House Flies Indoors?

By Chris Williams on August 29, 2011.

Q. We’ve been having a real problem with house flies inside our house! I know that they are found around garbage and dog poop outside, but where are they coming from inside? I keep a tight lid on my kitchen garbage can and we actually see them mostly in the dining room near the windows. Can you tell me where they’re breeding?

flyA. I can maybe give you some clues as to where to look for evidence of fly breeding indoors. You’re right, house flies indoors are usually traced to outdoor problems like overflowing dumpsters. But occasionally the breeding site is indoors instead. First you need to know that house flies are attracted to anything moist and decaying for egg laying. The breeding source can be either vegetable or animal matter. If you find immature stages of the fly (larvae or pupae) inside, you know the breeding source is inside since larvae and pupae can’t fly and don’t travel far from their food source.

House fly maggots (larvae) are whitish, wormlike, legless, and appear to be headless. They are about 1/4 inch long. Fly larvae are usually found wriggling around directly in the material that they are feeding on. When they are fully grown, the larvae wander away from the food material looking for a drier place to pupate. The pupal case of the house fly looks like an oval brown seed, about 1/4 inch long.

Below are some possible indoor house fly breeding sites. Check these places for evidence of house fly maggots:


·        Rodent, bird, bat, or other animal carcasses – Dead animals in wall or ceiling voids, A/C units, crawlspaces, attics and other storage spaces could be the source of flies.


·        Rotting garbage in the bottom of garbage cans or forgotten garbage bags left in strange places like the garage. Check under the plastic liner in garbage cans.


·        Rotting fruits or vegetables – Dig to the bottom of the vegetable bin. New produce is often dumped on top of old produce which then rots unseen in the bottom.


·        Trash compactors – Look for overlooked food spillage underneath compactors and an accumulation of crud in the bottom of the compactor.


·        Kitchen equipment – Wet food debris can accumulate behind and under dishwashers or stoves. Check for a scummy drip pan under the refrigerator.


·        Animal feces – It may be unusual, but you can find feces from raccoons or other animals inside attics, crawlspaces, or garages. Bird or bat droppings could be accumulating in the attic.

If you can’t find the source of the flies, give Colonial a call. Our pest control technicians will conduct a thorough inspection. After the source of the flies is found, we remove the breeding material, clean up the site, and help you correct the conditions that allowed the decaying material (or animal carcass) to accumulate in the first place. If mice or even larger animals have moved into your home, we can set up a pest management program for those pests as well. We deal with pests so you don’t have to!



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