There are thousands of winged insect species in the Diptera order, all of which have one set of wings, as opposed to the two sets of wings possessed by most airborne insects, including butterflies, dragonflies, bees, and wasps. Insects with one set of wings include mosquitoes, gnats, and flies. Many fly species that are considered indoor pests are known as filth flies due to their habit of breeding on decaying organic materials, such as dead plant matter, dead animals, excrement, rotting food and garbage. Filth flies acquire numerous disease-causing pathogens from these breeding sources, which, just like cockroaches, makes flies a potential disease threat.

Within homes, filth flies spread pathogens on food and countertops, and some species, like face flies, spread pathogens on human membranes in the eyes, nose and mouth, resulting in disease transmission, most commonly conjunctivitis (pink eye). Most filth fly infestation cases see the pests reproduce outdoors in close proximity to homes, but they frequently breed indoors as well. For example, phorid flies, drain flies, fruit flies and other common filth flies reproduce in kitchen areas where food and spilled liquids accumulate, such as between tiles, beneath appliances, and in corners, especially where flooring meets the bottom of cabinets.

Since fly eggs and larvae are extremely small at 1 or 2 mm in length, they can develop on very small amounts of rotting organic material. Even areas that appear clean can contain small bits of filth that can support fly development. Sometimes, a gelatinous material develops on areas of filth due to moisture, and this is exactly what female egg-laying flies find most attractive as breeding sites. Because of this, moisture is also important for fly development, and it is not uncommon for fly eggs and larvae to dessicate if moisture content in the surrounding environment is not sufficient. Keeping kitchens well sanitized and controlling indoor moisture will make homes inhospitable to flies looking to breed.

Have you ever experienced a fly infestation that involved indoor breeding?