Flies in the Home

Learn how to prevent flies from infesting your home.
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Flies in the Home

Around the House

Houseflies are often called "filth flies," and for good reason. They chow down on nasty things -- garbage, manure, dead animals, and the like. These also serve as breeding and egg-laying sites.

Houseflies are such danged nasty pests that it's hard to believe that they are considered beneficial bugs in nature, but they are. As decomposers of dead and decaying vegetation and organisms, they perform a vital function. They're also an important part of the food chain, serving as a food source for birds, reptiles, fish, and even some kinds of plants.

Because flies often feed on filth, they can harm people and animals by spreading diseases such as dysentery or typhoid fever. They can also contaminate food and cause food poisoning and/or diarrhea. When feeding, some flies -- most notably stable flies and mosquitoes, which fall into the same order -- can also inflict painful bites.

Most flies prefer to spend their time outdoors, but a handful of species have found human structures preferable to living in the wild. There are two categories of these pests:

  • Household-infesting flies, which breed and complete their life cycles indoors when they can find favorable breeding spots.

  • Household-invading flies. These flies breed and develop outdoors, but come inside during certain times of the year.

Experts recommend identifying the species that is invading your home. Doing so is key to figuring out what's causing the infestation and helps pinpoint Integrated Pest Management (IPM) measures. This is a good idea and will put you in control faster, but simply following a good IPM plan will accomplish the same goals. It just might take a little longer.

A Fine Mess

Think a few flies aren't that big of a deal? Think again. One fly can carry more than 4 million bacteria on its body andover 28 million in its stomach.

Here's a quick description of the different categories and the species in each, just incase you do want to take the focused approach. The ones you're most likely to encounter lead off each list:

House-infesting flies:

  • Housefly. The most common fly pest around homes. They lay eggs on wet decaying organic matter, on animal manure, and in rotting plant debris.

  • Blow fly. Shiny, metallic flies. They lay their eggs on dead animal carcasses, decaying meat, and garbage that contains meat scraps. Called blow flies because their larvae develop inside dead animals, causing the carcasses to bloat.

  • Fruit fly. Tiny tan flies with red eyes. More of a problem during the fall, they reproduce and develop on overripe and rotting fruit, vegetables, and other moist plant material. They'll also feed in drains where organic debris has been allowed to accumulate.

  • Phorid fly. Very small fly that flies with its back legs hanging down. They like to lay eggs on rotting vegetables, fruit, or meat; potted plants; wet organic soil and cut flowers; and in garbage disposals and floor drains.

  • Drain fly. Also called moth, sewer, or filter flies. They breed in the organic material that can build up inside drainpipes. If you have flies in your bathroom, they're probably these.

House-invading flies:

  • Cluster fly. Not filth flies, but a common indoor pest. Dark gray flies, about the same size as blow flies. They're slow flyers and smell like honey when swatted. Adult flies over winter in the top floors or attics of homes, typically choosing the south- and west-facing walls where they can stay warm. On warm days they'll invade indoor spaces and collect en mass at windows, often in rooms that aren't used regularly.

  • Face fly. These flies resemble houseflies. They pester cattle during the summer and over winter in wall voids. Adults will emerge from attics and walls during warm days. They're typically more of a problem in rural areas, especially in homes near pastures or where cattle are kept.

  • Flesh fly. These flies are gray with black stripes. They feed on animal carcasses,compost piles, and garbage dumpsters.

  • Stable fly. Also called biting houseflies, they feed on the blood of warm-blooded animals, including humans. Their bite is painful, most often incurred around the ankles, and they'll even bite through clothing in their quest for blood. Adults lay eggs in decaying vegetation, including rotting straw, grass clippings, compost piles, and decaying fruit and vegetables.

  • Fungus gnat. These flies resemble tiny mosquitoes. They feed on fungi, which they find in over-watered plants and pigeon feces. Light attracts them, and they'll come inside at night through open doors and windows.