There are more than one species of fly, including house flies, phorid flies and even blow flies, that may be associated with sewers and called a sewer fly. Another possible candidate would be drain or moth flies, which may be found in many drains, bathroom pipes and other moist plumbing areas where organic material collects. Sewer flies are small flies that resemble moths. In small numbers, they can be helpful in breaking down material that blocks drain pipes. However, sewer fly infestations grow rapidly, and serious infestations can create health hazards.
Sometimes referred to as moth flies, sewer flies have small, furry bodies and hairy wings. Adult sewer flies can live up to a month. They have a rapid reproduction cycle and infestations are fairly common.
After a female moth or sewer fly lays her eggs in a moist, nutrient-rich environment, small larvae emerge in the form of pale maggots. Sewer fly larvae are surprisingly resilient and have been known to survive dramatic shifts in temperature. These larvae are also capable of surviving in very low-oxygen environments. Sewer flies pupate near their larval nesting places, from which they emerge as fully grown adults. Wings develop during pupation.
If you're combating a sewer fly infestation, begin by eliminating their breeding sites. Clean suspected drains with a commercial drain cleaner, and scrub the drain pipe vigorously with a long-handled brush. After their breeding sites have been eliminated, the reproductive cycle is disturbed. If you experience difficulty ridding your home of adult sewer flies, contact your local pest control professional.