which means it’ll be a while before you become aware of their presence. 

Problems Caused By Cluster Flies

You shouldn’t overreact if you find cluster flies inside your building. Since they don’t breed or lay eggs when inside, they don’t pose much health risk. However, they can still be a nuisance. Here are a few ways these flies cause trouble. 

Dirty walls and curtains: Hibernating cluster flies produce excrement that leaves stains on walls, curtains, and windows. The excrement also creates an unpleasant odour, mainly because of the large number of flies. 

They are noisy: Gathered cluster flies make a loud, buzzing noise that can be irritating. 

Food contamination: Cluster flies pose a contamination risk in places like restaurants due to their exposure to human food. 

How to Prevent a Cluster Fly Infestation?

Targeted applications like fly killer spray may effectively remove these insects, but only provide a temporary solution. You might be free of pests momentarily, but what about when they return? 

The best way to make this problem disappear is to prevent cluster flies from entering your building in the first place.

While cluster flies usually arrive in the fall or winter, they can sometimes enter your home in the late summer months. As such, you should take preventive action as early as the spring. 

Instead of contact spray, consider residual insecticides like Cyzmic CS or Bifen IT. These sprays remain potent for long periods, making them an effective repellent. Use them on window gaps, wall voids, and outside walls.

However, remember that dead flies can attract pests like beetles and rodents. You should take necessary measures to protect your home and walls from such threats.

Another thing you can do is keep your home vacuumed and dry, as cluster flies can be attracted to food particles or drink stains on your carpet.

Sealing your food will also help. Additionally, these flies are drawn to stagnant water, garbage, and pet faeces. Keeping the outside of your home clean and free of odour will go a long way in preventing an infestation. 

While these measures can work, removing access to your home is the best long-term solution for your cluster fly problem.

Seal cracks around your window frames, door frames, electrical outlets, light switches, etc. You can also install screen doors and fly mesh for windows. We recommend fibreglass for the latter, as it is affordable and rust-resistant. 

When taking these measures, pay particular attention to the parts of your building facing south and west. These areas get the warmest and are the most likely to attract cluster flies. 

a professional pest controller applying pesticide underneath a white cabinet

When to Call a Professional Pest Control Service?

There may be several ways to deal with cluster flies yourself, but these measures are less effective than using a fogger or smoke bomb. Both appliances produce fumes that exterminate insects instantly and put a swift end to your infestation. 

Unfortunately, the fumes produced are toxic to humans, meaning that only pest control experts wearing protective gear can use these methods. 

As such, if you encounter a cluster fly problem and want it solved as quickly as possible, you should call us at 783 030 4098. We will save you the time and trouble of doing the extermination yourself. 

Conclusion

While cluster flies are harmless and do not carry disease, they can be a nuisance once they enter your home. You can take some easy steps to eliminate them yourself. However, precautionary steps like sealing ingress points and maintaining hygiene let you avoid the problem altogether. 

If you missed out on these steps and suspect a cluster fly infestation, then don’t worry. Give our local pest control service a call for assistance; we’ll get you cleaned up and insect-free in no time.

Good luck! 

FAQs

Cluster flies typically invade homes in the fall seeking warmth for the winter. If you suddenly have them, it’s likely because they found entry points into your home while searching for a place to hibernate.

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