There are around 150,000 Diptera fly species that have been documented, and experts estimate that there could be as many as one million Diptera fly species in the world today. Many Diptera fly species are categorized as nuisance pest species that can indirectly spread a number of diseases to humans. This is especially true when it comes to filth flies that make contact with feces and garbage, as these fly species can transport disease-causing pathogens to human skin and human foods. One of the most disgusting species of Diptera fly is the moth fly, or the drain fly as it is also commonly known. The drain fly gravitates toward feces, making sewers a popular hangout for these flies. This preferred dwelling space explains why these flies are often referred to as sewer flies. It is not uncommon for drain flies to emerge within homes through drains and they have even been found within toilets. Much like other nuisance fly species, like fruit flies and fungus gnats, drain flies can reproduce indoors where they can remain indefinitely. Drain flies are distributed in every region of the United States, but they are particularly numerous in Louisiana and other Gulf Coast states where the humid and wet weather provide the flies with ideal living conditions.

Drain flies can be discerned from other Diptera fly species by their small size, weak flying ability and greyish-black fuzzy exterior. Infestations are usually first noticed by their presence near sinks and tubs within bathrooms and kitchens. Drain fly infestations can become a nuisance in a relatively short amount of time, as both mated and unmated females lay between 30 and 100 eggs that hatch within a 48 hour period. Females lay their eggs on the slimy gunk that forms around drains, septic tanks and sewage filters. During maturation, the larvae and pupae feed on the fungi and bacteria that grow on this gunk. A newly hatched larva will become an adult drain fly after around 25 days of development. Drain flies cannot survive without high moisture conditions, so reducing moisture levels at the source of their breeding site can help to eradicate the pests.

Have you ever found a fly emerge from a drain?