How To Get Rid Of Cluster Flies

September 21, 2021

Home / The Orkin Blog / How To Get Rid Of Cluster Flies

Though cluster flies (sometimes referred to as black eyed or lethargic flies) do not pose a significant health threat, they can be a nuisance. Named for their tendency to cluster together in groups while overwintering indoors, these insects can take over your home or business if not dealt with right away. Using over 65+ years of pest control experience, we’ve put together some of the most effective tips to get rid of cluster flies in your home or business.


What Do Cluster Flies Look Like?

Adult cluster flies are dark grey in colour, 8 to 10 mm long, and have numerous golden or yellowish hairs on thorax. Despite bearing a strong resemblance to house flies, cluster flies are larger in size and darker in colour, they lack the dark stripes found on thorax of house flies and the metallic coloured shining bodies of bottle flies.

They can be considered sluggish when moving (commonly identified as lethargic flies) compared to house flies and bottle flies. The wings of cluster flies overlap across the abdomen when the insect stands at rest.

How Did Cluster Flies Get Inside My Home/Business?

Cluster flies are most visible during fall (September) as the days shorten and weather becomes cool. Typically, these pests look to enter your home or business in order to hibernate as the temperatures drop and winter approaches.

These pests find their way in through openings in the wall, like cracks and crevices near window and doorframes, open and unscreened windows, and unscreened vents that provide access into the building.

Common Signs of Cluster Flies

Like their name suggests cluster flies, do in fact cluster together making it easier to recognize if these pesky flies have invited themselves into your home or business. The first sign of cluster flies is when they gather in numbers on exterior walls, particularly south facing walls that get much sun and warm. You may also notice that on warm sunny days, they emerge and cluster on windows attempting to get outdoors.

They can commonly be found in protected areas of your house or business, such as attics, lofts, sheds, garages and basement areas. You may also notice stains on windows and curtains in areas where there is high cluster fly activity, this is actually cluster fly droppings.

Risks Associated With Cluster Flies

Unlike house flies, these pests may not present a disease risk, but you’re not out of the woods yet. This is because cluster flies can attract carrion-feeding insects if they die inside wall voids and other hard to reach areas. These pests can also cause a nuisance when large numbers congregate in common areas of your home or business such as on windows, doors and in kitchen and pantry areas. This occurs on warm sunny winter days making them a major nuisance and contaminants. When they congregate, you can also expect your windows and walls stained with droppings.

How To Get Rid Of Cluster Flies

When trying to get rid of cluster flies in your home or business it is important to follow these tips:

  1. Prevent them from clustering on your exterior walls and eventually going inside. If home or business is in an area prone to cluster flies, an exterior perimeter treatment is the first prevent step, should be done by professional. it will create a barrier and get rid of any cluster flies as they gather on the wall surface hence prevent entry all together.
  2. During the early fall, it can be important to perform an exterior inspection of your property. Focusing on areas around your home or business that may be an entry point for cluster flies. You will want to be on the lookout for any cracks, gaps, areas around loose fitting electrical outlets or switches, loose baseboard and other potential entry points. Once you’ve located the openings, it is important to seal the cracks to keep vulnerable areas such as behind baseboards, around windowsills and near doorframes.
  3. Cluster flies also love the sunlight and warmth, which is often why they buzz against windows. Always make sure that any open windows have mesh screens to keep cluster flies, along with other insects from entering. It is also important to avoid keeping doors without screens open for long periods of time because this can create an easy unprotected opening for cluster flies to come inside your home or business.
  4. For any visible cluster flies, they can be vacuumed up. If there is a larger population of cluster flies indoors, using a fly light trap can be just as effective to control the population. When using the fly light trap, it is important to place the trap in areas where cluster flies are most active to see the most effective results.
  5. When possible seal any exterior gaps and cracks around windows, doors, eaves, siding and utility pipes.
  6. Repair or replace all damaged screens on doors or windows where possible.

We hope you find these tips helpful in your quest to rid your home or business of cluster flies.It is important to remember that you’re not alone. If your cluster fly issue seems too daunting for you to deal with on your own, your local Orkin Canada technician is happy to assist you. Contact Orkin Canada today for effective and reliable fly control you can trust.

Remove pests from your home, and stop them from coming back

We work hard to listen, understand and assess your unique situation. Request a free, no-obligation estimate today for a customized pest program that fits your needs.

Request a Free Home Estimate
Request a Free Business Consultation

Reviewed by Alice Sinia, Ph.D., MSc on September 19 2021.

You may also like

Ontario's Top 25 "Rattiest" Cities 2021

Pest control leader Orkin Canada reminds home owners and business owners to take precautions to help keep rodents out. Cities are ranked by the number of rodent (rat & mice) treatments the company performed from August 1, 2020 through July 31, 2021. This ranking includes both residential and commercial treatments.

5 Tips To Get Rid Of Fruit Flies

To some, fruit flies are probably the most headache inducing pest to deal with. What these flies lack in stinging or biting power, they more than make up for in being a consistent nuisance in your home or business. Using our industry knowledge and expertise, we have put together five easy tips to keep fruit flies out of your kitchen. 

What You Need To Know About Rodents During The COVID-19 Pandemic

The impact of the COVID-19 pandemic has been immediate, and long lasting, with businesses having to adjust the way operations take place. While for you and I the impact has been quite easy to see; from wearing masks and carrying sanitizer wherever you go to avoiding contact with others. The one aspect that often is overlooked is the impact the pandemic has had on rodents, as these pesky pests are having to adapt like everyone else

How To Get Rid Of Rats

Rats can be a nuisance for any homeowner to deal with. As these pests can transmit diseases and can even cause damage to your home and property, thereby compromising the structure and potentially even creating possible fire hazards. Don’t worry, as Orkin Canada is here to help. Using our extensive experience, we’ve put together a list of the six most effective ways to get rid of rats in your home.

Remove pests from your home, and stop them from coming back

We work hard to listen, understand and assess your unique situation. Request a free, no-obligation estimate today for a customized pest program that fits your needs.

Request a Free Home Estimate
Request a Free Business Consultation