They're a nuisance. Several species of flies regularly invade and infest houses. Some, such as the house fly, fruit fly, moth fly, blow fly and phorid fly, can multiply and spend their entire life cycle in a home. Opportunistic flies, such as the cluster fly, face fly, fungus gnat, stable fly and flesh fly occupy the house through an open door or window but don't spend their entire life cycle within the home.
Stable flies and face flies invade houses located near livestock or horses. The pests occur around manure and decaying grass. Stable flies have the ability to deliver a painful bite to humans and animals. These insect pests readily feed off the blood of both humans and animals. The flying insects often invade houses during the peak feeding hours in the morning and afternoon. Flesh flies breed and feed outside, but can sneak indoors. They swarm around decaying animal flesh. The insects also frequent trash bins.
Cluster flies seek refuge inside houses, especially in attics, during the winter months. The warmth of the home makes the flies active, and they often swarm into living areas. Face flies invade the house in the fall to seek protection from the cold weather. They usually occur only around homes located near livestock. Phorid fly often occur around moist houseplants or in rotting fruit, where they breed. The common house fly also spends its life indoors, where it breeds and feeds on garbage or rotting fruit. The blow fly will breed within rotting meat kept in garbage cans. The filter beds of local sewage treatment plants can blow the moth fly through drainpipes into homes. Fruit flies can also come through drainpipes or appear in rotting fruit.
Maintaining sanitary conditions in and around the home can help prevent flies from occurring in the house. Keep all manure picked up. Promptly remove garbage from indoors and keep outdoor garbage sealed in cans. Homes with livestock should always keep the manure picked up, and locate any compost piles away from the house. Consider keeping the compost pile covered with black plastic to reduce fly numbers. Remove any rotting fruit from beneath fruit trees to keep flies away. Avoid over-watering houseplants. Make sure all windows have tight-fitting screens and all external cracks have been caulked. Applying weather-stripping around doors will also help keep flies out of the home.
Sticky resin traps will attract and trap flies that gain admittance into the home. Indoor light traps will help control flies that swarm during the evening or night hours. A fly swatter can effectively control a mild infestation of flies. Synergized pyrethrins sprays or aerosols can also efficiently kill flies indoors. Follow the directions on the label for application. Avoid using the insecticides in the kitchen or in any other food-preparation area. Consider placing commercial fly baits in garbage cans or other areas that the flies frequent.