Hydrotaea hsiai Fan, 1965

Fig. 1 C–F

Hydrotaea hsiai Fan, 1965: 87 . Type locality: China, Qinghai prov., Haiyan distr. (= 37.0°N 100.8°E).

Descriptive notes: MALE (Fig. 1 D), body length 4.5–5.5 mm.

Head: Eyes bare. Fronto-orbital plates touching, distance between eyes equal to diameter of anterior ocellus. Fronto-orbital plates glossy black in anterior half. Fronto-orbital plates with 8–9 pairs short inclinate setae from lunula to middle of frons. Antenna black, arista virtually bare.

Thorax: Glossy black, without any dusting. Chaetotaxy: strong ac absent, ac hairs long, in 6 rows; 2+4 dc; katepisternals 1+1, katepimeron bare; notopleuron with hairs on area between notopleural setae. Lower katepisternum ahead of mid coxa with usual setae reduced, but with a pair of clusters of 3 long slightly back-curved setae.

Wing: Hyaline, calypters white, haltere with black knob.

Legs: Black; f1 with two typical ventral hooks at apex; t1 with pd seta in apical 1/4; f2 with about 10 strong and long pv setae (1.5– 2x as long as femur width), 5 more sparsely placed setae in basal half and a cluster of 5 more approximated setae in apical half, medially with a bare gap between the two clusters of setae; on av- surface with 5– 7 weaker setae in apical half; t2 with 2 p and elongated hairs on p surface; f3 with 4–5 long av in apical 1/3; t3 with 2 av, 1 short ad and 1 pd. Mid tarsus modified: tar2– 1 in basal half ventrally with a cluster of 4–5 elongated spinulose setulae and 6–7 fine curved hairs.

Abdomen: Entirely glossy black with blue shine.

FEMALE (Fig. 1 C) differs from male as follows: body length 4.5–5.0 mm; frons wide, frontal triangle glossy black, reaching middle of frons; fronto-orbital plates and upper parafacials glossy black; 3+3 elongated setae on lower katepisternum distinct, but weaker and shorter than in male; f1 without hooks at apex; f2 with only short setulae; t2 without elongated hairs on p surface; mid tarsus not modified.

Remarks. Hydrotaea hsiai Fan, 1965 was described long ago in Chinese (Fan, 1965) and the identity of this species has been unclear. The information given on Hydrotaea hsiai in Xue, Wang & Du (2007) and Xue, Wang & Wang (2007) is fragmentary, contradictory and with errors. However, the combination of two uncommon characters (shining black body, with both thorax and abdomen without pollinosity, and modified tar2–1, with a tuft of setulae in subbasal part) convinces us that the specimens listed above belong to Hydrotaea hsiai . Hydrotaea hsiai is closely related to Hydrotaea tuberculata Rondani, 1866 .

Both species share the following characters: the presence on lower katepisternum of a set of 3 strong and long (about as long as fore coxa length) setae; modified tar2–1 with a tuft of setulae (in basal or apical part respectively); t2 with 2 pd setae and a row of fine p setulae, without ad; t3 with 1–2 av, 1 short ad and 1 pd.

These species differ as follows (males):

- Thorax and abdomen shining (greenish) black, without any pollinosity. In basal half tar2–1 ventrally with a cluster of 4–5 elongated spinulose setulae and 6–7 fine curved hairs (Fig. 1 F). f2 with about 10 strong and long pv setae (1.5– 2x as long as femur width), 5 more sparsely placed setae in basal half and a cluster of 5 more approximated setae in apical half, medially with a bare gap between the two clusters of setae. t2 without elongated setulae on a -surface.................... hsiai Fan

- Scutum matt black, abdomen with thin but distinct grey dusting and a black median vitta. In apical half tar2–1 ventrally with a cluster of 4–5 elongated spinulose setulae, without curved hairs (Fig. 1 E). f2 on pv -surface with a sparse row of 6–8 rather fine setae. t2 on a -surface in apical 2/3 with a row of elongated setulae............................... tuberculata Rondani

The female of Hydrotaea hsiai may also be reliably distinguished by the following set of characters: thorax and abdomen shining (greenish) black, without any pollinosity; fronto-orbital plate and upper paracial shining black; lower katepisternum with a set of 3 approximated medium strong setae, otherwise bare; t2 with 2 pd; t3 with 2 av, 1 short ad and 1 pd.