; order Diptera, suborder Nematocera)
Family of minute flies which is regarded by some authors as a subfamily of Mycetophilidae. These may be recognized by their characteristic wing venation, with prominent anterior veins, and simple, fine, posterior veins. The compound eyes curve to meet one another above the antennae. Some species are sexually dimorphic, the females being normal but the males having greatly reduced wings. The larvae often move en masse, a phenomenon that gives them their common name. More than 1200 species have been described.
Subjects: Zoology and Animal Sciences.