Polypedilum (Tripodura) falcatum, Zhang, Ruilei, Song, Chao, Wang, Liqing & Wang, Xinhua, 2015

Zhang, Ruilei, Song, Chao, Wang, Liqing & Wang, Xinhua, 2015, Two new species of the acifer species group of Polypedilum subgenus Tripodura Townes from China (Diptera: Chironomidae), Zootaxa 3918 (4), pp. 571-578 : 572-573

Polypedilum (Tripodura) falcatum sp. n.

( Figs 1A–H )

Type material. Holotype: male (BDN. 12654), CHINA: Sichuan Province, Garzê County, Yajiang, 2830m, 14. VI. 1996, light trap, X. Wang. Paratypes: 19 males. 9 males: Sichuan Province, Baoxing County, Xilong Town, 1100m, 19. VI. 1996, light trap, X. Wang. 1 male: Sichuan Province, Daocheng County, Sang dui, 3730m, 10. VI. 1996, X. Wang. 4 males: Sichuan Province, Daocheng County, Daocheng River, 3700m, 11. VI. 1996, X. Wang. 1 male: Sichuan Province, Litang District, Shiliang River under Zhaisang Bridge, 3520m, sweep net, 13. VI. 1996, X. Wang. 2 males: Sichuan Province, Yajiang County, Xinduqiao, 3150m, sweep net, 9. VI. 1996, Y, Du. 2 males: Ningxia Autonomous Region, Liupan Mountain Natural Conversation, 6. VIII. 1987, sweep net, X. Wang.

Etymology. The species name is from Latin “ falcatus ”, means sickle-shaped, referring to the shape of the superior volsella of P. (T.) falcatum sp. n.

Diagnostic characters. The new species can be distinguished from other allied species by the following combination of characters: presence of 2 areas of faint markings on wing; superior volsella sickle-shaped with 0–2 outer setae; a tuft of short setae present or absent dorsally on apical inner margin of superior volsella; inferior volsella straight, uniformly tapering towards apex, bilobed apically.

Description. Male imago (n = 9). Total length 2.03–2.90, 2.52 mm. Wing length 1.35–1.88, 1.63 mm. Total length/ wing length 1.81–2.15, 1.98. Wing length / length of profemur 2.11–2.85, 2.58.

Coloration. Head brown. Thorax brown with darker vittae, postnotum, preepisternum, scutellum; halteres yellowish brown. Coloration of legs variable: all legs entirely yellow; or all femora brown with darker apices, fore tibiae and tarsi brown, tibiae and tarsi of mid and hind legs yellow. Abdominal segments yellow to yellowish brown.

Head. AR 0.65–0.80, 0.72. Ultimate flagellomere 310–360, 340 µm long. Temporal setae 10–12, 11, including 2–3, 2 inner verticals, 4–5, 5 outer verticals and 3–5, 4 postorbitals. Clypeus with 12–17, 14 setae. Tentorium 90–110, 102 µm long, 23–35, 28 µm wide. Palp 5-segmented, length (in µm) of palpomeres: 25–35, 31; 30–35, 33; 70–93, 83; 85–108, 102; 140–175, 158; the 3rd segment bearing 2–3 sensilla chaetica.

Wing ( Fig. 1A ). VR 1.33–1.42, 1.38. R with 15–20, 17, R1 with 9–14, 12, R4+5 with 20–28, 24 setae. Squama with 4–5, 4 setae. Wing with two areas of faint markings, one at the middle of the anal cell, one at the base of cell m3+4 and across vein Cu1.

Thorax. Dorsocentrals 9–13, 11; acrostichals 12–17, 14; prealars 3–4, 4. Scutellum with 5–9, 6 setae.

Legs. Terminal scale ( Fig. 1B ) of front tibia 38–50, 44 µm long, triangular and pointed apically. Spur of median tibiae 38–43, 40 um long including 18–23, 21 µm long comb, un-spurred comb 18–23, 20 µm long; spur of posterior tibia 43–50, 47 µm long including 23–30, 26 µm long comb, un-spurred comb 18–28, 23 µm long. Width at apex of front tibia 40–45, 43 µm, of median tibia 40–56, 46 µm, of hind tibia 48–60, 53 µm. Lengths (in m) and proportions of legs as in Table 1 .

Hypopygium ( Fig. 1C –I). Tergite IX subrectangular, with 2–3 setae placed medially on the base of anal point; anal tergite bands short, thickly bent downwards and terminating abruptly well before the median area of the IX th tergum. Laterosternite with 1–2 setae. Anal point broad, 45–65, 57 µm long; the lateral projections weak ( Fig. 1H ), or absent, only with shoulders on tergite IX ( Fig. 1C ); dorsally, with a V-shaped ridge bearing 5–6 short setae on each side. Phallapodeme 63–88, 74 µm long; transverse sternapodeme 25–40, 32 µm long. Superior volsella ( Fig. 1D–G ) sickle-like, with 0–2 outer setae, a tuft of short setae present or absent dorsally on the apex of inner margin. Inferior volsella 75–108, 90 m long, straight, gradually narrowed towards apex, bilobed apically; dorsally with 9–12 curved setae and a long apical seta. Gonocoxite 105–125, 117 µm long. Gonostylus 113–133, 122 µm long, with 3–4 long setae in 1 row along inner margin. HR 0.88–1.03, 0.96. HV 1.76–2.22, 2.06.

Distribution. The species is known from both the Palaearctic and Oriental regions of China.

Remarks. The male adult of the new species resembles those of P. (T.) acifer Townes and P. (T.) sidoniensis Moubayed in having a sickle-like superior volsella, and a broad and apically rounded anal point. Main distinguishing characters between them are given in Table 2 .

A tuft of short setae on apical inner Present or absent Absent Present margin of superior volsella

Inferior volsella Apically bilobed and narrowed Parallel-sided Broad apically Special attention should be paid to the variations in the lateral projection of the anal point, and the superior volsella in the new species. In this study, 20 specimens were examined. Nine specimens have weak lateral projections beside the anal point ( Fig. 1H ), other 11 specimens only with shoulders on tergite IX ( Fig. 1C ). One specimen has no outer seta on both superior volsellae ( Fig. 1D ); one specimen has 1 outer seta on one superior volsella ( Fig. 1G ) and has 2 outer setae on the other superior volsella ( Fig. 1F ); eighteen specimens have one outer seta on both superior volsellae. Eight specimens have a tuft of short setae on the apical inner margin of the superior volsella ( Fig. 1F. G ), the remaining specimens lack thsese setae. Similar variations were observed in P. (Uresipedilum) cultellatum Goetghebuer ( Niitsuma, 1992; Zhang & Wang, 2004.), P. (Polypedilum) iriofegeum Sasa & Suzuki (Sasa & Suzuki, 2001) and P. (Pentapedilum) sordens (van der Wulp) ( Sasa, 1985). Presence or absence of outer setae of the superior volsella is a key character to separate the nubifer and the nubeculosum groups in the subgenus Polypedilum s. str. ( Sasa & Kikuchi, 1995; Saether & Sundal 1999). Position of the outer seta of superior volsella is often used as an important character in phylogenetic analysis ( Vårdal et. al. 2002, Saether et. al. 2010.). Based on foregoing remarks, the different number and positions of the outer seta on the apical projection of the superior volsella may be intraspecific variations.

Figures

FIGURES 1 A – H. Polypedilum (Tripodura) falcatum sp. n. A. Wing. B. Fore tibial scale. C. Posterior margin of tergite IX. D – G. Superior volsella. H. Hypopygium, dorsal and ventral view.

Tables

TABLE 1. Lengths (in Μm) and proportions of legs of P. (T.) falcatum sp. n., male.

PI	PII	PIII
fe 570–700, 629	650–800, 717	700–850, 764
ti 340–450, 382	500–620, 550	580–730, 649
ta1 680–820, 747 ta2 430–500, 464	290–350, 317 160–205, 182	390–520, 451 220–290, 251
ta3 310–350, 331 ta4 240–260, 250 ta5 110–120, 115 LR 1.82–2.06, 1.92	105–130, 116 65–80, 73 50–65, 59 0.56–0.61, 0.58	175–225, 204 100–125, 111 70–85, 75 0.66–0.77, 0.75

TABLE 2. Main distinguishing characters between P. (T.) falcatum sp. n., P. (T.) acifer Townes and P. (T.) sidoniensis Moubayed.

	falcatum sp. n.	acifer	sidoniensis
AR	0.65–0.80	1.02–1.22	0.4
LR	1.82–2.06	1.60–1.71	Unknown
Wing marking	Faint	Absent	Absent
Lateral projections of anal point	Weak or only with shoulders	Weak	With shoulders
Notch at the base of anal point	Absent	Absent	Present
Median setae on tergite IX	2–3	2–3	9
Outer setae of superior volsella	0–2	1	1