Marsh flies

Overview

Dictya is a genus of marsh flies. It occurs in Scandinavia, the United Kingdom, North America, and Central America. There are at least 44 species of Dictya worldwide, 27 species in North America north of Mexico, and at least 4 species in Minnesota. They are common in late summer and fall in Minnesota, at least at Cedar Creek Ecosystem Science Reserve in Anoka County. Adults are found in marshy areas near ponds and streams and in moist woodlands. Larvae are aquatic and feed on snails, snail eggs, and slugs.

Description

Dictya are small to medium-sized flies, 3 ⁄16″ to ½″ (5 to 8 mm) long. The face is white with a small black spot in the middle. The antennae are distinctly projected forward. The body is usually yellowish-brown. The plate on the underside of the first thoracic segment (prosternum) is bare, not hairy. The wings are dark with numerous white spots, including two spots near the tip if the subcostal (Sc) cell. The legs are somewhat elongated but not especially long. On the male the third segment (femur) of the middle leg has a row of short, stout bristles on the underside of the lower (distal) half (posteroventral).

Identification beyond the genus level cannot be reliably made from photographs alone. For the species, identification requires microscopic examination of the genitalia.