Female adult flies deposit their eggs on sources of decaying organic matter, such as excrement, rotting food, garbage, plant matter, carrion and compost. In order to obtain the nutrition they need to mature properly, larvae (maggots) consume this decaying organic matter immediately upon hatching. Due to their filthy reproductive habits, flies acquire a plethora of disease-causing microorganisms which they regularly smear onto foods and surfaces within homes, putting humans at risk of becoming ill. Thousands of fly species belonging to the Diptera order have been documented worldwide, but the species that reproduce in microbe-rich decaying matter are aptly known as “filth flies.”

Generally, each filth fly species favors a particular source of rotting organic matter. For example, house flies prefer to lay eggs on feces or on rotting food in garbage receptacles, while blow flies prefer to lay eggs on carrion. Fruit flies prefer to lay eggs on freshly decaying fruits in kitchens, supermarkets and on crops, while vinegar flies prefer to lay eggs heavily decayed fruit found caked onto garbage bins. However, adult phorid flies are unique for breeding on a wide variety of organic matter sources, including food buildup in drains, carrion, rotting vegetation, organic components in consumer products, contaminated soil, excrement and drain lines.

Phorid flies can breed on many sources of organic matter that vary in terms of decay. For example, a phorid fly infestation was once traced back to a bucket of organic glue within a bookbinding factory, while another infestation was traced back to wet flour in a bakery. The most common phorid fly breeding sites within homes include dirty trash and recycle bins, scum in drains and garbage disposals, and food caked in between floor tiles and beneath appliances. It is also common for phorid fly pests to invade homes from beneath foundation slabs where drain lines have become broken. When this occurs, phorid fly infestations will persist unless contaminated soil is replaced with fresh soil. Large numbers of indoor phorid flies may also originate from wet materials located within wall voids, and this is particularly common when plumbing leaks occur in wall voids where several dead rodent pests have collected.

Have you ever struggled to pinpoint the breeding source of fly pests that had infested your home?