Sewer fly (Clogmia albipunctata) abdomen, coloured scanning electron micrograph (SEM). The sewer fly is known by various names including moth fly, drain fly, sink fly, filter fly and sewer gnat. Although a true fly of the Diptera order, their hairy bodies and wings give them a moth-like appearance. They are harmless but can sometimes be a pest due to their inhabitancy of drain and sewage systems. This image shows part of the abdomen and wings displaying an abundance of hairs.