These flies are really fuzzy and hairy hence another name for them – moth flies. When they are resting on a surface, their wings are set apart rather than folded over one another giving them a moth-like appearance in that aspect. They are gray in color and they do not fly very well. After mating, the female will find a place with decaying wet organic matter and lay anywhere from 30-100 eggs. They develop by complete metamorphosis. Once hatched, the larvae will begin feeding on the organic buildup around where they were hatched at. They then develop into the pupal stage and soon after that they emerge as adults. This development from egg to adult can take anywhere’s around 7-21 days depending on the conditions on where they’re at. With those numbers, populations of drain flies can take off quickly and grow in large numbers.
They are typically found breeding in filthy conditions but despite that – they’re not known to transmit diseases to humans. Once they get to the adult stage of their life – they only live an average two weeks which this time is used primarily to reproduce. They are prevalent in sewer lines, grease traps, wet buildup organic debris in shower drains, floor drains, under commercial kitchen equipment, and other similar places that have wet decaying organic debris. Due to their fast lifecycle, it is important to identify all potential breeding sites and remediating the wet organic debris by physically cleaning it up or out and by solving any moisture issues where possible.
Once this is done, a professional pest control tech would be able to treat those areas with an appropriately labeled residual pesticide to kill the adults. Products like BorActin insecticide powder works like a charm when flushed down the toilet to control populations within sewer lines. There are microbial cleaners that can be used on a regular schedule that will help inhibit organic debris from collecting after an area has been thoroughly cleaned of it. The one key factor in managing any fly issue is to thoroughly inspect the affected areas for the breeding source or sources. Remediating those breeding sites will provide long-term control. These small species of flies will sometimes find the most unusual places to breed so leave no stone unturned.