Cladotanytarsus bilyji Giłka et Puchalski, 2017

Puchalski, Mateusz & Giłka, Wojciech, 2017, Cladotanytarsus Kieffer (Diptera: Chironomidae): several distinctive species reviewed on the basis of records from Canada and USA, Zootaxa 4242 (2), pp. 344-358 : 347-350

Cladotanytarsus bilyji Giłka et Puchalski , sp. nov.

( Figs 2 , 3 )

Type material. Holotype, adult male: CANADA, MANITOBA, Lake Winnipeg, Old Fishing Dock (51°33’ N / 96°43’ W), 16 June 1971, leg. E. Johnson & M. Roberts (prep. O.A. Saether) . Paratype: USA. OHIO. Clermont County, Shayler Run at Baldwin Road (39°07’06” N / 84°12’59” W), 20 September 1999, 1 adult male, leg. J. Trybula. Ex coll. M. & J.E. Sublette . Deposit in DEUM.

Derivatio nominis. The specific epithet honours Bohdan Bilyj (Etobicoke, Canada), to commemorate his contribution to the study of Nearctic Cladotanytarsus .

Diagnosis. Anal point strongly elongate, evenly tapering toward apex. Superior volsella slender, narrowed at mid length, with field of microtrichia on basal part dorsally. Stem of median volsella ca. 40 µm long, longer than its setiform and 7–8 furcate lamellae, all arranged evenly on median and apical part of stem. Inferior volsella with lateral knee-like extension at base, with well-developed angular dorsomedian ridge.

Description. Adult male (n = 2).

Colouration (slide-mounted specimens). Eyes black. Antennal pedicel, tentorium, scutal stripes, scutellum, postnotum and sternum dark brown. Head capsule, antennal flagellum, mouthparts and abdomen greenish to light brown; hypopygium and legs slightly darker. Wing membrane transparent with greenish undertone, veins brownish.

Head. Eyes reniform, broadly separated. Antenna with 13 flagellomeres, AR 0.92–0.94; plume fullydeveloped. Frontal tubercles cylindrical, 12–24 µm long. Lengths of palpomeres 2–5 (in µm): 32–36, 84–104, 100– 108, 164 (n = 1). Clypeus semicircular, with 14–15 setae.

Thorax chaetotaxy. Ac 7–8, Dc 8, Pa 1, Scts 4–6.

Wing ( Fig. 2 ). Length 1520–1720 µm. Shape, venation pattern and chaetotaxy typical of the genus, as shown in Fig. 2 ; Cu1, R1 and m3+4 bare or with few macrotrichia at most; VR Cu 1.18–1.28.

Legs. Fore leg tibia with straight spur ca. 20 µm long. Combs of mid and hind leg tibiae separated, each bearing straight spur: ca. 15–20 µm long on mid leg and up to ca. 30 µm long on hind leg. Basitarsus of mid leg with 2–4 hook-shaped sensilla chaetica. For lengths of leg segments and leg ratios, see Table 2 .

Hypopygium ( Fig. 3 ). Gonostylus shorter than gonocoxite, ca. 70 µm long, with blunt apex. Anal tergite with V-type separated bands and 7–8 median setae placed in two rows. Anal point elongate, evenly tapering towards slender apex (slightly deformed in paratype specimen, Fig. 3 C), bearing 7–8 spinulae between well-developed crests, entire area surrounding base of anal point covered with microtrichia ( Fig. 3 A, C). Superior volsella slender, elongate, more or less narrowed at mid length, bearing field of microtrichia dorsally only on basal part or proximal 1/3 at most, 6–11 dorsal setae, 1–2 setae on anteromedian margin and 3 long setae placed on conical tubercles at base. Digitus curved, long, extending far beyond superior volsella, with finger-like tip ( Fig. 3 A, D). Stem of median volsella slightly curved and directed posteriorly, long (ca. 40 µm), bearing several setiform and 7–8 furcate lamellae: 4 strong and 3–4 weaker, all arranged evenly on median and apical part of stem ( Fig. 3 B, E). Inferior volsella with lateral knee-like extension at base, evenly curved and directed posteromedially, darkly pigmented dorsomedian ridge distinctly protruding, angular ( Fig. 3 A, B, F).

Remarks. Apart from the strongly elongate anal tergite point, this new species can be distinguished from other Cladotanytarsus on the following combination of characters: the superior volsella slender and narrowed at mid length, with field of microtrichia only on basal part dorsally, the median volsella composed of a long stem and 7–8 furcate lamellae and the inferior volsella with a lateral knee-like extension at the base, bearing a well-developed angular dorsomedian ridge.

According to preliminary determinations (Sublette, Saether; pers. comm.), there are at least 8 or 9 additional Cladotanytarsus species recorded from the Lake Winnipeg region (locus typicus of C. bilyji ), which should be compared with those described by Bilyj and Davies (1989) from northwestern Ontario. We examined all the Cladotanytarsus species by Bilyj (op. cit.) known from adult males (excl. C. aeiparthenus Bilyj, 1989 ). However, even when atypical variations are included, most of the males examined (except for C. muricatus Bilyj, 1989 , see remarks below) do not fully fit the present concept of the strongly elongate and narrow hypopygial anal point. Males of those species have relatively short anal points ( C. daviesi Bilyj, 1989 , C. pinnaticornis Bilyj, 1989 ), without a distinct distal elongation and/or at least distinctly broadened at the base. Males of C. elaensis Bilyj, 1989 have acute anal points, but are relatively broad and surrounded with a microtrichia-free area at the base; in C. tribelus Bilyj, 1989 the anal point is narrow and parallel-sided but moderately long ( Bilyj & Davies 1989; figs 6, 8). As far as the general shape of the anal point is concerned, there is a slight resemblance between the males of C. fusiformis Bilyj, 1989 and those of C. bilyji ; although these two species can be easily separated also by the shape of the superior volsella, which in the former is nearly half as long as the digitus, and the median volsella has a smaller number of lamellae (cf. Fig. 3 and Bilyj & Davies 1989, fig. 4). Originally, C. fusiformis was also compared with C. nigrovittatus ( Goetghebuer, 1922) . The latter species is presumed to be the closest relative of C. bilyji (see the key below). Finally, the males of C. mancus (Walker, 1856) [or the C. mancus group sensu Giłka (2001)], often misidentified with C. nigrovittatus , should also be included in this comparison. They differ in the length proportions of the median volsella stem-lamellae (the stem longer relative to its lamellae in C. bilyji ), the number of lamellae (greater in C. bilyji ), and the arrangement of median setae on the anal tergite (dispersed in C. mancus ).

Figures

FIGURE 2. Cladotanytarsus bilyji Giłka et Puchalski, sp. nov., male. Wing.

FIGURE 3. Cladotanytarsus bilyji Giłka et Puchalski, sp. nov., male. A, B — hypopygium in dorsal (A) and ventral aspect (B) (holotype); C — anal point (variation, paratype); D — superior volsella and digitus (variation); E — median volsella (holotype); F — inferior volsella (paratype) (D—magnified ca. 2 times relative to A; E, F—magnified ca. 3 times relative to A).

Tables

TABLE 2. Leg segment lengths (µm) and leg ratios of male Cladotanytarsus bilyji sp. nov. (n = 1 when segments missing or deformed).

	fe	Ti	ta1	ta2	ta3	ta4	ta5	LR
p1	627–715	369	731	398	399	221	111	1.98
p2	649–900	472–642	288–295	162–192	118–140	66–73	52–70	0.46–0.61
p3	704–826	915–964	450	288	244	155	103	0.65