Trichopalpus fraternus
An unremarkable small greyish species with dark femora (narrowly yellow at the base and tip) which otherwise resembles Chaetosa punctipes (which has pale legs) in size and shape. Thorax and abdomen densely grey dusted. Front of frons and sides of the face with reddish ground colour. Palps, small and brown. Wing length: ♂ 4.5 - 4.5 - 4.5 mm (2); ♀ 5.1 - 5.3 - 5.4 mm (2).
Larvae and pupae have been found associated with the nests of Coot (Nelson, 1995[1]), but this may simply represent a heap of wet, rotting vegetation and the fact that it is a birds nest may not be significant. Cole (1997)[2] also reports finding it in great abundance ("many hundreds") on a pile of rotting water plants (mainly the fleshy rootstocks of Yellow water lily Nuphar lutea) which had been pulled out of a Cambridgeshire gravel pit by fishermen and left piled up on the bank.
References
Probably not as uncommon as earlier literature suggests. Recent records suggest that it is widespread and that adults can be swept from long, damp grassland. Speight (1983)[1] confirms its presence in Ireland.
World distribution: Palaearctic: Belgium, Czech Republic, Denmark, Finland, France, Germany, Hungary, Ireland, Lithuania, Netherlands, Norway, Poland, Slovakia, Sweden, Switzerland; Russia: north European region.