Rheotanytarsus aphelus, Wang, Xinhua & Guo, Yuhong, 2004

Wang, Xinhua & Guo, Yuhong, 2004, A review of the genus Rheotanytarsus Thienemann & Bause from China (Diptera: Chironomidae: Tanytarsini), Zootaxa 650, pp. 1-19 : 2-4

Rheotanytarsus aphelus sp. n. ( Figs. 1–3 )

Type material. Holotype male (BDN No. 07015), China, Tianjin City, Ji County, Yuqiao Reservoir. X. 17. 1987. Leg. X. Wang, sweep net.

Etymology. From Latin apheles, smoothness, simple, referring to the smooth superior volsella.

Diagnosis. The species differs from other members of the acerbus group by having well developed oral projections of the transverse sternapodeme, more numerous acrostichals, and fewer setae anterior to the anal point.

Male imago (n=1)

Total length 3.40 mm. Wing length 1.90 mm. Total length / wing length 1.79. Wing length / profemur length 2.02. Coloration brown, eyes black.

Head. Antenna with 13 flagellomeres. AR 0.97, ultimate flagellomere 528 µm long. Temporal setae consisting of 8 inner, 4 outer verticals and 4 postorbitals. Clypeus with 18 setae. Tentorium 140 µm long, width 30 µm. Palpomere lengths (in µm): 40; 52; 134; 144; 224.

Wing ( Fig. 1 ). VR 1.42, Cu 840 µm long.

Thorax. Acrostichals 26; dorsocentrals 9; prealars 1. Scutellum with 8 setae.

Legs. Spur of front tibia 30 µm. Spurs of middle tibia 40 and 32 µm long, of hind tibia 48 and 44 µm long. Combs of middle leg composed of 18 and 14 free teeth, hind leg of 18 and 16 free teeth. Lengths and proportion of legs (Table 1):

Hypopygium ( Figs. 2–3 ). Anal tergite bands V type, widely separated medially, extending almost to base of anal point. Tergite IX with 8 setae. Anal point tapering gradually to rounded point. Crests well developed, subparallel. Phallapodeme 70 µm long. Transverse sternapodeme 60 µm long, straight, with pointed oral projections. Gonocoxite 140 µm long. Superior volsella 46µm long, rectangular on left side, oval on right, with 2 inner and 7–8 dorsal setae, 1 long seta on ventral surface near middle. Digitus absent. Inferior volsella 89 µm long. Median volsella ( Fig. 3 ) 66µm long, lamellae on about 35–40 µm long stem. Gonostylus abruptly narrowed in apical 1/2, recurved, 140 µm long. HR 1.00; HV 2.43.

Distribution. The species is known from Yuqiao Reservoir, a typical mesotrophic water body in Tianjin (Palaearctic China).

Figures

FIGURES 1 – 5. Figs. 1 – 3. Rheotanytarsus aphelus sp. n. Holotype, male imago: 1. Wing, 2. Hypopygium, 3. Median volsella. Figs. 4 – 5. Rheotanytarsus bullus sp. n. Holotype, male imago: 4. Wing, 5. Hypopygium