Cosmetopus dentimanus
Adults resemble Chaetosa punctipes in being small, grey and pale legged, but the single sternopleural bristle, lack of pointed tip to the third antennal segment and presence of a bright orange frontal stripe should serve to distinguish it. The male front legs are distinctive with a swelling on the underside of the femora that fits into a series of depressions on the tibia. Anderson (1974)[1] reviews the Northern European members of this genus which all have similar modifications to the front legs. Wing length: ♂ 4.7 - 5.0 - 5.2 mm (2); ♀ 4.4 - 4.6 - 5.0 mm (4).
References
This species was added to the British list by Chandler and Stubbs (1974[1], 1975[2]) on the basis of a series of specimens taken on the banks of the River Test, Hampshire in 1970, 1971, 1974, 1975, 1986 and 1994 from late June to early July. The flies were swept from long vegetation and the foliage of riverside trees beside the small calcareous river running through fen and carr. In 1995 Martin Drake found a further specimen beside the River Itchen only a few kilometres away. This was swept from vegetation bordering ditches in an old water meadow (Drake & Ball, 1996[3]). It was found on the River Monnow in south Wales during a Dipterists field meeting in 1997 and again, relatively nearby on the River Usk, in 2011.
World distribution: Palaearctic: Czech Republic, Finland, Germany, Norway, Sweden, Switzerland; Russia: northern European regions.
References
- A species of the boreal genus Cosmetopus Becker (Dipt., Scathophagidae) new to the British Iseles, taken by the River Test in Hampshire. Entomologist's Record and Journal of Variation, 86, pp.154-158., 1974.
- A further note on Cosmetopus dentimanus Zetterstedt (Diptera: Scatophagidae). Entomologist's Record and Journal of Variation, 87, pp. 147-148., 1975.
- The second British record of Cosmetopus dentimanus (Diptera, Scathophagidae). Dipterists Digest (Second Series), 2, p.71., 1996.