For terms see Morphology of Diptera 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. Larval stages are poorly known, but those described are slender, narrowed anteriorly, with groups of ventral spicules on creeping welts. The larva is amphipneustic. The mandibles are simple, hooked, and without additional teeth. The parastomal bars are long, thin structures, fused to the tentoropharyngeal sclerite. The hypopharyngeal sclerites are long separate or connected by a sclerotized bridge; the anterior spiracle is a rosette or branched. The posterior spiracles are usually on two cylindrical lobes. Each spiracle has three slit or oval openings and three or five groups of interspiracular hairs that are branched in some species. The larvae are microbial grazers found in abundance in many microenvironments with decomposing organic material. Most species appear to be associated with decaying plants or fungi and they are a part of the nutrient cycle. Some species, especially cave species, are polysaprophagous. Many species are associated with various kinds of faeces including human faeces; there are a few carrion-feeding species. These, however, are extremely abundant and are important components of the carrion-insect community. Sphaerocerids that abound in economically important decomposer communities such as compost and manure, and some decay cycles such as the wrack cycle are mediated by sphaerocerid-dominated insect communities. As their microbe-associated habits suggest, sphaerocerids may carry many pathogenic microorganisms. Although their reclusive habits preclude a major role in disease transmission; some can present a public health hazard on occasion or act as a warning of one. For instance Leptocera caenosa and other sphaerocerids are associated with blocked sewage drains. Some species occasionally reach high population levels in food-processing plants and other buildings where they may indicate blocked drains, waste accumulation and inadequate hygiene. One species, Poecilosomella angulata, has been implicated in human intestinalmyiasis They have been implicated as the major means by which nematodes are disseminated among mushroom houses. Sphaeoceridae often coexist with muscoids especially Fannia canicularis and Musca domestica in the complex manure ecosystem of poultry houses, and other confined-animal facilities. Here the sphaeocerids are prey for mites and beetles, which themselves also feed on the immatures of muscoid flies reducing the population of the more problematic muscoids. Carrion-feeding species are useful post mortem intervalindicators in forensic entomology.
Genera
The genera are arranged alphabetically according to subfamily; these are arranged in the presumed phylogenetic sequence from the most ancestral to the most advanced: Subfamily Tucminae Marshall, 1996 Subfamily CopromyzinaeStenhammar, 1855 Subfamily SphaerocerinaeMacquart, 1835 Subfamily Homalomitrinae Roháček & Marshall, 1998 '' of the Limosininae Subfamily Limosininae Frey, 1921
