Sewer gnats, also known as drain flies, moth flies and filter flies, are fuzzy members of the Psychodidae family of winged insects. They have one pair of wings, are dark gray or black in color and are commonly found near tubs and sinks.
Adult drain flies grow up to 1/5 of an inch and are covered in dense, dark and thick hairs. Female drain flies lay eggs that hatch into larvae that have pale centers and dark ends. The larvae consume algae, fungi and bacteria and thrive in liquid or slime that builds up in still water, drains and sewage treatment beds.