Mothfly

These flies get the common name of mothfly from their fuzzy appearance, their bodies and wings being very hairy. The drain/filter/sewage fly, common names, are from places of situation, 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 are about 1/16-1/4 inch 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. Wings broadly oval, pointed apical, veins and margins hairy, and held rooflike over body at rest. Non-biting. In addition, ocelli absent and cross veins restricted to basal third of wing.

Mature larvae are about 1/8-3/8 inch long, eyeless and legless. Subcylindrical in form, with head narrower than body and terminal rear segment narrow, forming a short hardened breathing tube. All or some body segment narrows, forming a transverse, sclerotized, strap-like bands on their dorsum. Color pale with head, dorsal bands, and apical breathing tube dark.

Habits

Because of their small size, moth flies are able to penetrate ordinary screens. Moth flies are weak fliers, so indoors they usually are 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 drain 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 or sewage filter beds, etc. outside.