Boreoheptagyia sasai Makarchenko et Endo 2008, sp. n.

Boreoheptagyia sasai Makarchenko et Endo, sp. n.

(Figs 26–33)

Boreoheptagyia brevitarsis (Tokunaga) sensu Makarchenko (1981: 89, 1985: 38, 2006: 259).

Type material. Holotype male, RUSSIA: North-Eastern Russia, Ten’kinsky County, Magadan Region, Kolyma River Basin, Vlastnyi Peak not far from Sibit-Tyellah Village, Olen’ Stream, 1.100–1.300 m a.s.l., 11–27.vii.1977, E. Makarchenko & S. Kocharina (IBSS FEBRAS). Paratypes: 11 males, 4 females as holotype. 2 males, JAPAN: Hokkaido, Shintoku, Yutomuraushi River, 700 m a.s.l., Malaise trap, 11–21.vi.1999, K. Endo; 1 male, same as previous except 21.vi–2.vii.1999, Malaise trap, K. Endo; 1 male, 1 female, Hokkaido, Obihiro, Opirineppu River, 620 m a.s.l., 5–15.vi.2000, Malaise trap, K. Endo; 2 males, same as previous except 13.ix–1.x.1999, K. Endo; 1 male, same as previous except 5–15.vi.2000, Malaise trap, K. Endo.

Etymology. Named in honor and memory of the famous Japanese chironomidologist and colleague Prof. Manabu Sasa.

Diagnostic characters. The male is well separated from other species of the genus by the presence of setae on mesanepisternum II and preepisternum, and by the field of small spinules distal of transverse sternapodeme (Figs 30, 32).

Male (n = 9)

Total length 2.4–2.7 mm. Wing length 1.61–2.13 mm. Total length / wing length 1.17–1.29.

Coloration. Head, thorax and legs brown to dark brown, abdomen grayish to yellowish.

Head. Temporal setae includes 6–7 postorbitals, 30–31 outer verticals, and 26–31 inner verticals. Clypeus with 11–12 setae. Antenna with 13 flagellomeres, antennal plume reduced, pedicel with 4 setae. Lengths (in µm) of flagellomeres 2–13: 17–29, 25–34, 31–42, 35–46, 39–42, 34–46, 36–46, 38–55, 38–42, 38–46, 34–42, 88–101. Number of setae on flagellomeres 2–13 as: 4–5, 6, 8, 9–10, 8–9, 9–10, 8, 8–9, 8, 8, 7–8, 4. Subapical seta of terminal flagellomere 11–15 µm long. AR 0.11–0.20. Lengths (in µm) of palpomeres 1–5: 27–30, 63– 80, 101–109, 92–118, 160–193. Antennal length / palp length 1.35–1.40. Head width / palp length 1.04–1.16.

Thorax. Antepronotum with 6–11 lateral setae. Acrostichals 33–36; dorsocentrals 24–26 in anterior and posterior groups; prealars 19–26 in 2 rows; supraalars 2; preepisternals 6–13; median anepisternum II with 4– 6 setae. Scutellum with 58–62 setae. Longest and shortest acrostichals 36–42 µm and 11–21 µm long.

Wing 0.52–0.62 mm wide. Costal extension 64–80 µm long. Anal lobe well developed, fully fringed. Alula without setae. Squama with 32–48 setae. R with 14 setae, R 1 with 13–17 setae, R 4+5 with 3–7 setae, R 2+3 usually reduced, often only basal part visible. RM/MCu 1.80–2.25.

Legs. Spur of foretibia 34–42 µm long; spurs of midtibia 34–42 µm and 34–38 µm long, of hind tibia 34– 55 µm and 34–38 µm long. Hind tibial comb with 10–12 setae. Mid ta 1 with 4–7 pseudospurs, ta 2 with 1 pseudospur, 23–27 µm long; hind ta 1 with 10–12 pseudospurs, ta 2 with 1 pseudospur, 23–27 µm long. Lengths and proportions of legs of specimens from Kolyma River Basin and from Hokkaido as in Tables 5 and 6, respectively.

Hypopygium (Figs 28–33). Tergite IX with 20–27 setae. Laterosternite IX with 12–17 setae. Transverse sternapodeme 46–60 µm wide. Aedeagal lobe long, narrow; phallapodeme narrow, well visible. With field of small spinules distal of transverse sternapodeme. Gonocoxite 201–205 µm long; basal lobe rounded, with 1–3 short setae. Gonostylus 95–103 µm long, with wide median part and short narrow apical part, ending in short megaseta. HR 2.20–2.73.

Remarks. The males from Kolyma River Basin and from Hokkaido differ in the lengths and proportions of the leg segments (see Tables 5 & 6), while in other characters both populations are very similar or identical.

Distribution. The species is known from localities in the Kolyma River Basin in Northeastern Russia and from Hokkaido, Japan.