Microprosopa pallidicauda
Face frons and jowls yellow and contrasting strongly with the dark grey dusted orbits. Occiput grey dusted. Proboscis shining black. Antennae small and dark. Palps strongly widened, globular and mainly yellow. Legs entirely yellow. Anterior wing veins yellow, darkening towards the apex and posterior margin. Wing length: ♂ 3.5 - 4.1 - 4.7 mm (52); ♀ 3.7 - 4.3 - 4.8 mm (10).
Found near water where it is associated with Scirpus and Carex species. It is believed to belong to the group of species with predatory aquatic larvae. Adults fly in June and July.
Similar in size and general appearance to Chaetosa punctipes which is also abundant in the areas along the River Spey where M. pallidicauda is found and the two may be found side by side in the same sample. Whilst the black antennae of Microprosopa are a useful feature, the colour of the antennae of Chaetosa is quite variable and individuals with darker third antennal segments occur. However, Chaetosa has obvious, strong anterior-dorsal bristles on the front femur whereas the front legs of Microprosopa are devoid of any obvious bristles (the rows of tiny black bristles along the ventral side of the front tibia of Microprosopa are not easy to see and require careful positioning under high magnification and good lighting). These leg bristles on Chaetosa are quite obvious when sorting a sample under fairly low magnification and may be visible on a decent photo, depending on the angle.
British records appear to be confined to the Spey valley where it is locally abundant along the river from Insh to Grantown. Speight (1983)[1] records it from Ireland. Hackman (1956)[2] regards it as a high-boreal and boreo-alpine species. Also occurs in North America (Vockeroth, 1987)[3].
World distribution: Palaearctic: Czech Republic, Finland, Ireland, Norway, Poland, Slovakia, Sweden, Switzerland; Russia: European and eastern Palaearctic; Nearctic: Canada, USA (Alaska).
References
- , 1983. Cordilura aemula and Microprosopa pallidicauda new to Ireland, Trichopalpus fraternus confirmed as an Irish insect and other Irish records of Scathophagidae (Diptera). Irish Naturalists Journal, 21, pp.165-167.
- , 1956. The Scatophagidae (Dipt.) of Eastern Fennoscandia,. Fauna Fennica, 2, pp.1-65.
- , 1987. Scathophagidae. Agriculture Canada Monographs, 28, pp.1085-1097.