(Figs. 30–33)
Hydrobaenus jacuticus Makarchenko et Makarchenko, 2011: 392, Figs. 3–4.
Hydrobaenus kotsuki Makarchenko et Makarchenko, 2012: 121, Figs. 33 –47; syn. n.
Material. Far East of Russia. Sakha (Yakutia) Republic: 1 male, Neryungrinsky District, Gorbyllakh River, 1.VIII. 2010, leg. E. Makarchenko; 1 male, same data as previous except Chulman River, 2.VIII. 2010, leg. T. Tiunova. Amurskyi Region: 1 male, extracted from mature pupa, 2 mature pupae, 1 pupa with larval skin, 4 larvae, Selemdzhinskyi District, Northern part of Zlatoustovsk Village, Kazachenskyi Stream (Zeya River basin), 25.VII. 2008, leg. D. Kotsuk. Magadanskyi Region: 1 male, extracted from mature pupa, 2 mature pupa, 1 mature larva, Tenkinskyi District, environs of Sibit-Tyellakh Village, Olen’ Stream (Kolyma River basin), 24.VII. 1977, leg. E. Makarchenko.
Remarks. This species was described by a single adult male from South Yakutia (Makarchenko & Makarchenko 2011). Later, from the Amur Region has been described a new species H. kotsuki Makarchenko et Makarchenko, 2012 by adult male, extracted from the mature pupae, as well as by pupa and larva. After comparing of this species with additional material from the Kolyma River basin, it became clear that the new species was described incorrectly and H. kotsuki should be synonymized with H. jacuticus. Below we present diagnosis of the male adult of this species by all materials from the Russian Far East.
Diagnosis. Adult male (n = 4). Total length 2.3–2.5 mm. Eyes with short dorsomedian prolongations, pubescent. Temporal setae including (from one side) 3–4 inner verticals, 1–2 outer verticals and 2–5 postorbitals. Clypeus with 4–6 setae. AR 0.93–1.22. Antepronotal lobes with 2–3 lateral setae. Acrostichals 5–6 (situated in middle of scutum), dorsocentrals 4–5, prealars 2–3. Scutellum with 6 setae. Wing length 1.7–1.8 mm. Costa extension 12 µm. Anal lobe well developed. Squama with 6–8 setae. LR 1 0.64–0.72.
Hypopygium (Figs. 30–33). Tergite IX with 10–14 setae and nacked anal point, tapering to the top, 16–22 µm long. Transverse sternapodeme 80 µm long; oral projections roundish or roundish triangular. Dorsal part of inferior volsella with nacked and finger-shaped projection; ventral part roundish and covered by microtrichia and some setae. Gonostylus slightly curved, without crista dorsalis; megaseta 12 µm long. Virga consists of 2–4 black spines.
Distribution. Known from Amur and Kolyma River basins and south part of Sakha (Yakutia).