Diamesa alpina Tokunaga 1936

Diamesa alpina Tokunaga

(Figs. 1–7)

Diamesa alpina Tokunaga, 1936: 539; Makarchenko 1980: 82–86, 1985: 81–82, 2006: 261; Willassen 1986: 124–125; Makarchenko & Yamamoto 1995: fig. 2; Kobayashi & Endo 2008: 56; Ashe & O’Connor 2009: 269.

Diamesa kurobedistalis Sasa et Okazawa, 1992:59.

Diamesa kurobenagaia Sasa et Okazawa, 1992: 61.

Material examined. CANADA: 1 adult male, Jasper-Banff Area, Rocky Mountains, 13. VI.1957, leg. L. Brundin; U.S.A.: 3 adult males, Alaska, Hebert River, about 0.5 mi. downstream of glacier, 20.II.2010, leg. J. Hudson; RUSSIA: 1 adult male, Kamchatka, Avacha River, 11. VI.1970, leg. V. Levanidov; 1 adult male, the same data, except, Korf Bay, unnamed stream near Tilichiki Village, 8. VIII.1972, leg. E. Nikolaeva; 5 adult males, the same data, except, Pravaya Kamchatka River, 7–8. VII.1996, leg. E. Makarchenko; 2 adult males, Chukotka Autonomous Okrug, Anadyrskyi District, unnamed stream of Velikaya River basin, 1. VIII.1980, leg. E. Makarchenko; 3 adult males, Kurile Islands, Kunashir Island, Sernovodsk Village, Tiurino River, 24.IV.1978, leg. E. Makarchenko; 3 adult males, the same data, except Onekotan Island, Rezvyi Stream, 7. VIII.1996, leg. V. Teslenko; 1 adult male, the same data, except Shiashkatan Island, 12. VIII.1996, leg. V. Teslenko; 3 adult males, Magadan Region, Olskyi District, 137 km of Kolymskaya Road, Ola River, 13. V.2017, 60.412194 N, 151.514564 E, leg. Е. Khamenkova; 2 adult males, the same data, except, mouth of Ola River, 03. V.2019, 59.580514 N, 151.272686 E, leg. Е. Khamenkova; 3 adult males, Khabarovsk Territory, Solnechnyi District, Gornyi Village, Silinka River, 22. VII.1985, leg. E. Makarchenko.

Description

Adult male (n = 10, except when otherwise stated). Total length 2.6–3.3 mm. Total length/wing length 0.95– 1.15.

Coloration. Dark brown to black. Wing greyish, with brownish veins.

Head. Eyes hairy, reniform. Temporal setae including 2–3 frontals and 8–10 verticals. Clypeus with 2–4 setae. Antenna with 8 flagellomeres and reduced plume of setae (Fig. 4); terminal flagellomere with 1–2 subapical setae, 16–28 μm long. Length of 1–8 flagellomeres (μm): 104–120, 34–50, 32–42, 27–38, 29–34, 24–36, 34–48, 104–140; AR 0.33–0.42. Palpomere length (μm): 36–40, 56–72, 88–92, 80–92, 100–136. Palpomere 3 in distal part with sensilla capitata with diameter 16–20 μm. Head width/palpal length 1.27–1.39. Antennal length/palpal length 1.0–1.37.

Thorax. Antepronotum with 8–13 ventrolateral setae. Dorsocentrals 7–11, prealars 2–5, scutellars 24–26.

Wing. Length 2.60–3.60 mm, width 0.76–0.98 mm. Costal extension absent. Anal lobe rounded, sometimes slightly reduced. Squama with 9–21 setae. R and R 1 with 6–20 setae, R 4+5 with 6–15 setae. RM/MCu 2.4–2.8.

Legs. Spur of front tibia 26–42 µm long. Spurs of mid tibia 38–40 µm and 36–48 µm long. Spurs of hind tibia 50–76 µm and 29–42 µm long. Hind tibial comb with 15–24 setae. Length (μm) and proportions of leg segments for males from Kurile Island, Amur River basin, Chukotka, Kamchatka and North America are as in Table 1. Most long legs and different proportions of leg segments have specimens from Magadan Region and for them the data are given in Table 2.

Hypopygium (Figs. 1–3, 5–7). Laterosternites not protruding beyond the posterior margin of tergite IX in East Palaearctic specimens (Figs. 2–3) or slightly (60–68 µm) extending beyond posterior margin of tergite IX in Nearctic adult males (Figs. 6–7). Posterior margin of tergite IX partly straight to slightly rounded, with some weak setae along, 9–10 µm long. Laterosternites with 9–12 weak setae, 9–15 µm long. Tergite bands broad and distinctly U-shaped (Figs. 2–3, 6–7). Anal point often visible in dorsal view, angled downwards (Fig. 1), 25.2–50.4 µm long; ratio of anal point length to gonostylus length 0.15–0.24. Transverse sternapodeme (TSA) triangular, usually with a spire-shaped apex (Figs. 5–6), 72–160 µm high, 180–224 µm wide at the base; TSA height/TSA width 0.40–0.80. Gonocoxite 360–400 µm long; superior volsella rounded, with microtrichia and sometimes short setae (Fig. 5). Gonostylus 192–208 µm long, weakly curved, gradually narrowing towards distal end, with 3–4 apical teeth of approximately the same size, with strong setae between them and megaseta which in form of wide terminal spine (Figs. 2–3, 6–7), 8–12 μm long; HR 1.75–2.20.

Pupa was described by Tokunaga (1936).

Larva unknown.

Remarks. As noted above, the revision revealed that males from the Eastern Palaearctic are characterized by hypopygium with laterosternites that do not extend beyond the posterior margin of tergite IX, while in males from North America (Alaska and Alberta), the laterosternites extend beyond the posterior margin of tergite IX. Therefore, it is necessary to change the diagnosis of the species given by Willassen (1986) in which he indicated that the laterosternites extend beyond the posterior margin of tergite IX. This error is due to the fact that Willassen analyzed the material only from Alaska and ignored the figure of a male hypopygium from Kamchatka (Makarchenko 1980, Fig. 3A), in which laterosternites do not extend beyond the posterior margin of tergite IX. It is possible that different species inhabit the Eastern Palaearctic and Nearctic, but to confirm this a comparison with the support of DNA barcoding is recommended.Also noteworthy are adult males from the Magadan Region (Ola River basin) possessing the longest legs and leg’s indexes differing from other populations, namely LR 1 0.58, BV 1 4.60–4.79, SV 1 3.53–3.64 in specimens from Magadan Region and LR 1 0.62–0.67, BV 1 3.98–4.38, SV 1 3.04–3.27 in specimens from other regions.

Distribution. Known from Japan, Kurile Islands, Kamchatka, Magadan Region, U.S.A. (Alaska) and Canada (Alberta).