Hydrobaenus majus Makarchenko et Makarchenko, sp. nov.

Hydrobaenus majus Makarchenko et Makarchenko, sp. nov.

(Figs. 5 –18).

Material. Holotype: adult male, Russian Far East, Primorye Territory, Ussuryisky District, Mountain-Taiga Station of the Far Eastern Branch Russian Academy of Sciences, Gornotaezhnoe Village, unnamed stream, N 43°41.675', E 132°09.293', 6.V. 2013, leg. E. Makarchenko & M. Makarchenko. 19 Paratypes: 5 adult males, 2 pupae with larval skins, 3 larvae, the same data as holotype, except 16.V. 2013, leg. E. Makarchenko; 1 adult male, the same data as holotype, except 27.V. 2013, leg. E. Makarchenko; 1 pupa, 4 larvae, the same data as holotype, except 10.V. 2014, leg. E. Makarchenko & M. Makarchenko; 3 adult males, Khabarovsk Territory, Bolshekhehtsyrsky Nature Reserve, Golovina Stream, Ussuri River basin, N 48°11.131', E 134°41.039', 13.V. 2015, leg. N. Yavorskaya.

Etymology. The species name is derived from the Latin word majus, which means May. All the examined material was collected in May.

Adult male (n=4). Total length 2.5–3.3 mm. Wing length 2.0– 2.28 mm. Total length/wing length 1.25–1.45.

Colouration. Thorax, abdomen and legs brown to dark brown. Wing greyish.

Head. Eyes pubescence, with short dorsomedian prolongations Temporal setae 9–10, including 5–6 verticals and 4 postorbitals. Clypeus with 8–10 setae. Antenna with 13 flagellomeres and well developed plume; apex of 13th flagellomere pointed. AR 1.52–1.80. Length of 5 palpomeres (in µm): 20–32, 60–68, 116–120, 100–120, 136–160.

Thorax. Antepronotum with 3 lateral setae. Acrostichals 8–16, dorsocentrals 7–16, prealars 4–7, scutellum with 6– 12 setae in one row.

Wing. R with 6–10 setae, R1 and R4+5 without setae. R4+5 ending distal of apex M3+4 and costa extension. Costa extension 48 µm. Anal lobe well developed, rounded. Squama with 11–16 setae.

Legs. Spur of fore tibia 56–60 µm long. Spurs of mid tibia 24–24 µm and 20 µm long. Spurs of hind tibia 56–60 µm and 20 µm long. Hind tibial comb with 10–11 setae. Front leg without pseudospurs on ta1; mid leg with 0–1 pseudospur, hind leg with 2 apical pseudospurs on ta1 and; sometimes hind legs with 1 apical spur on ta1. Hind leg on ta 1 in basal part with 6–10 sensilla chaetica. Lengths and proportions of legs as in Table 1.

continued.

Hypopygium (Figs. 5–8). Tergite IX roundish, with 13–28 setae. Anal point 16–36 µm long, with rounded apex. Laterosternite IX with 8–11 setae on each side. Transverse sternapodeme 128 µm long, with rod-like oral projections (Fig. 8). Virga 40–60 µm long, consists of 3–5 setae. Gonocoxite 216–268 µm long; inferior volsella like in Fig. 5. Gonostylus 88–116 µm long, with preapical crista dorsalis (Fig. 5); megaseta 12–16 µm long. One male has 2 megasetae. HV 2.41–3.37; HR 2.08–2.20.

Pupa (n=3). Total length 4.0– 4.3 mm. Colouration brownish, abdominal tergites light yellow to brown. Exuviae transparent. Tergites II–VIII and sternites II–VIII with brown or dark brown apophyses.

Cephalothorax. Frontal apotome almost smooth, with 2 tubercles and 2 setae 144 µm long. Antepronotum with two median and two lateral antepronotal setae. One median antepronotal seta thin and hair-like, another seta strong, ca 4 µm wide and sometimes branched near apex (one female). Both lateral antepronotals thin and hair-like. Thoracic horn 368– 400 µm long (males) or 384 µm long (female), with strongly pointed apex and with extension in distal third, covered by teeth (Figs. 9–10). Precorneal setae lengths (in µm): Pc1—72–100, Pc2—136–140, Pc 3—20–36. Dorsocentrals thin and hair-like; Dc1, 3, 4 56–50 µm long (males) and 48–68 µm long (females), Dc2 40 µm long. Distance between Dc1 and Dc2 44–52 µm; between Dc2 and Dc3 36–62 µm; between Dc3 and Dc4 32–36 µm.

FIGURES 9–18. Hydrobaenus majus sp. nov., pupa (9–12) and larva of fourth instar (13–18). 9–10, thoracic horn of male (9) and female (10); 11, tergite VI; 12, tergite VIII and anal segment; 13, S I and labral lamella; 14, premandible; 15, 17, mentum; 16, distal part of mandible; 18, antenna; Scale bars: Figs. 9–10—50 µm; Figs. 11–12—200 µm; Figs. 13–16, 18—20 µm.

Abdomen. Tergite I without shagreen. Tergite II with shagreen of spinules which in middle part small, at anterior edge spinules larger; at posterior edge shagreen with relatively large spines situated in 3 rows and their apex pointed orally. Shagreenation of tergites III–IV is same as tergite II, but the spinules at posterior edge of the same size as in the middle part. Tergites V–VI with shagreen of spinules as tergites III–IV but at posterior edge without spinules pointed orally (Fig. 11). Tergites VII–IX with weak shagreen of spinules in the middle part. Sternites without shagreen but sometimes some spinules situated on sternites I–V. Segment II with weak PSB. Sternites IV–VII with PSA. Segment I with 0–1 pairs of lateral setae. Segments II–V with 3 pairs of hair-like lateral setae. Segment VI with 1–2 pairs of short hair-like lateral seta and 2 pairs long taeniate lateral setae (Fig. 11). Segments VII–VIII with 4 pairs of long taeniate lateral setae (Fig. 12). Anal lobe 320–380 µm long, with fringe of 28–30 setae which 68–100 µm long, occupy two-thirds of the anal lobe and extend to anal macrosetae, often these setae 12–64 µm long situated between anal macrosetae (Fig. 12). Male genital sac overreaching anal lobe 24 µm. Anal macrosetae 272–304 µm long.

Fourth instar larva (n = 4). Colouration of head brown, body segments yellowish or yellowish-brown. Total length 4.7–6.0 mm.

Head. Brownish. Labral setae S I plumose (Fig. 13), S II strong, S III weak and hair-like, S IV short; labral lamella abutting sockets of S I roundish-triangular (Fig. 13). Pecten epipharingis consisting of 3 equal scales. Premandible brown, distally with 2 teeth (Fig. 14). Antenna 112–128 µm long, with 6 segments. Length of antennal segments (in µm): 76–80, 13–20, 8–12, 8–10, 4–5, 1.5–1.7. AR 1.58–2.22. Apex of segment 2 with stylus 7.5–8.4 µm long and lauterborn organs which ending at apex of 3rd segment; antennal blade ending near mid or apex of 5th segment; one large and small ring organs in proximal 1/3 of basal segment and sometimes one ring organ in distal half of basal segment (Fig. 18). Mandible dark brown, with yellowish apical tooth, which shorter of combined width of inner teeth; seta interna with 6 plumose branches, seta subdentalis long, with beak-shaped apex (Fig. 16). Mentum with 2 yellow or yellowish median teeth and 6 pairs of dark brown lateral teeth; median teeth lower than the second laterals; first lateral teeth length equal or slightly lower of median teeth and slightly narrower of median teeth. Ventromental plates extend beyond last lateral tooth (Figs. 15, 17). Maxilla with pecten galearis.

Abdomen. Procercus 28–52 µm long, 28–36 µm wide, with 7 anal setae 430–496 µm long and 2 thin lateral setae. Supraanal setae 160–224 µm long. Anal tubules shorter than posterior parapods. Posterior parapods with simple hooks in apex.

Diagnostic characters and taxonomic notes. The new species is closely related to Far Eastern species H. sikhotealinensis and H. maiorovi Makarchenko et Makarchenko but adult males of these species are not readily separable from the H. majus by morphological features. Male of H. maiorovi has narrower tergite IX and more massive rounded oral projections of transverse sternapodeme than other two species, subapical part of gonostylus with microtrichia (Khamenkova et al. 2014, Fig.2), as well as the lack of pseudospurs on ta1 and ta2 of middle and hind legs. Males of H. sikhotealinensis and H. majus are closely related because of bare subapical part of gonostylus and rod-like projections of transverse sternapodeme, ta1 and ta2 of middle and hind legs with pseudospurs (Makarchenko & Makarchenko 2006; Makarchenko et al. 2009). These two species differ with each other only by shape the posterolateral edge of tergite IX, that is angular in the male of H. sikhotealinensis (Figs. 1–4) and rounded in H. majus (Figs. 5–7). Data for all other features are overlapped. In such cases, a great help in the identification of species can provide a comparative study of the morphology of the pupae and larvae, as well as DNA barcoding. Preimaginal stages for H. maiorovi are unknown but pupae and larvae of H. sikhotealinensis and H. majus are well separated by many features.

H. sikhotealinensis has a pupa with thoracic horn which tapers towards the top (Makarchenko & Makarchenko 2009, Fig. 48), length 310–320 µm. Abdominal segment VI with 3 pairs of simple lateral setae, segment VIII with 5 pairs of taeniate lateral setae (Makarchenko & Makarchenko 2009, Fig. 49). Mentum of larva with one light-brown or brown median tooth and six pairs of lateral teeth the same colour.

H. majus has a pupa with thoracic horn with extension in distal third (Figs. 9–10), length 368–400 µm. Abdominal segment VI with 1–2 pairs of short hair-like and 2 pairs long taeniate lateral setae, segment VIII with 4 pairs of taeniate lateral setae (Fig. 12). Mentum of larva with 2 yellow or yellowish median teeth and 6 pairs of dark brown lateral teeth (Figs. 15, 17).

Results of DNA barcoding of H. majus and H. sikhotealinensis are given below.