Phoridae

The Phoridae are a family of small, hump-backed flies resembling fruit flies. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking to the wing. This behaviour is a source of one of their alternate names, scuttle fly. Another vernacular name, coffin fly, refers to Conicera tibialis. About 4,000 species are known in 230 genera. The most well-known species is cosmopolitan Megaselia scalaris. At 0.4 mm in length, the world's smallest fly is the phorid Euryplatea nanaknihali. For terms see Morphology of Diptera Phorid flies are minute or small – 0.5–6 mm (– in) in length. When viewed from the side, a pronounced hump to the thorax is seen. Their colours range from usually black or brown to more rarely yellow, orange, pale grey, and pale white. The head is usually rounded and in some species narrowed towards the vertex. The vertex is flat. In some species, the ocellar callus is swollen and highly raised above the surface of the vertex. The eyes are dichoptic in both males and females (eyes of males close-set, of females wide-set). The third segment of the antenna is large and rounded or elongated, and bears a long apical or dorsal arista directed sideways. The arista is glabrous or feathered. The third antennal segment in some species is unique in shape. Sexual dimorphism is often shown in the shape and size of third segment of antennae, and in males, the antennae are usually longer. The proboscis is usually short and sometimes with enlarged labella. The proboscis may be elongated, highly sclerotized, and bent at an angle. Maxillary palpi vary in shape and are sometimes large (species of genus Triphleba). The groups of bristles are developed on the head. Two pairs of supra-antenna1 bristles, sometimes one, are completely reduced. Above these are antenna1 bristles closer to (but still some distance from) the margin of eyes. Three bristles are spaced along the margin of eyes-anterolateral midlateral and posterolateral. Immediately before the ocellar callus are two preocellar bristles.