Rhithrogena sibirica Brodsky 1930

Rhithrogena sibirica Brodsky 1930

(Figs. 60–77)

Material examined. RUSSIA. Yakutiya: Lena River Basin, Dabai River, near Dabai Village, 2.VIII 1987, V Bogatov, 1 male imago; Aldan River Basin, Chulman River, upper Nerjungri City, 25.VII 2006, T Tiunova, 4 larvae; Magadanskaya Oblast’: Tauj River, middle part, 11.VII 2001, S Kocharina, 1 male imago; Tauj River Basin, Kava River, 9.VII. 2001, S Kocharina, 1 male imago; same place, 19.VII 2001, 1 male imago; same place, 30.VII 2001, 3 male imagines; Tauj River Basin, Chelomdzha River, 14.VII 2001, S Kocharina, 3 male imagines. Chitinskaya Oblast’: Selenga River Basin, Kaban’ya River, about 45 km upper mouth, 26.IV 2009, N Bazova, 1 larvae. Amurskaya Oblast’: Bureya River, near Novo-Burejsk Village, 25.VI 2004, T Tiunova, 1 male imago; Zeya River, near Krasnoyarovo village, 13.VI 2004, T Tiunova, 3 male imagines; same place, 24.VI 2004, 9 male imagines; Zeya River, near Zeya City, 20.VI 2004, T Tiunova, 30 male, 2 female imagines; Zeya Hydro-Electric Power Station Basin, Giljuj River, middle part, 19.VI 2004, T Tiunova, 9 male imagines; Zeya Hydro-Electric Power Station Basin, small stream 2 km below mountain Zolotaya Gora, 20.VI 2004, T Tiunova, 1 male imago. Khabarovskiy Kray: Amgun River Basin, Suluk River, about 10 km below Suluk Village, 16.VI 1994, T Tiunova, 9 larvae; Amgun River, near Dopsikan mountain, 24.VI 1994, T Tiunova, 23 male, 4 female imagines, 18 male, 6 female subimago, 5 larvae; Amgun River, near Postishevo Village, 28.VI 2004, T Tiunova, 4 male, 1 female imago, 1 male, 1 female subimago, 3 larvae; Ussuri River Basin, Chuken River, mouth, tributary of Chor River, 10.VI 1995, T Tiunova, 7 larvae; Sukpaj River, near Sukpaj Village, tributary of Chor River, 22.VI 1998, T Tiunova, 8 male imagines; Chor River, near Srednehorsky Village, 13.VI 1995, 4 male imagines; Chor River, 1.5 km below Gvasjugi Village, 14.VI 1995, T Tiunova, 30 male imagines; Chor River, near Kafe Village, 15.VI 1995, T Tiunova, 2 male, 2 female imagines (reared from larvae); Amur River, near Tsimmermanovka Village, 21.VI 2000, T Tiunova, 27 male, 3 female imagines; Mutii River, tributary Yaj River, below motor-car bridge, line Khabarovsk – De-Kastri, 30.VI 2005, T Tiunova, 5 male imagines; Bureya River Basin, Chegdomyn River, near Chegdomyn Village, 13.VII 2003, T Tiunova, 3 male imagines, 7 larvae; Nimakan River, mouth, 15.VII 2003, T Tiunova, 1 male imago; Niman River, 1.5 km upper mouth Nimakan River, 15.VII 2003, T Tiunova, 4 male imagines; Priokhot’e, Khetana River, 7 km upper mouth, tributary of Ul’ya River, 16.VIII 1985, V Zherikhin, 1 male imago; Kuhtuj River, about 10 km upper mouth, 10–12.VIII 1998, T Tiunova, 7 larvae; same place, 28–30.VI 1999, T Tiunova, 2 male, 3 female imagines, 5 larvae; Okhota River, about 6 km upper mouth, 1–5.VIII 1998, T Tiunova, 13 larvae; same place, 25–27.VI 1999, T Tiunova, 5 larvae; Okhota River, about 30 km upper mouth, 6–8.VIII 1998, T Tiunova, 4 male, 5 female imagines (reared from larvae); Lantar River, 2.5 km upper mouth, 28.VII 1999, T Tiunova, 1 male, 3 female imagines, 1 male, 1 female subimago; Uda River, about 5 km upper mouth, 13.VIII 2000, T Tiunova, 3 male imagines; Uda River, about 140 km upper mouth, 15– 20.VIII 2000, T Tiunova, 5 male imagines; Tatar strait Basin, Tumnin River, near mouth Tun’ River, 18– 19.VII 1997, T Tiunova, 2 male imagines; Tumnin River, near Gapanki mountain, 29–30.VI 1997, T Tiunova, 3 male, 2 female imagines; Aldan River Basin, Maya River, 1 km below Nel’kan village, 5–8.VIII 1999, T Tiunova, 1 male imago (reared from larvae), 6 male imagines. Primorskiy Kray: Armu River, upper part, tributary Bolshaya Ussurka River, 15.VI 1990, T Tiunova, 1 male imago; Bolshaya Ussurka River, 1,5 km upper mouth Daljnaya River, 23.VI 1990, T Tiunova, 1 male imago; Tuschnaya River, mouth, tributary Bikin River, 19.VI 1998, T Tiunova, 1 male imago.

Description. Male imago (in alcohol). Dimensions: length (mm): body 8.1–12.0; forewings 9.0–12.0; cerci 16.0–27.0. Thorax: pronotum brown, mesonotum dark brown; scutellum dark brown with a white cross-sectional strip; sublateroscutum white (Fig. 60); metanotum and metasternum dark brown. Length (mm) of foreleg segments: femora 1.7–2.5; tibia 1.9–2.6; tarsal segments 0.2–0.3, 0.9–1.5, 0.9–1.4, 0.6–1.1, 0.4– 0.6. Wings hyaline, veins from dark brown to brown. Abdomen: terga 2–7 dark brown with the lateral area darker, translucent; terga 2 with a pair of large whitish spots at the distal margin; terga 3–8 with a pair of light spots at the distal margin and a pair of small specks in the middle area; terga 8–9 opaque. Sterna translucent, dark brown with a lighter base and small white specks that are poorly expressed. Forceps dark brown; middle area of styliger plate light brown (Fig. 61). Penis lobes brownish, inner margin darker, strongly supported edge of the styliger plate; penis lobes long with widely placed top portions, with a middle portion expanded and with a long (Figs. 62–63), sharp shoot at the base (Fig. 63–64); titillators absent. Cerci: proximal third brown, distal portion from light brown to yellow.

Female imago. Dimensions: length (mm): 7.0–9.7; forewings 9.0–11.3; cerci 8.8–12.0. Thorax: pronotum brown with a light spot in the distal area; mesonotum brown; medioscutum and submedioscutum light brown; anteronotal protuberance dark brown, scutellum dark brown with a white top portion, lateroparapsidal suture light brown, lighter than the submedioscutum. Abdomen: terga and sterna colored as in males; sternum 7 dark brown; sterna 2–5 with a pair of oblique, light colored strokes in the distal area and a pair of small, light specks in the middle area. Cerci: brown at the base and yellowish at the tip.

Male subimago. Thorax: pronotum and mesonotum white; medioscutum and submedioscutum light brown; anteronotal protuberance and lateroparapsidal suture dark brown; scutellum, parascutellum and posterior scutal protuberance light brown. Forelegs brown, middle and hind legs yellow, tinged with brownish color; femora of all legs with a dark longitudinal spot in the middle area. Wings light brown, translucent.

Abdomen: terga 1–9 dark brown, opaque; terga 2–6 with a pair of light oval specks near the distal margin and a pair of small light round spots in the middle area; terga 7–8 with a pair of small light specks. Sterna 1–6 brown, 7–9 dark brown; sterna 2–7 with a pair of oblique light colored strokes in the distal area and a pair of light colored, round specks in the middle area. Cerci brown, uniformly colored.

Mature larva. Dimensions: length (mm): body 8.0–10.2, cerci 6.5–8.2. Head: forehead brown (Fig. 65). Maxilla with 8 comb-shaped setae at the apical margin (Fig. 68); labrum width approximately 4.4 times longer than the length (Fig. 66). Thorax: pronotum brown with lighter anterior and posterior margins; mesonotum brown; at the base of the wing pads, there are two small curved strips. Legs brown; femurs of all legs may or may not have a dark, indistinct spot in the middle of the light central area; setae on the dorsal surface of forefemora of the identical form, extended with a rounded apex (Fig. 73). Claws of fore- and middle legs with 2 subapical denticles (Figs. 75–76). Length (mm) of leg segments are as follows. Foreleg: femur 1.3–1.9, tibia 1.4–1.7, tarsus 0.6–0.7; middle leg: femur 1.4–2.1, tibia 1.3–1.6, tarsus 0.4–0.5; hind leg: femur 1.7–2.6, tibia 1.1–1.9, tarsus 0.4–0.5. Abdomen: terga brown, usually uniformly; terga 3–6 with a pair of small dark stripes in the middle area; central portion of the posterior margin of terga 5 having long and pointed teeth of uniform size (Fig. 77). Sterna brown; posteromedian emargination on sterna 9 poorly expressed (Fig. 74). Gills white, often with the inner half of the tergalius being dark pink or grayish-brown; gill I large, with an even outer margin (Fig. 69); gills III–IV with a rounded ledge on the posterior margin (Figs. 70–71); gill VII broadened in the middle area (Fig. 72). Cerci yellowish or whitish.

Distribution and biology. Rhithrogena sibirica is an East Palaearctic species that is distributed in East Siberia (Kluge 1980), including southern Yakutiya (Tiunova et al. 2009), Magadanskaya Oblast’(Zasypkina 1980; Arefina et al. 2003), Kamchatka (Levanidova 1972), Altai (Brodsky 1930; Beketov 2005), the south of Russian Far East (Tshernova et al. 1986; Kluge 1997; Tiunova 2007a, 2008, 2009, Tiunova & Potikha 2005) and Mongolia (Bajkova & Varychanova 1978; Braasch 1979, 1986; Landa & Soldán 1983; Soldán et al. 2009).

Larvae of this species were found in stones, gravel and pebbles in rivers of different types.