Introduction: These flies get the common name of moth fly from their fuzzy appearance their bodies and wings being very hairy. The drain/filter/sewage fly common names are from places or situations which represent typical breeding and developmental sites. Although usually thought of as nuisance pests there have been cases where inhalation of their body parts caused bronchial asthma. Moth flies are found throughout the United States and most of the world.
Recognition: Adults about 1/16"-1/4" (1.5-5mm) long delicate and fuzzy. Color pale yellowish to brownish gray to blackish depending on the species. Antennae 12- to 16- segmented each segment bulbous and with a whorl of long setae (hairs).
Habits: Because of their small size moth flies are able to penetrate ordinary screens. Moth flies are weak fliers so indoors they are usually seen crawling on walls or other surfaces. When they do fly it is only for short distances of a few feet and their flight is in characteristic short jerky lines. During the day they typically rest on vertical surfaces near openings indoors and in shaded areas outside. Their greatest activity is in the evening when they can be seen flying or hovering above drain openings indoors and sewage filter beds etc. outside.