Tanytarsus heliomesonyctios Langton 1999

Tanytarsus heliomesonyctios Langton, 1999

Figures 1–4.

Tanytarsus sp. Langton, 1992 (ecology, parthenogenesis, phenology).

Tanytarsus heliomesonyctios Langton, 1999: 212, Fig. 1 b, d, f (female); Fig. 2 b, e, f (pupa).

Tanytarsus heliomesonyctios Langton, 1999; GU 073186 – GU 073192 | Female, pupa, larva, Stur & Ekrem 2011: 32, Figs 27– 32.

Tanytarsus heliomesonyctios Langton, 1999; AAC2863|Male, available from: http://www.boldsystems.org/index.php/Public_ RecordView?processid=CHRFI417-11

Tanytarsus heliomesonyctios Langton, 1999; Makarchenko et al., 2019, Figs 10–13.

Material examined. 4 males, Russia, Magadan region, Monomtai Lake, 27–28.vii.2018, leg. Е. Hamenkova; 4 males, same data, 2.viii.2018, leg. Е. Hamenkova; 4 males, Republic of Sakha (Yakutia), Big Darpir Lake, 4.viii.2018, leg. Е. Hamenkova.

Description. Adult male (n=3). Total length 3.6–4.7 mm; wing length 2.8–3.7 mm. Total length / wing length 1.17–1.61.

Colouration. Ground colour of thorax, scutellum, maxillary palpomeres, haltere, legs and abdomen brown; antenna, scutal stripes and postnotum dark brown.

Head. Frontal tubercles cone-shaped, 10–24 μm long and 7–17 μm wide. Temporal setae 16. Clypeus with 16–20 setae. Antenna with 13 flagellomeres, 1638–1701 μm long; ultimate flagellomere 1050–1071 μm. AR 1.67– 1.79. Maxillary palpomeres 2–4 combined 752–928 μm long, their individual lengths (in μm): 80–96: 216–248: 200–240: 256–344. Antenna length/palp length 1.81–2.18.

Thorax. Acrostichals 4–10, dorsocentrals 8–14, prealars 2. Scutellum with 18 setae.

Wing width 1.0– 1.05 mm. VR 0.94–1.18. R with 23–29, R 1 with 3–23, R 2+3 with 10–30, R 4+5 with 45–65, M 3+4 with 26–50, Cu 1 with 9 setae. VR 0.94–1.18. Brachiolum with 1 seta. Membrane covered with sparse macrotrichia in distal half.

Legs (see Table 1). Spur of fore tibia straight, slightly curved apically 24–31 μm long. Combs of mid and hind tibiae separated; each comb bears straight or slightly curved spur, 27–31 μm (mid tibia) to 31–41 μm long (hind tibia). Basitarsus of mid leg with 2–5 sensilla chaetica.

Hypopygium (Figs 1–4). Anal tergite with 2–3 median setae (rarely without setae) and great microtrichia-free area surrounding of base. Dark tergite bands separated medially, not reaching anal point crests. Lateral teeth and lateral setae absent. Anterior margin of tergite IX with small protrusions. The anal point is triangular shape with a wide base (85–102 μm long) and a narrower apical part (17 μm), armed with 10–12 spinulae placed in row between crests (102–133 μm long and height 7–10 μm in lateral view); microtrichia absent between crests; 16 lateral setae on each side of anal point. Gonocoxite 231–238 μm long, along the inner margin with 3–4 setae. The width of the transverse sternapodeme 119–126 µm. Phallapodeme 187–221 μm long. Superior volsella oval-shaped (65–85 μm long, 41–44 μm wide in dorsal view and 31 μm wide in lateral view), bearing 3–4 strong anteromedian and 6–8 fine dorsal setae, microtrichia absent. Digitus short (14 μm long and 7 μm wide). Stem of median volsella 78–92 μm long, bearing long simple and foliate setae that extend beyond the top of the inferior volsella. Inferior volsella 102–153 μm long, with 21–24 setae. Gonostylus straight 255–262 μm long and expanded in the proximal third (71–85 μm), tapering to widely rounded apex. HR 0.91.

Remarks. Adult males of T. heliomesonyctios keys to the T. lugens species group due to the missing or poorly developed digitus, usually the lack of median tergite setae, a large microtrichia free area around the anal point base, and foliate lamellae with long tips on the median volsella (Ekrem 2003). Currently, the T. lugens species group includes six species, namely, T. bathophilus Kieffer, 1911, T. lugens (Kieffer, 1916), T. konishii Sasa & Kawai, 1985, T. latiforceps Edwards & Thienemann, 1941, T. trux Gilka & Paasivirta, 2007 and T. heliomesonyctios Langton, 1999 (Ekrem 2003, Gilka & Paasivirta 2007). Adult males of T. heliomesonyctios most similar with two species of T. lugens species group— T. bathophilus and T. lugens. Table 2 shows the main morphological features of males. Males of T. heliomesonyctios are distinguished by a large body size, a longer last antenna segment and maxillar palp, thoracic chetotaxy, the presence of medial setae on tergite IX (rarely medial setae are absent), the presence of poorly developed digitus and elongated median volsella (see Table 2).

Distribution. Holarctic species. Previously known from Ellesmere Island in the Canadian high Arctic and the archipelagos Spitsbergen and Jan Mayen (Norway) as well as in Finnmark, northern Norway (males). For the first time noted the fauna of Russia. This is the second record of adult males.