Rheotanytarsus ashei Yao & Liu, 2022

Liu, Wen-Bin, Yao, Yuan, Chang, Tong, Yan, Chun-Cai & Lin, Xiao-Long, 2022, Contribution to the knowledge of Rheotanytarsus pellucidus species group from China (Diptera, Chironomidae): three new and one newly recorded species, Zootaxa 5188 (2), pp. 145-156 : 146-148

Rheotanytarsus ashei Yao & Liu sp. n.

( Figs. 1A , 2A–E )

Type material. Holotype: male ( NKU: XJ59 ), China, Zhejiang, Xianju, Danzhuxiang , 24. v. 2016, light trap, leg: X. Qi . Paratypes: one male ( NKU: CBL116 ) China, Guangdong, Shaoshan, Shixing, Chebaling National Nature Reserve , 1–11. xii. 2020, malaise trap, leg: L. R. Lu. One male ( NKU: XJ184 ) China, Zhejiang, Taizhou, Xianju, Kuocangshan, Canglingkeng, 10–24. v. 2017, malaise trap, leg: X. Qi. One male ( NKU: ZJ210 ) China, Zhejiang, Yueqing, Lingdi, Hushangyang, 7. iv. 2019, light trap. leg: X.L. Lin .

Etymology. Named after Prof. Patrick Ashe, for his outstanding contribution to the knowledge of Chironomidae ; noun in nominative case.

Diagnosis. The specie can be distinguished from known species of Rheotanytarsus by the following combination of characters: antenna with 13 flagellomeres, and AR 0.26–0.33; thorax with dark brown parallelogram-shaped spots and postnotum dark brown; anal tergite bands separated and horizontal; superior volsella rectangular and broad; inferior volsella slightly curved and apically swollen; gonostylus with pointed apex.

Description. Adult males (n = 4, unless stated).

Total length 1.41–2.08, 1.75 (3) mm. Wing length 1.01–1.42, 1.19 (3) mm. Total length/wing length 1.40–1.47 (3). Wing length/length of profemur 2.05–2.24, 2.16.

Colouration ( Fig. 1A ). Thorax pale brown with dark brown parallelogram-shaped spots and postnotum dark brown, legs pale brown with apical portion of femur darker, and abdomen pale yellow.

Head. Antenna with 13 flagellomeres, ultimate flagellomere 116–172, 138 (3) μm long. AR 0.26–0.33, 0.29 (3). Temporal setae 6–8, 7. Clypeus with 14–20, 17 setae. Tentorium 72–78, 75 μm long, 7–14, 11 μm wide. Palpomere lengths of three specimens (in μm): 24–36, 28; 25–35, 28; 57–63, 60; 77–90, 84; 131–165, 145; Pm5/ Pm3 2.21–2.30, 2.42. Third palpomere with 2 sensilla clavata distally.

Thorax. Dorsocentrals 7–8, 8; acrostichals 6–9, 8; prealars 1. Scutellum with 2–4, 4 setae. Halteres with 7–9, 8 (3) setae.

Wing ( Fig. 2A ). VR 1.61–1.71, 1.66. Brachiolum with one seta, Sc bare, R with 14–17, 16 setae, R 1 with 18–27, 22 setae, R 4+5 with 39–56, 46 setae, M 1+2 with 37–46, 41 setae, M 3+4 with 20–30, 25 setae, false vein with 59–70, 63 setae, Cu with 12–16, 14 setae, Cu 1 with 15–20, 17 setae, PCu with 34–45, 40 setae, An with 19–24, 22 setae, remaining veins bare. Cell r 4+5 with c. 200 setae, m with 3–4, 4 setae, m 1+2 with c. 200 setae, m 3+4 with c. 100 setae, cu+an with c. 130 setae.

Legs. Fore leg bearing single tibial spur, 21–23, 22 μm long. Combs of mid tibia 22–24, 23 μm wide with 15– 26, 22 μm long spur, and 23–36, 29 μm wide with 18–28, 23 μm long spur; combs of hind tibia 20–33, 26 μm wide with 15–30, 21 μm long spur, 29–34, 32 μm wide with 24–27, 25 μm long spur. Tarsomere 1 of mid leg of paratypes with 2–3, 3 (3) sensilla chaetica. Lengths (in μm) and proportions of legs as in Table 1 .

Hypopygium ( Figs. 2 B-E). Tergite IX 86–88, 87 μm long, with 3–7, 5 median setae at base of anal point; anal tergal bands separated and horizontal. Anal point 22–29, 25 μm long, constricted in the middle and apically swollen, bearing 5–7, 6 lateral setae on each side; crests somewhat parallel and nearly reaching apex of anal point, basally developed. Transverse sternapodeme 34–41, 38 μm long, with oral projections. Phallapodeme 42–67, 55 μm long. Gonocoxite 78–94, 84 μm long. Gonostylus 61–80, 70 μm long, gradually tapered and pointed apically. Superior volsella ( Fig. 2D ) 35–43, 38 μm long, broad and somewhat obovoid, with 2–3, 3 anteromedian setae and three dorsal setae near apex. Digitus triangular, outer margin curved from middle, bearing one seta located on cylindrical tubercle near base. Median volsella ( Fig. 2E ) 100–114, 108 μm long, well reaching beyond the apex of inferior volsella, with about six long and thin foliate setae; stem covered with simple setae and slightly curved. Inferior volsella 51–52, 51 μm long, slightly curved and apically swollen, with microtrichia. HR 1.13–1.30, 1.20. HV 2.31–2.61, 2.48.

Female and immatures. Unknown.

Remarks. The new species resembles Rheotanytarsus buculicaudus Kyerematen, 2000 by having similar shapes of anal tergite bands, anal crest and median volsella, but can be separated from the latter species by the following combination characters: superior volsella somewhat obovoid, anal point constricted in the middle, inferior volsella with microtrichia, and gonostylus with pointed apex; whereas superior volsella rounded, anal point with parallel-sided apex, inferior volsella without microtrichia, and gonostylus with blunt apex in R. buculicaudus .

Figures

FIGURE 1. Adult males of Rheotanytarsus pellucidus species group. A. Rheotanytarsus ashei Yao & Liu sp. n., lateral view; B. Rheotanytarsus pinderi Yao & Liu sp. n. lateral view; C). Rheotanytarsus oss, dorsal view; D. Rheotanytarsus vallenduuki Yao & Liu sp. n., lateral view. Scar bars = 500 μm.

FIGURE 2. Rheotanytarsus ashei Yao & Liu sp. n. A. wing; B. hypopygium, dorsal view; C. hypopygium, ventral view; D. superior volsella; E. median volsella.