Rheotanytarsus vallenduuki 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 : 153

Rheotanytarsus vallenduuki Yao & Liu sp. n.

( Figs 1D , 5A–E )

Type material. Holotype: male ( NKU: XL794 ), China, Guangdong, Guangzhou, Lanxi , 12. iv. 2018, light trap, leg. X.L. Lin.

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

Diagnosis. The species can be distinguished from known species of Rheotanytarsus by the following combination of characters: antenna with 13 flagellomeres, AR 0.32; thorax with dark brown parallelogram-shaped spots and postnotum dark brown; anal tergite bands fused, arching upwards basally and horizontal in the middle; anal point with slightly swollen apex; digitus reduced and not visible; the stem of median volsella curved and covered with relatively short foliate setae and simple setae; median volsella with long, thin and foliate setae apically; inferior volsella curved and with equal-width; gonostylus gradually tapered and rounded apically.

Description. Adult male (n = 1)

Total length 1.57 mm. Wing length 1.05 mm. Total length/wing length 1.50. Wing length/length of profemur 1.99.

Colouration ( Fig. 1D ). Thorax pale brown with dark brown parallelogram-shaped spots and postnotum dark brown; legs pale brown, femur and tibia of fore leg darker apically, femur of mid and hind legs darker apically; abdomen pale yellow.

Head. Antenna with 13 flagellomeres, ultimate flagellomere 142 μm long. AR 0.32. Temporal setae 8. Clypeus with 18 setae. Tentorium 58 μm long, 11 μm wide. Palpomere lengths (in μm): 49, 40, 104, 146, 238; Pm5/ Pm3 2.29. Third palpomere with 2 sensilla clavata distally.

Thorax. Dorsocentrals 7; acrostichals 10; prealar 1. Scutellum with 4 setae. Halteres with 7 setae.

Wing ( Fig. 5A ). VR 1.59. Brachiolum with one seta, Sc bare, R with 16 setae, R 1 with 20 setae, R 4+5 with 41 setae, M 1+2 with 45 setae, M 3+4 with 30 setae, false vein with 81 setae, Cu with 13 setae, Cu 1 with 14 setae, PCu with 44 setae, An with 23 setae, remaining veins bare. Cell r 4+5 with c. 250 setae, m with 3 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, broken. Combs of mid tibia 25 μm wide with 21 μm long spur, and 32 μm wide with 26 μm long spur; combs of hind tibia 33 μm wide with 24 μm long spur, 35 μm wide with 29 μm long spur. Tarsomeres of mid leg lost during DNA extraction. Lengths (in μm) and proportions of legs as in Table 4 .

Hypopygium ( Figs. 5 B-E). Tergite IX 70 μm long, with two median setae at base of anal point; anal tergal bands fused, arching upwards basally and horizontal in middle. Anal point 8 μm long, relatively short and only reaching a little beyond tergite, with slightly swollen apex, bearing four lateral setae on each side; crests of V-type and fused apically, nearly reaching apex of anal point. Transverse sternapodeme 32 μm long, with obvious oral projections. Phallapodeme 43 μm long. Gonocoxite 73 μm long, basal microtrichia area right triangle. Gonostylus 60 μm long, gradually tapered and rounded apically. Superior volsella ( Fig. 5D ) 35 μm long, rectangular, with two anteromedian setae, four dorsal setae and one ventral seta. Digitus reduced and not visible. Median volsella ( Fig. 5E ) 90 μm long, well reaching beyond apex of inferior volsella, with about five long, thin and foliate setae apically; stem slightly curved, covered with simple setae and about two relative short foliate setae basally. Inferior volsella 59 μm long, markedly curved with equal width, with microtrichia. HR 1.22. HV 2.62.

Female and immatures. Unknown.

Remarks. The new species resembles Rheotanytarsus buculicaudus Kyerematen, 2000 by having similar shapes of anal tergite bands, median volsella and inferior volsella, but can be separated from the latter species by the following combination characters: superior volsella rectangular, inferior volsella with microtrichia, cell m with only three setae, and tibia of fore leg darker apically; whereas superior volsella oval-like, inferior volsella without microtrichia, cell m with 20 setae, and tibia of fore leg pale 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 5. Rheotanytarsus vallenduuki Yao & Liu sp. n. A. wing; B. hypopygium, dorsal view; C. hypopygium, ventral view; D. superior volsella; E. median volsella.

Tables

TABLE 4. Lengths (in μm) and proportions of legs of Rheotanytarsus vallenduuki Yao & Liu sp. n., adult male (n = 1)

	fe	ti	ta 1	ta 2	ta 3	ta 4	ta 5	LR	BV	SV
P 1	525	278	635	294	235	174	91	2.28	1.81	1.26
P 2	555	383	-	-	-	-	-	-	-	-
P 3	600	434	302	171	170	104	62	0.70	2.64	3.42