Dung flies are small to minute, usually dull-colored flies with characteristically thickened first tarsomere of the posterior leg. The first tarsal segment is less than times as long as the second tarsal segment and dilated. The crossvein separating the second basal and discal cells is missing. Veins four and five often fade apically. They occur all over the world except in regions with permanent ice-cover. Despite their ubiquity and abundance, little is known about their economic or ecological impact. Some species are known to be parthenogenetic.