Diostracus Loew, 1861

Grichanov, Igor Ya., 2013, West Palaearctic species of the genus Diostracus Loew, 1861 (Diptera: Dolichopodidae), European Journal of Taxonomy 61, pp. 1-14 : 2

Genus Diostracus Loew, 1861

Diagnosis

The genus is very polymorphic and characterized by the following combination of characters: body dark and stout, medium- to large-sized; palpus usually enlarged, loosely applied on proboscis; proboscis bulky; antennal scape glabrous or setose dorsally; arista-like stylus usually dorsal, sometimes basodorsal or subapical to apical; posterior mesonotum flattened; acrostichal setae absent; 4–6 dorsocentral bristles variable in length; sutural and postsutural, some notopleural, supra-alar and post-alar bristles sometimes absent or reduced; scutellum with 1–2 pairs of strong bristles and with some short lateral setae or hairs, sometimes with three pairs of long bristles; mid and hind coxae without bristle on the outer side; legs often modified; tarsi with more or less modified empodium and claws, usually without pulvilli; wing elongate and wide, sometimes modified in males; costa ended beyond tip of wing; crossvein dm-cu longer than distal section of CuA 1 vein, sometimes strongly sinuate; M 1+2 usually slightly convex anteriorly, often irregularly curved, more or less parallel to R

4+5

, at least partly behind dm-cu.

Remarks

The genus Sphyrotarsus Mik, 1874 includes 5 species from the European Alps, one Caucasian species and one Pamiran species. It was diagnosed by scape glabrous dorsally; tarsi with reduced empodium and without pulvilli; M

1+2

and R

4+5

are not strictly parallel to each other ( Parent 1938); scutellum with 3 pairs of bristles ( Negrobov 1978). Furthermore, the Pamiran subgenus Takagia Negrobov, 1973 (of Sphyrotarsus ), was diagnosed by elongated antennal postpedicel with arista apical, somewhat widened at apex in male; sutural bristle absent; one supra-alar bristle; scutellum with 2 pairs of bristles ( Negrobov 1973, 1978). Nevertheless, all these characters are rather variable and can be found in East Asian species of Diostracus . The monotypic Caucasian genus Lagodechia Negrobov & Tsurikov, 1996 was diagnosed also by variable characters of face, mesonotal setation, wing venation and morphology of abdomen ( Negrobov & Tsurikov 1996). In addition, some characters of L. spinulifera were incorrectly described, as follows from the illustrations published by Grichanov et al. (2011a, b). I think the diagnostic characters of these taxa have low generic significance and regard Lagodechia , Sphyrotarsus and Takagia (now Ozmena Özdikmen, 2010 ) as subgenera of Diostracus . Accepting a new concept of the genus, I associate 97 species with Diostracus , of which 64 occur in the Oriental Region, 30 in the Palaearctic and 3 in the Nearctic Region. The flies of the genus are all torrenticolous in habitat.