Filter flies are small, winged flies with hairy bodies. They are nocturnal creatures, and they like to dwell in damp places. You can often see them in bathrooms and sewage disposal plants. Their larvae (which are brownish and cream-coloured) are usually placed in aquatic areas, such as the bathroom sinks.
Do not let their harmless appearances fool you as they can also be a health hazard to human beings. These filter flies are capable of transmitting various tropical diseases.