Chrysotus Meigen

Wei, Lianmeng & Zhang, Lili, 2010, A taxonomic study on Chrysotus Meigen (Diptera: Dolichopodidae) from southwest China: descriptions of eleven new species belonging to the redefined C. laesus - group, Zootaxa 2683, pp. 1-22 : 2

Chrysotus Meigen

Chrysotus Meigen, 1824: 40 . Type species: Musca nigripes Fabricius.

Diagnosis. Generally, species of Chrysotus from Guizhou are readily recognized from other Dolichopodidae , although this genus lacks distinct features, especially MSSC. It can be distinguished from closely related genera Diaphorus Meigen and Asyndetus Loew , especially the former, by the following characters:

1. Male frons usually wider than face; male face usually hidden by contiguous eyes, infrequently narrowly or widely separated.

2. Upper part of proepisternum bare, lower part of which above fore coxa with black setulae and black setae; claws usually visible and not fused to enlarged pulvilli.

3. Costa reaching to tip of M1+2. R2+3 straight or slightly curved towards costa, never forwardly at end. R4+5 equally bent posteriorly, which usually runs parallel to M1+2 apically, seldom very slightly divergent or convergent apically.

4. Male sternite 8 usually without stronger setae than those on tergite 6, although some taxa with a pair of stick-like setae; lateral epandrial lobe usually short and wide, never prominent (without specific strap-like lobe, which lacks strong setae); ventral projection of epandrium indistinct; surstylus and cercus simple, not divided into two lobes; hypandrium seldom simple, usually with process at apex.

5. Body smaller, with thorax and abdomen never yellow; antennae usually black (only C. gratiosus Becher, 1922 from Oriental Region with reddish yellow antennae).

Remarks. The subfamily Diaphorinae consists of 18 genera (Yang et al. 2006), in which the two major genera, Diaphorus and Chrysotus are closely related and encompass more than 60% of all species in the subfamily ( Capellari & Amorim 2010). These two genera are poorly defined in relation to each other and also in relation to some other diaphorine genera ( Bickel 1996, 2005). It often becomes difficult to identify unequivocally the species of diaphorine genera, especially species of these two genera. Consequently it is a difficult task to provide the exact placement of species on the basis of correct definitions of genera in Diaphorinae . Even though the above-mentioned five items delimit Chrysotus , it should be emphasized that the careful examination of internal genitalic structural characters of both male and female terminalia, which were often neglected previously, is an important source of phylogenetic information ( Capellari & Amorim 2010).

Chrysotus , as treated in this paper, is large and poorly defined genus with worldwide distribution. In Guizhou Province, southwest China, more than 150 species (about half of known species of the world) have been identified from about 10,000 specimens. Sorting these species into distinct species-groups based mainly on specific characters of the male terminalia is part of on-going studies.

Habitat. Adults move about on grass and brushwood (never found on ground), especially about streams, pools and reservoirs, etc. Species of Chrysotus were collected with yellow pan traps in or nearby conifer and broadleaf forests, which are primary, secondary or artificial growth stands.

In Guizhou Province, species of Chrysotus were collected from 100 m to 1800 m, but species appear to be more easily found below 1500 m.