(Figs. 8–11)
Diamesa amplexivirilia Hansen in Hansen & Cook, 1976: 53; Makarchenko 1980: 86, 1981:108, 1985: 77, 2006: 261, 473, 614; Ashe & O’Connor 2009: 270; Krasheninnikov et al. 2020: 591.
Material examined. RUSSIA: 15 adult males, Magadan Region, Tenkinsky District, neighborhood of Sibit-Tyellakh Village, spurs of the peak Vlastny, Olen’ Stream (Kolyma River basin), alt. 1300–1400 m a.s.l., 27–30.VII.1977, leg. Е. Makarchenko; 10 adult males, Chukotka, Wrangel Island, upper stream of Somnitelnaya River, 22.VII.1978, leg. E. Makarchenko; 33 adult males, the same data, except Krasnyi Flag River, middle stream, 4.VII.1979, leg. E. Makarchenko and M. Makarchenko; 138 adult males, 19 pupae and 65 larvae, the same data, except unnamed stream in upper part of Somnitelnaya River, 14.VII–2.VIII.1979, leg. E. Makarchenko and M. Makarchenko; 1 adult male, Severnaya Zemlya Archipelago, Bolshevik Island, Mikoyan Bay, Chernaya River, 1.IX.2019, 79.20768 N, 102.31090 E, leg. A. Krasheninnikov.
Description
Adult male (n = 16). Total length 2.4–4.2 mm. Total length/wing length 0.92–1.23.
Coloration. Dark brown to black; wing grayish, veins yellowish brown.
Head. Eyes hairy, microtrichia visible along lateral eye margin when head is viewed from front. Temporal setae including 3 frontals and 8 verticals. Clypeus with 2–5 setae. Antenna with 8 flagellomeres and reduced plume of setae, 24–48 μm long; number of setae in flagellomeres 1–7, respectively 2–3: 2: 1–2: 1–2: 2: 2: 4; terminal flagellomere with 3 subapical setae, 12–16 μm long and with 3 setae basally, 32–36 μm long; pedicel with 3 setae. Flagellomeres 1–8 length (μm): 38–76–109, 36–55, 28–50, 24–42, 24–38, 24–38, 24–46, 96–134; AR 0.30–0.46. Palpomeres lengths (in μm): 32–40; 40–80; 72–109; 60–109; 78–143. Palpomere 3 in distal part with sensilla capitata with diameter 16 μm. Antennal length/palpal length 1.18–1.45.
Thorax. Antepronotum with 3–15 ventrolateral setae. Dorsocentrals 9–12, prealars 4–10, scutellars 7–22.
Wing. Length 2.24–3.79 mm, width 0.96–1.25 mm. R and R 1 with 6–26 setae; R 4+5 with 5–9 setae in distal part. Costa extension49μm long.RM/MCu2.0–4.6.Anal lobe well developed,rounded.Squama with13–27setae.VR0.93.
Legs. Spur of front tibia 31–46 μm long; spurs of mid tibia 20–46 μm long; of hind tibia 44–80 μm and 30–46 μm long. Hind tibial comb with 9–21 setae. Lengths and proportions of leg segments as in Table 3. We did not include in this table the data on the male from the Severnaya Zemlya Archipelago which are given in the article by Krasheninnikov et al. (2020).
Hypopygium (Figs. 8–11). Laterosternites very extend beyond posterior margin of tergite IX, evenly sclerotized and with relatively dense 5–9 setae, 16–20 μm long. Posterior margin of tergite IX gently rounded, with 4–5 setae (from one side), 8–12 μm long. Tergite bands weak, widely U-shaped (semi-circular) (Figs. 8–9). Anal point visible in dorsal view, relatively well developed and blunt-tipped, angled downwards, without microtrichia (Fig.10), 52–143 μm long; ratio of anal point length to gonostylus length 0.36–0.64. Transverse sternapodeme 68 μm high, triangular, with rounded apex (Figs. 8–9). Gonocoxite 360–400 µm long; superior volsella rounded, fairly well developed, slightly produced disto-medially, with numerous microtrichia. Gonostylus very strongly curved, broadest in basal 0.4–0.5, then abruptly narrowing, with 3 apical teeth of approximately the same size, with strong 3-4 setae between them and megaseta which in form of wide terminal spine (Fig. 11), 8–12 μm long; HR 1.60-2.27.
Pupa and larva are described by Makarchenko (1981).
Remarks. According to their main features, specimens from North America and Eurasia are close together, only slightly different is the male from Severnaya Zemlya, with total length 2.4 mm, wing length 2.24 mm, length of the anal point 52 μm, while males from North America, Wrangel Island and Kolyma River basin are 2.8–4.2 mm long, with wing length 2.52–3.79, anal point length 84–143 μm. We noted earlier that this species is closely related to D. alpina Tokunaga and D. davisi Edwards (Makarchenko 1980) as well as to D. saetheri Willassen and D. serratosioi Willassen (Makarchenko 1985). The barcoding data (see below) confirm a close similarity of D. amplexivirilia with the last two species.
Distribution. Holarctic arcto-alpine species. Known from Canada: Alberta, British Columbia, Northwest Territories, U.S.A.: Montana, Washington, Alaska (Hansen & Cook 1976; Namayandeh 2022) and Russia: Severnaya Zemlya Archipelago (Krasheninnikov et al. 2020), upper streams of Kolyma River, Vrangel Island.