They are also called filter flies or drain flies. They get their name from their attraction to decaying matter in sewers and drain pipes. They are generally ¼ inches in size with, bodies and wings covered with gray long hair, which gives them have a fuzzy moth – like appearance. They are about 1/3 of the size of an average house fly. Their wings are normally held in a roof like manner above their bodies when they are at rest.
They breed in moist areas such as sinks and tubs, sewers or in places with lots of organic debris. They can also be found breeding in standing or stagnant pools of water. They normally enter homes through drain pipes in the kitchens, toilet sinks and bath tubs. Sewer flies feed on sweet liquids while larva feeds on any organic material in the slippery surface of areas they are found in.
The female lays about 30- 200 eggs, which hatch in 32- 48 hours, at room temperature. The life cycle is composed of eggs, larva, pupa and adult stages. Development through the cycle takes a maximum of three weeks, and adults live of a maximum of three weeks. The larva has a long thin tube at their rear end that they use for breathing, and a suction cup beneath their bodies to hold on to slippery surface in wet drains. Sewer flies can transfer bacteria from decaying matter from place to place. If unchecked they grow into a significant health risk.