BRACHYCERA, Muscomorpha Schizophora Acalyptratae, Lauxanioidea
Number of British species: 32
Difficulty: 3-4 Panel
Minute to small (1-5 mm), usually silvery grey flies, in some cases with brown, grey or black markings on the head, thorax and abdomen. Arista bare to pubescent; ocelli present; Ocellar bristles present, in some cases curving backward, or absent. Postvertical bristles converging or reduced to absent; 0-3 pairs of frontal bristles, if present, curving backward; especially in the large genus Leucopis dorsal bristles of the head largely absent; scattered interfrontal setulae present; vibrissae present or absent, often a series of vibrissa-like bristles present. Wing unmarked, in some cases costal area darkened; costa continuous; vein Sc complete crossvein BM-Cu present; cell cup closed. Tibiae without dorsal preapical bristle.
The larvae prey on aphids, scale insects and their allies, e.g. gall-building Psyllidae. Some species have been artificially introduced as biological control agents against pest woolly aphids especially in coniferous forests. The adults are found especially in grassland habitats and near the larvae where flies of e.g. the genus Leucopis feed on honeydew. The adults of this genus are able to walk sideways and backwards with ease, probably an adaptation enabling them to avoid the ants trying to chase off or kill everything that comes near 'their' aphids.