(Figs. 39–56)
Material. Holotype: adult male, Russian Far East, Magadan Region, Ten’kinskyi District, Olen’ Stream (upper stream of Kolyma River), about 3 km from Sibit-Tyellakh Village, 25.VI. 1977, leg. E. Makarchenko. Paratypes: 1 adult male and 2 males extracted from mature pupae, 1 pupa and 2 pupal exuviae, 1 larva and 3 larval skins taken from pupae, same data as holotype; 1 pupa with larval skin, 4 larvae, East Siberia, Republic of Buryatia, Severobaikalskyi (North Baikal) District, Davsha River (Baikal Lake basin), 5.VII. 2000, leg. L. Kravtsova.
Adult male (n= 2)
Total length 3.4–3.6 mm. Wing length 2.28–2.52 mm. Total length/wing length 1.43–1.49. Colouration brown, wing grey.
Head. Temporal setae 9–11, including outer verticals and postorbitals, inner verticals absent. Clypeus massive, with 13–14 setae. Antenna with 13 flagellomeres and well developed plume; AR 1.02–1.13. Palp with 5 palpomeres. Palpomere length (in µm): 28 –32, 52–56, 80–92, 68–72, 92– 104.
Thorax. Brown. Antepronotum with 3–7 lateral setae. Acrostichals 1–4, only in lightly coloured oval area; dorsocentrals 8–11 (in 1 row); prealars 3–4; scutellars 16.
Wing. R with 4–6 setae, R 1 with 2 setae, R 4 + 5 with 2–3 setae subapically. Apex of R 4 + 5 distal of apex M 3 + 4. Cu 1 straight. Costa extension absent. Anal lobe rectangular-rounded. Squama with 18–20 setae.
Legs. Spur of fore tibia 56–60 µm. Spurs of mid tibia 40–48 µm long, of hind tibia 64–68 µm and 42–44 µm long. Hind tibial comb with 11 setae. Length and proportions of leg segments as in Table 3.
Hypopygium (Fig. 39). Tergite IX with 19–26 long setae; anal point narrow, subparallel-sided, slightly widened apically and bare. Laterosternite IX with 3–7 setae on each side. Transverse sternapodeme without oral projections. Gonocoxite 224–244 µm long; inferior volsella as in Fig. 39. Gonostylus 100–104 µm long, widest in basal two-thirds, strongly narrowing towards tip, apical part slightly curved inwards, covered with few long setae in outer part, without crista dorsalis, megaseta absent.
Pupa (n= 3). Total length 4.5–4.6mm.
Cephalothorax. Frontal setae simple, 244–260 µm long, arising from cephalic tubercles on frontal apotome, 32–40 µm long. Frontal apotome and cephalic tubercles covered with small tubercle-like spines. Thoracic horn brown 320–336 µm long, tapering to pointed apex and covered with spinules (Fig. 40). Nearest of thoracic horn 3 branched precorneals: Pc 1 with 6–14 branches, Pc 2 with 9–14 branches, Pc 3 with 5–6 branches. Median two antepronotals with 2–4 branches and 9–10 branches. Lateral antepronotal setae not observed (replaced with pore). Three dorsocentrals in group and Dc 4 slightly distant; Dc 1 with 5–9 branches, Dc 2 with 2–5 branches, Dc 3 with 4–8 branches, Dc 4 with 3–4 branches.
Abdomen. Shagreenation of tergites as in A. levanidovi but spines along posterior edge of tergites III–V located in smaller brown spots at base. PSA present on sternites IV–VII. Segment I without lateral setae. Segments II–VI with 3 pairs of lateral setae and one pore, segment VII with 2 pairs of lateral setae. Segment VIII with 0–1 pair of lateral setae. Anal lobe 288–304 µm long and 400–416 µm wide, with light brown chitinized projection 60–100 µm long, with 2–3 spinules in apex and with 0–5 weakly developed spinules in lateral part (Figs. 41 –44, 56). Male genital sac extending beyond anal lobe and apex of anal lobe projection (Figs. 45, 56).
FIGURES 46–55. Abiskomyia rivalis sp. nov., larva of fourth instar. 46, seta submenti; 47, antenna; 48, distal part of antenna; 49, S I and labral lamella; 50, distal part of premandible; 51 –52, 54– 55, mentum; 53, distal part of mandible. Figs. 46, 51– 55 — 50 µm; Figs. 48–50 — 20 µm.
Fourth instar larva (n = 2). Total length 4.5 mm.
Head. Head capsule dark-brown, postoccipital margin black. S I of labrum large, oval and finely plumose on edge, S II simple and strong, S III small and hair-like, S IV short and spinous. Labral lamella dark brown, triangular (Figs. 49, 62). Premandible with two well separated subequal apical teeth, and with two inner teeth shorter than apical teeth (Fig. 50); brush developed and consisted of simple long spines. Antenna with 5 segments, located on pedestal with pointed projection 36–40 µm long; segment 4 and 5 of similar size; two ring organs in basal part of segment 1, distal ring organ with long seta; one lauterborn organ on apex of second segment and one on apex of third segment; blade ending at middle part of segment 4; style 8 µm long, placed on subapical part of segment 3 (Figs. 47–48); AR 1.86–2.14. Mandible brown, with 4 teeth, apical tooth shorter than combined width of 3 inner teeth; seta long, tapering to pointed apex (Fig. 53); seta interna with 4 plumose branches. Pecten galearis developed but sometimes not visible. Median tooth of mentum with a flat top (probably slightly ground off), with the first pair of lateral teeth slightly lighter than other four pairs of lateral teeth; first pair of lateral teeth smallest and located at base of middle part of median tooth; ventromental plate broad, subtriangular; covered with small spines (Figs. 51 –52, 54–55, 59– 61); setae submenti plumose, split into 4–5 branches, sometimes branched at apex (Fig. 46).
Anal tubules short and roundish at apex. Procercus dark, sclerotized, nearly as long as wide, bearing 7–8 apical anal setae of different length: 1 seta 464–560 µm long, 2 setae 320–368 µm long, 3 setae 224–240 µm long and 1–2 setae 112–120 µm long. Body with simple and branched setae.
Diagnosis. See the keys.
Etymology. The species is named from Latin rivalis – living in stream.
Ecology. Pupae and larvae were collected from stones in mountain stream covered with moss, with water temperatures 0.4–0.8 °C.