Hydrobaenus distinctus Makarchenko et Makarchenko, comb. n.

Hydrobaenus distinctus (Makarchenko et Makarchenko), comb. n.

(Figs. 1 –29)

Bryophaenocladius distinctus Makarchenko et Makarchenko, 2006a: 7.

Material. Far East of Russia. Khabarovsk Territory: 5 males, Michurinsk Lake near Khabarovsk City, 5.V. 2009, leg. N. Yavorskaya. Primorye Territory: 2 males, Gribnaya River near Chernigovka Village, 25.IV. 2011, leg. T. Tiunova; 1 mature pupa reared from larva, 1 larva, unnamed stream, Mountain-Taiga Station of the Far Eastern Branch Russian Academy of Sciences, Gornotaezhnoe Village, Ussuryisky Region, N 43°41' 675", E 132°09' 293", 6.V. 2012, leg. E. Makarchenko; 1 male, reared from pupa, 1 pupal exuviae, 1 pupa reared from larva, 1 male, 1 mature pupa, 5 larvae, same data as previous except 6.V. 2013, E. Makarchenko & T. Tiunova; 1 male, same data as previous except 16.V. 2013, leg. E. Makarchenko; 3 males, same data as previous except 27.V. 2013, leg. E. Makarchenko & M. Makarchenko.

Description. Adult male (n = 4). Total length 2.2–2.6 mm. Wing length 1.68–1.96 mm. Total length/wing length 1.30–1.52. Coloration brown, wings grey.

Head. Eyes with short dorsomedian prolongations. Temporal setae including (from one side) 3 inner verticals, 1 outer vertical and 2–5 postorbitals. Clypeus with 5–7 setae. AR 0.97–1.07. Lengths (µm) of palpomeres 1–5: 32, 52–56, 96, 84, 116–128.

Thorax. Antepronotal lobes with V-shaped notch (Fig. 5) and with 2–3 lateral setae. Acrostichals 12–17, beginning close to antepronotum (1 specimen) or some distance from antepronotum (3 specimens) (Fig. 4), dorsocentrals 8–12, prealars 3–4. Scutellum with 6–9 setae.

Wing. R with 11–15 setae, R1 with 3–5 setae, R4+5 with 2–5 setae subapically. Costa extension 56–68 µm. Anal lobe rounded. Squama with 3–5 setae (Fig. 7).

Legs. Spur of front tibia 48 µm. Spurs of mid tibia about 20 µm long, of hind tibia 48–52 µm and 16–20 µm long. Hind tibial comb with 9–11 setae. Pseudospurs on ta1 on all legs absent. Length and proportions of leg segments as in Table 1.

FIGURES 19–29. Hydrobaenus distinctus (Makarchenko et Makarchenko), pupa (19–21) and fourth instar larva (22–29). 19, tergite VII; 20, distal part of anal lobe with macrosetae; 21, tergite VIII and anal segment of male; 22–23, mentum; 24, premandible; 25, mandible; 26, antenna; 27, labral setae; 28, S I of labrum; 29, procercus. Scale bars: Figs. 19, 21– 200 µm; Fig. 20—50 µm; Figs. 22–29—40 µm.

Hypopygium (Figs. 1–3, 6, 8–9). Tergite IX with 16–21 setae along posterior margin and on base of anal point. Anal point without microtrichia, parallel-sided and narrow, 28–40 µm long. Laterosternite IX with 6–9 setae. Transverse sternapodeme 112–136 µm long; oral projections rod-shaped or rounded triangular (Fig. 8). Gonocoxite 192–212 µm long, with double inferior volsellae as in Figs. 1–3. Gonostylus 88–96 µm long, with acutely triangular crista dorsalis (Fig. 9); megaseta 16 µm long.

Pupa (n = 2). Total length 2.8–3.5 mm. Coloration brownish. Exuviae transparent. Abdomen with brown or dark brown apophyses.

Cephalothorax. Frontal apotome with 72 µm long setae. With two median and two lateral antepronotal setae, all thin and hair-like. Precorneal setae lengths (in µm): Pc1—88, Pc2—120, Pc3—80. Distance between Pc1 and Pc2 6–8 µm; distance between Pc2 and Pc 3 6–12 µm. Thoracic horn 260–300 µm long, 20–28 µm wide, with strongly pointed apex, covered by teeth in apical 2/3, spines absent or rarely present in basal 1/3 (Figs. 10–11). Dorsocentrals thin and hair-like; Dc1 48–56 µm long, Dc2 56 µm long, Dc 3 20–28 µm long, Dc4 32–56 µm long; distance between Dc1 and Dc2 32–40 µm; between Dc2 and Dc3 44–84 µm; between Dc3 and Dc 4 12–36 µm.

Abdomen. Tergite I without shagreen. Tergite II without shagreen or with few spinules in anterior half and with fine shagreen in posterior half; posteriomedian shagreen with group of simple spinules in 3–4 rows which larger than other spinules and with apex pointed orally (Figs. 12–14). Tergites III–IV with more intensive shagreen, posterior part with more wide group of spinules pointed orally (Figs. 15–16). Tergites V–VI with shagreen as on previous two tergites but posterior rows of spinules pointed caudally (Figs. 17–18). Tergites VII–VIII with posterior transverse band of 3–4 rows of spinules, sometimes tergite VII with some small spinules medially (Figs. 19, 21). Tergite IX without shagreen. Segment I with 1–2 pairs of lateral setae. Segment II with 3–4 pairs of lateral setae. Segments III–VI with 4 pairs of lateral seta. Lateral setae of segments I–VI hair-like, 40–80 µm long. Segments VII–VIII with 4 pairs of long, strong but not taeniate lateral setae, 92–100 µm long on tergite VII and about 120 µm long on tergite VIII; some lateral setae on tergite VIII might be bifid (Figs. 19, 21). Anal lobe 252– 300 µm long, without fringe. Male genital sac overreaching anal lobe. Anal macrosetae 180–224 µm long, situated little outer of anal lobe apex (Fig. 20), with folded apical part.

Fourth instar larva (n = 6). Coloration yellowish-brown. Total length 4.7–5.0 mm.

Head. Head capsule 320 µm long and 260 µm wide; light yellow, postoccipital margin dark yellow. Labral setae S I palmate, with 12–14 unequal sized branches; S II long and large, S III–S IV short and hair-like (Figs. 27–28); pecten epipharingis consisting of 3 elongated scales with rounded apex. Premandible distally with 2 teeth (Figs. 24). Antenna with 5 segments. Length of antennal segments (in µm): 52, 20, 6, 8, 6. AR 1.3–1.4. Lauterborn organs well developed at apex of second segment and ending at apex of third segment; antennal blade ending near mid to apex of fifth segment (Fig. 26). Mandible dark brown, apical tooth subequal of combined width of inner teeth; seta interna with 7 plumose branches, seta subdentalis with beak-shaped apex (Fig. 25). Mentum with 2 median and 5 lateral pairs of teeth; median teeth with V-shaped notch, slightly lighter than all lateral teeth, 3–6 times wider and slightly higher than first lateral tooth. Ventromental plates extend beyond the last lateral tooth (Figs. 22–23).

Abdomen. Procercus sclerotized posteriorly, 20–28 µm long, 16–28 µm wide, with 7 anal setae 220–240 µm long and 2 thin lateral setae 28–56 µm long (Fig. 29). Supraanal setae 100–120 µm long. Posterior parapods 100– 180 µm long, 80–84 µm wide, in basal ventral part with pair of hair-like setae. Anal tubules shorter than posterior parapods.

Remark. H. distinctus is good separated from all known species of the genus by features adduced in key above.

Distribution and biology. Species is known only from the south part of the Russian Far East, namely from the Amur River basin and Primorye Territory. Pupae and larvae were collected in detritus with old grass of an unnamed stream near Mountain-Taiga Station of the FEB RAS in the southern part of Primorye Territory. The water temperature was 9.7–11.6°C, Ph 6.6–6.9 and the depth 5–15 cm at the time of collection in 2013.