House fly Question

Why would I have house flies inside my house? I know they’re associated with garbage, but the kitchen garbage can is covered and I take the garbage out regularly. I see them mostly in the upstairs bedrooms, sometimes several each day.—T. Y., Chichester, NH

Answer

You sound like a candidate for a professional pest control inspection. There are several possibilities. The first thing is to make sure that we are actually dealing with house flies. There are similar looking flies, like cluster flies, that come from different sources.

There Could Be an Outside Fly Source

First, I would check to see whether you have a fly breeding site outside in your yard, something like dog feces, a dead animal, or rotting fruit. The source could even be in your neighbor’s yard, or maybe you live next to a farm with animals (and manure). Then I would check your screens and the tightness of your doors and windows and ask you if you leave them open during the day. Flies could be entering your home from outside.

Another possibility is that the flies are actually breeding in your home. After ruling out the more obvious sources of indoor house flies like spilled garbage in a hidden place, rotting vegetables in a bin, overlooked pet poop, we would have to consider whether there might be an animal carcass in wall or ceiling voids, or in the attic or crawlspace. Flies that are developing from maggots feeding on a hidden carcass could be emerging into the living space while looking for a way outside.

Follow Your Nose to Find the Maggots!

If the source of your flies is a dead animal, you should have been able to smell it, at least to some degree. But by the time flies emerge from a carcass, the odor may be largely gone. The dead carcass could be a mouse (especially if you’ve been having mouse problems and have been using rodent bait), or a rat, or something larger like a dead bird, squirrel, or raccoon. The amount of odor, the number of flies, and the length of time that you have been seeing flies are all clues as to the size of the dead animal.

If the flies are coming from a carcass, the problem may resolve itself eventually. As the carcass is depleted by feeding maggots and dries out, fewer flies will be able to emerge. If we can determine the location of the carcass, we can remove it and treat the area both for odor and for remaining pests. In your case, seeing most of the flies upstairs could mean that the source of the problem is in the attic, or the flies could be flying to upstairs lights.

You shouldn’t have house flies inside your home. They carry germs and can spread disease. Give Colonial a call today and let one of our experts do a thorough inspection. It’s always best to find and correct the source of a pest problem, but if we can’t find the source, we can still eliminate the flies that are in your home to give you relief.