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How To Control Cluster Flies

When there are flies around, you may not be too concerned with what type of fly they are; you just want them gone! Such is the case with cluster flies which are often mistaken to be house flies since they are similar in size.

Cluster flies are a smaller type of fly which reaches about 3⁄8-inch long. They are colored a dark, non-metallic gray with light and dark markings on their abdomens. When resting, the wingtips of a cluster fly overlap over one another. When cluster flies land on a surface, they leave behind a greasy spot.

What separates the cluster fly from a regular house fly is that cluster flies tend to fly much slower, making them somewhat easy to swat with a newspaper or fly swatter. However, much like their name indicates, cluster flies tend to hover around in large groups and can make for an unpleasant home infestation.

Cluster flies mainly like to live outdoors and feed on nectar from flowers and earthworms as well as breed on the ground. This is a stark contrast to other species of nuisance flies which like to associate themselves with filth and garbage to consume and breed around. Cluster flies can number anywhere to a few dozen to thousands which can definitely be a problem if they have made their way in your home.

During the fall and winter months, cluster flies seeking warmth will make their way inside of buildings and structures, usually via a crack or crevice which allows them entry. Flies are often “clustered” together in large groups and tend to reside in dark secluded areas like spare rooms, wall voids or in attics. They often are discovered when the weather becomes warmer and the flies, believing it to be Spring begin to fly out and appear around windows, alarming homeowners.

If you have a cluster fly invasion in your home, Solutions Pest and Lawn can help you by offering professional-grade DIY fly control products such as insecticides, dusts and traps which can get rid of cluster flies in no time flat.

Shop our variety of helpful and effective professional DIY products below and also learn how you can get rid of cluster flies easily via our step-by-step how-to instructions.

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How To Get Rid of Cluster Flies: 4 Step Solution

Getting rid of cluster flies may be frustrating but if you have the right products and helpful DIY tips at your disposal, you’ll have a much easier time eliminating cluster flies from your home.


Cluster flies are mainly an issue during the colder months when they infiltrate your home or when it is spring time and they come out of hibernation and emerge in search of a way to get outside. It can be disturbing to see cluster flies in their large swarms but there are some easy ways to get rid of them from your home or prevent them from entering your home to begin with. Check out our simple three step plan below and follow closely for best results.

Step 1: The best way to get rid of cluster flies is by preventing them from seeking out your home for residence in the first place. We recommend right before fall approaches to apply a preventative barrier treatment around your home. Equip yourself with a strong insecticide such as Reclaim IT. Mix the product in a gallon sprayer and apply outdoors to all window frames, door frames, soffits, eaves and the sunny side of the home as well as any other areas that are vulnerable to entry by cluster flies.  


As an addition, it would be wise to do some exclusion by applying caulk to any cracks and crevices that can serve as a point of entry for cluster flies (or any other insect) to come into your home.


Step 2:  Indoors, if cluster flies are already present in your home and there are large numbers of them there is a combination of things you can do to remove them from your home. Cluster flies are on the slower side and are not as evasive as other species of flies so they could easily be vacuumed up.


Another option is to use an aerosol spray such as Pyrid Aerosol as a space spray wherever you have found them. Spray the product inside the room and allow at least a half an hour for the room to ventilate before re-entering. When you come back in you should see a ton of cluster flies dead on the floor.


Step 3: If flies are located in wall voids or other hard to reach places, dusting can also be a viable option. Using a duster, apply a residual dust insecticide such as D-Fense Dust to any voids including underneath baseboards and behind electrical outlets and window and door frames. You some cases, you will need to drill a hole into a wall void, dust and reseal it to control cluster flies in those areas.


Step 4: Cluster flies are attracted to light so if they are hanging around your home, fly light traps can be an excellent way to take large numbers of them down. Install the fly lights in your attic or room where you suspect they are residing or hiding out. When the cluster flies emerge in the springtime, they will be lured by the fly lights and be stuck in the glue boards before they can travel to other places in the home.


By following these steps, you will successfully be about to get rid of cluster flies and they will no longer be an issue around your home.


cluster fly on a wallAll You Need To Know About Cluster Flies

Cluster flies(pollenia rudis) are a common fly which invades homes, particularly when temperatures are cooler in the late portion of fall to early spring time. A cluster fly is often confused to be house flies because of their similar appearance. However, the cluster fly is larger than a house fly and can be distinguished by hairs on the thorax which appear to be yellow.


Cluster Fly Biology

Cluster flies earn their name due to their tendency to travel closely together in large groups or “clusters”. They are known for traveling in the winter time to the sunny side of homes in those large clusters, flying up against windows trying to find a way in so they can have warm shelter.

 How to Identify Cluster Flies

Cluster flies are a part of the ‘Calliphoridae’ family of flies which is the same family of which blow flies and bottle flies belong to. While they are in the same family, cluster flies look very different in appearance to blow flies and bottle flies.


For one, cluster flies are bigger in size than house flies but smaller than bottle flies. House flies are between 8 to 10 millimeters long while bottle flies are between 10 to 14 millimeters. Cluster flies are darker colored than blow flies which are usually colored a bright metallic tone that is either greenish or bluish in hue. Cluster flies can also be distinguished by dark and light checkered pattern on their abdomen which look like splotches.


Another trait which can distinguish cluster flies and bottle flies is their movement speed. Bottle flies and the house fly are great flyers and can fly in quick controlled movements. Cluster flies on the other hands fly in a slow and sluggish kind of way, sort of like a mosquito.


When irritated or squished, the cluster fly gives off a faint but sweet odor which has been compared to smelling like buckwheat honey.


cluster fly close upCluster Fly Life Cycle

As opposed to most flies which like to breed and lay eggs in filth ridden areas or on top of food, cluster flies prefer to lay there eggs in the soil or on the ground. In the springtime, adult cluster flies breed their eggs where they know there will be earthworms around. Once the cluster flies hatch, they will readily eat the earthworms around them.


The most interesting thing about the cluster fly larvae eating earthworms is that they eat them from the inside out. Cluster fly larvae act as a parasite inside of earthworms which have consumed the cluster fly eggs. The eggs hatch inside of the earthworms who then literally eat their way out from the earthworm.


Around three to four generations of cluster flies are produced each season. The final generation is usually the generation which migrates indoors. Cluster flies would prefer to live and reside outdoors but when the temperatures drop and the time comes for overwintering, cluster flies are drawn to the warmth and shelter of a home or building.


Aside from man-made structures, cluster flies also choose to overwinter in places which have hedge rows, under the bark of dead or decaying trees; in the crevices of cliffs and rocks which face south. When these areas are not nearby, they will seek out staying in cracks, crevices and voids found in houses, garages, and other secluded areas where they can find warmth and stay tucked away for the winter.


The flies “cluster” together on the warm sides of buildings near the end of the summer season during the day. When the sun goes down and the temperatures cool, these flies crawl into the building through cracks under the eaves and around windows or through gaps in the siding. Once inside and safe in a secure are, cluster flies stay in hibernation until they feel the warmth of springtime and begin literally flying out of the wood works.


Once the cold winter temperatures have passed, cluster flies will move out of their state of dormancy and begin to move around in a slow, sluggish fashion as they search for a way out of the home via small openings around windows, moldings, and baseboards.


Cluster Fly Behavior

An interesting trait of cluster flies which you might notice if you look carefully is that when a cluster fly is at rest, their wings overlap on top of one another, unlike a house fly whose wings remain separate when they have stood still and are not flying. If you notice carefully a cluster fly at rest, you will see its wings overlap, whereas housefly’s wings remain separate during rest.


Unlike most flies, cluster flies are not attracted to filth, nor do they want human food so you shouldn’t expect cluster flies to come virtually out of nowhere at your next BBQ or when you have garbage that needs to be disposed of. Cluster flies mainly like to consume the nectar of flowers and earthworms.


Cluster flies have a longer lifespan than most other fly species. While the average fly may live less than 90 days, cluster flies have the capacity to live up to two years or longer. This is what makes them a particular nuisance to people. They tend to hibernate during the cold winter weather, choosing the warmth of man-made homes as their abode until the temperatures rise back up. They are not usually seen by us until the weather starts to warm up and they begin to get out from their secluded resting areas to try and exit from the home, shocking homeowners with their large numbers and annoying presence.


Homes which come down with a cluster fly infestation should be forewarned that their presence will not be a one-off occurrence. Cluster flies tend to gather around the same home they have chosen year after year, essentially “marking” it as a prime area for hibernation by releasing a pheromone which lends a signal to other cluster flies telling them that this is a great area to nest and stay warm from the cold.


The presence of the cluster flies may even go unnoticed for a couple of years, but with each year that passes, the cluster fly population will grow and once it gets big enough and winter turns to spring, they will make their presence known as they go flying about in attics and other largely undisturbed areas of the home.


What Damage To Cluster Flies Do?

Fortunately, cluster flies do not create any structural damage to homes which they invade, nor can they harm humans. They do not bite or sting and they do not have biting mouthparts like other flies do (horse flies, gnats etc). Cluster flies are mainly a nuisance with their presence in the home, especially when they have intruded upon the home is their large clusters.


At worst, these pests leave greasy remains when they land on the surface of an object or small dark-colored spots of feces on windows and walls, but they are not known to carry any hazard diseases detrimental to humans.


Because of the fact that cluster flies move slow and sluggishly, they can be easily swatted or vacuumed up. The death of cluster flies, especially when they are hiding in wall voids, can lead to infestations of larder beetles which will come to consume the dead cluster fly bodies.


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How To Manage or Prevent a Cluster Fly Infestationcluster fly ready to annoy

Cluster flies return annually so if you’ve experienced them in your home, it’s safe to say they will come back.


The best way to prevent cluster flies from seeking out your home is by implementing exclusion and preventative measures. One such way is by sealing up cracks and holes with caulk or by nailing pieces of wood around gaps and holes when clusters flies could use to gain entry into your home. This job starts in the summer or right before Fall in preparation for their potential arrival.


You should also be sure to have screens on your doors or windows and if you already do, make sure they are tightly secure and are not damaged in any way. If they are, replace or repair them.


It is also wise to use an insecticide to act as a barrier to keep cluster flies from getting into your home. An insecticide such as Reclaim IT or Martins Viper Insecticide Concentrate can work greatly to repel and kill cluster flies before they can successfully get inside. The moment they land on a surface that has been treated with one of these insecticides, they will fall dead.


Spray the product on the southern and western exterior sides of your home since this is where the sun shines and where they often gather in clusters around windows and siding to rest or keep warm.


What to Do if Cluster Flies Are Already Inside Your Home

If cluster flies are in your home among the best methods of control are vacuuming, aerosol spray control or UV fly light traps.


Using Aerosol Sprays

Spraying cluster flies with an aerosol spray is a great way to control their infestation. Since cluster flies hover together in large groups, this provides a large knockdown of a whole lot of bugs as opposed to flies that are scattered around and flying separately.


According to research from scientists, indoor pyrethrin based sprays are excellent methods of killing exposed cluster flies who have infiltrated a home during the winter and spring months. The added bonus is that pyrethrin aerosol sprays are safe to use because they are made with natural plant extracts that are safe to be used indoors and are overall environmentally friendly.


Solutions Pest & Lawn has a variety of pyrethrin aerosol sprays in stock and among the best ones to use to get rid of cluster flies is Pyrid Aerosol and CB-80 Insecticide Aerosol. The great thing about these products is that they can take care a lot more than cluster flies. You can use these products for a large number of common household pests.


When spraying make sure you let the room or attic where you sprayed ventilate for at least a half an hour before re-entering. You’ll notice a lot of dead flies upon your return. Make sure to sweep up and clean the dead cluster fly bodies as they may attract carpet beetles and other predatory insects if they are left unswept.


Using Vacuums


Because of a cluster flies slow and sluggish behavior, they can easily be caught and sucked up via vacuum. Any average mini vacuum will do. Make sure you use a vacuum that is lightweight, portable and has adequate sucking power. Please make sure to clean your vacuum after use, otherwise, cluster flies can release a musty odor inside the vacuum bag.


Using Fly Light Traps

If cluster flies are hanging around your attic or another room you rarely go into, placing a UV fly light trap can work wonders to capture those pesky flies. Cluster flies like most flies are attracted to lights. We have a number of different fly light traps in stock that work excellently such as the ones made from Mantis (Mantis Flylight 1x2) and Genus (Genus Spectra Compact Flylight) among others.


These bright and portable light traps consist of a small but high intensity lamp which shines UV light and contain adhesive glue boards to capture unsuspecting flies. Cluster flies are drawn to the allure of the UV Light and as soon as they come close enough to the lamp, they are trapped on the glue boards.


The glue boards are replaceable and can be replaced after few days or months. Solutions Pest & Lawn also has replacement glue boards your can purchase. Such fly traps consume up to 30 watts of energy and are effective in areas between 600-800 square feet.


Equip Yourself With Cluster Fly Control Products Today!

Solutions Pest & Lawn is dedicated to delivering you not only the best products to get rid of cluster flies and do DIY pest control, we also are dedicated to providing detailed free advice to help you comfortably and confidently carry out DIY pest control programs.


Browse our extensive knowledge base for articles and guides on how to get rid of flies and other problem pests around the home. You can also get live DIY help by calling us at 800-479-6583, live chatting with us on the Solutionsstores.com website or by emailing us at askapro@solutionsstores.com.


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Ready to put a stop to the cluster fly invasion? Click the button below to start shopping and equip yourself with the best cluster fly killer products.



Check out our Infographic on Overwintering Pests!

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