Large Black Flies Suddenly Appearing in Bathroom

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The sudden and mysterious appearance of black flies in your home and particularly in your bathroom can be dumbfounding and frustrating. Luckily, there are ways to fix this problem and eradicate the flies from your space.

Cluster Flies in Your Home

Cluster flies are a common occurrence in many homes. These are about the same size as regular house flies, but they fly more slowly. These flies are most likely to migrate into homes during the cooler seasons and they’ll typically appear suddenly in your home. These flies enter your home via small cracks and crevices as soon as colder weather starts to set in, usually in the fall.

black fly close up

Identifying Cluster Flies

Cluster flies look very similar to other large flies and can be tricky to identify. These flies have a black and silver checkered body. Young cluster flies can be identified by the short light-brown and yellowish hairs they boast on their lower bodies. Cluster flies also have overlapping wings when they are at rest.

These flies can also be identified by their sluggish movement. They are noticeably slower than regular house flies as they buzz around.

Finally, cluster flies usually congregate in groups - or “clusters” - near windows that receive sunlight. If you’re experiencing an abundance of these flies in your bathroom (or any other room in your home), it’s likely they’re near a window.

shower with black flies

How to Get Rid of Cluster Flies

There are several measures you can take to rid your home of cluster flies if they’ve taken residence in your bathroom or anywhere else in your home. First, because these flies are slow and sluggish, it’s usually easier to swat or vacuum them than it is normal house flies. However, since they usually appear in groups, it can be frustrating and time consuming to get rid of them all this way.

While pesticides are not the most reliable method of cluster fly removal, you can use it with some success. A professional application of an insecticide along the wall where they are most frequently clustering is usually effective.

cluster of dead black flies

Preventing Cluster Flies in Your Home

Especially if you’ve had cluster flies and worked to eradicate them from your home, you’ll probably want to work to prevent their return. The most effective way to do this is to caulk and fill all cracks around your home. This includes around doors and windows, under and along eaves and siding, around electrical outlets, at pipes, wires, and cable penetrations, surrounding vents, and along your roof. All doors and windows should be well-fitted and caulked or weather stripped as needed. Finally, window screens with holes should be repaired.

hands caulking window

Getting Rid of Regular House Flies

If you find that the flies you’re noticing in your home are not, in fact, cluster flies, you still want to get rid of the bugs that are residing within your house. There are several ways to do this. Start by simply practicing good sanitation in your home, as house flies are attracted to garbage and debris. This means eliminating food sources for flies - such as meat, garbage, and rotting vegetables. Empty garbage cans and clean your fridge and kitchen thoroughly. Do not leave dishes in the sink and ensure that your pantry is closed at all times.

Another method of getting rid of flies that happens to be natural is creating an apple cider vinegar trap. Fill a glass jar with apple cider vinegar accompanied by a few drops of dish soap. Place a funnel at the top of the jar. Flies will be attracted to the sweet smell of the vinegar and will enter the jar via the funnel. When they drink the solution, the soap will poison them and cause them to be trapped in the jar and easily disposed of.

Flies of any kind are certainly an unsettling issue to have in your home, particularly when they appear suddenly. Luckily, this is a fixable problem with a bit of effort and attention.