Rhithrogena bajkovae Sowa 1973

Rhithrogena bajkovae Sowa 1973

(Figs. 24–42)

Rhithrogena bajkovae Sowa, 1973:24 (male imago).

Rhithrogena quadrinotata Sinitshenkova, 1982:63 (male imago, female imago and larva); Kluge, 1995:27 (synonym).

Material examined. RUSSIA. Chukotka: Evenkiya, Taimura River, mouth Neptene River, 17–22.VII 1982, N Sinichenkova, 8 male, 1 female imagines, 1 male subimago; Chitinskaya Oblast’: Amur River basin, Amazar River, 300 m upper Amazar Village, 26–27.VIII 2004, T Tiunova, 38 male imagines, 14 larvae; Shilka River, near mouth Chasovinka River, 24.VII 2005, T Tiunova, 7 male imagines; Nercha River, upper Zmeinka Village, 27.VII 2005, T Tiunova, 11 male imagines; Chernaya River, 500 m upper motor-car bridge, line Khabarovsk - Chita, 29–30.VII 2005, T Tiunova, 21 male imagines, 1 female subimago. Amurskaya Oblast’: Bureya River, turn on Gulikovka Village, 16.VIII 2003, T Tiunova, 24 male imagines; Bureya River, 500 m below Kulikovka Village, 17–18.VIII 2003, T Tiunova, 15 male imagines; same place, 22.VIII 2004, T Tiunova, 12 male imagines; same place, 3.VIII 2005, T Tiunova, 1 male imago; same place, 6.VIII 2006, T Tiunova, 11 male imagines; Amur River, mouth Ganukan River, 2 km below Kasatkino Village, 12.VIII 2003, T Tiunova, 22 male imagines; Amur River, Souznoe Village, 5.VIII 2003, T Tiunova, 17 male imagines; Amur River, Ignashino Village, 28–29.VIII 2004, T Tiunova, 25 male imagines; Zeya River, Krasnoyarovo Village, 22.VIII 2004, T Tiunova, 25 male imagines; Zeya River, upper Zagan Village, 2.VIII 2005, T Tiunova, 9 male imagines; Zeya River, upper Mazanovo Village, 5.VIII 2006, T Tiunova, 9 male imagines; Zeya River, 9 km below mouth Gramatucha River, 19.IX 2007, V Teslenko, 5 male imagines; same place, 19.IX 2008, 2 male imagines; Bolshoi Ol’doi River, 300 m upper motor-car bridge, line Khabarovsk - Chita, 25.VIII 2004, T Tiunova, 1 male imago, 6 larvae; same place, 31.VII 2005, T Tiunova, 5 male imagines, 3 larvae; Sigikta River, near Bolshoi Never Village, 3.VIII 2006, T Tiunova, 6 male, 1 female imagines; Tygda River, mouth, tributary Zeya River, 12.IX 2007, E Makarchenko, 11 male imagines. Jewish Avtonomnaya Oblast’: Kuldur River, 1 km upper mouth Sutara River, 2 km below Dvurech’e Village, 19.VIII 2003, T Tiunova, 17 male, 2 female imagines; Bidzhan River, 300 m upper Preobrazhenovka Village, 15–16.VIII 2004, T Tiunova, 1 male imago; Stolbukha River, 5 km upper Stolbovoe Village, 18.VIII 2004, T Tiunova, 1 male imago; Amur River, Pompeevka River, mouth, 19–20.VIII 2004, T Tiunova, 2 male imagines. Khabarovskiy Kray: Gur River, tributary Amur River, 100 m upper motor-car bridge, line Khabarovsk – Komsomolsk, 1.VIII 1996, T Tiunova, 1 male, 1 female imago (reared from larvae); 5 male imagines, 3 larvae; Manoma River, tributary Anjuj River, 12.IX 2001, V Luborez, 3 male imagines; Bikin River, 200 m below motor-car bridge, line Vladivostok - Khabarovsk, 13.VII 2000, T Tiunova, 31 male imagines; same place, 6.VIII 2005, T Tiunova, 19 male imagines; Priokhot’e, Okhota River, 6 km upper mouth, 1–5.VIII 1998, T Tiunova, 1 male imago; Primorskiy Kray: Bikin River, 50 m upper mouth Takhalo River, 1.VII 1995, T Tiunova, 2 male imagines (reared from larvae); Bikin River, Ysenevii Village, 2.VIII 1995, T Tiunova, 2 male imagines; Ussuri River, Stepanovka Village, 3.VII 1988, T Tiunova, 15 male imagines; Ussuri River, 0,5 km upper Arkhipov Stream, 29.VII 1994, T Tiunova, 1 male imago; Ussuri River, 1 km below Utys Mountain, 4.VIII 1994, T Tiunova, 3 male imagines, 1 male subimago (reared from larvae); Ussuri River, Gornie Kluchi Village, 2 km below motor-car bridge, line Vladivostok - Khabarovsk, 18.VII 1996, T Tiunova, 3 male imagines, 3 male and 1 female subimago (reared from larvae), 31 male, 1 female imagines, 5 larvae; same place, 9.VIII 2006, 12 male imagines; Ussuri River, Kamenka Village, 30.VIII 1999, T Tiunova, 21 male imagines; Ussuri River, 3 km upper Koksharovka Village, 31.VII 1999, T Tiunova, 52 male imagines; Ussuri River, about 5 km below mouth Zhuravlevka Village, 1.IX 1999, T Tiunova, 32 male imagines; Kabarga River, tributary of Ussuri River, below motor-car bridge, line Vladivostok - Khabarovsk, 25.VII 2003, T Tiunova, 6 male, 1 female imagines; Bolshaya Ussurka River, 1 km below Zvenigorodka Village, 20.VII 1996, 1 male imago (reared from larvae), 1 male imago, 7 larvae; Malinovka River, 1 km upper motor-car bridge, line Vladivostok - Khabarovsk, 7.VIII 2005, T. Tiunova, 23 male imagines; Basin Sea of Japan, Rasdol’naya River, near Fadeevka Village, 13.VIII 2002, T Tiunova, 2 male imagines; same place, 8.VIII 2005, T Tiunova, 5 male imagines; Suvorovka River, mouth Krivaya River, 23.VIII 2002, T Tiunova, 18 male imagines; same place, 24–25.IX 2002, T Tiunova, 5 male imagines; Medveditza River, tributary Rasdol’naya River, near mouth Kraunovka River, 14–15.VIII 2002, T Tiunova, 1 male imago; Barabashevka River, 16.VIII 2000, T Tiunova, 1 male, 1 female imago (reared from larvae); same place, 3.VIII 2007, T Tiunova, 5 male imagines; Kievka River, 1 km upper motor-car bridge, line Vladivostok - Lazo, 4.X 2009, V Luborez, 17 male imagines. Sakhalin Island: Dagi River, below mouth Malaya Dagi, 16.IX 2009, K Semenchenko, 7 male imagines; Dagi River, middle and below part, 19.IX 2009, K Semenchenko, 13 male imagines.

Description. Male imago (in alcohol). Dimensions: length (mm): body 5.7–7.4; forewings 6.4–8.4; cerci 12.0–18.0. Head: Eyes from dark grey to black with grayish shading; eyes contiguous dorsally. Thorax: mesonotum brown, in general, with two distinct thin, dark longitudinal lines; medioscutum dark brown, submedioscutum gray or light brown with tints of gray, scutellum dark brown (Fig. 24). Length (mm) of foreleg segments: femora 1.5–1.8; tibia 1.9–2.6; tarsal segments 0.2, 0.9–1.3, 0.9–1.4, 0.7–1.1, 0.2–0.4. Abdomen: there are two different types of coloring patterns evident; first: terga 2–7 dark brown and hyaline with a contrasting pattern; lateral sides and anterior margins white, middle portion with a small light pair of spots and strokes; these spots and strokes on terga 5–7 often merge into a large triangular light median spot; second: terga 2–7 being dark brown at their bases and lighter at their lateral sides and middle portion, with the pattern on these being poorly expressed; other terga brown with darker bases. Sterna transparent, grayish, last two segments white, opaque. Forceps and styliger plate brown; penis lobes light brown or yellowish; penis lobes jut slightly out to the edge of the styliger plate; tops of penis lobes rounded externally, inner tooth long and pointed (Fig. 25–26). Latero-dorsoventral teeth on penis lobes are present (Fig. 28–29). Titillators narrow slightly curved and pointed (Fig. 26–27). Cerci: in the proximal third brown, distally from light brown to yellow, base of each segment generally dark brown but sometimes being light brown with the rings on segments being poorly marked.

Female imago. Dimensions: length (mm): 6.0–6.8; forewings 7.7–8.5; cerci 8.5–11.0. Thorax: pronotum and mesonotum brown. All legs white with a dark spot in the middle of the femora. Abdomen: terga colored as in males, but with the pattern on terga expressed with greater contrast, a pair of small light spots and strokes does not merge and is easily visible on terga 2–7. Sterna yellow-tinged grayish. Cerci white, uniformly colored.

Male subimago. Thorax: pronotum light brown; mesonotum white, shaded brownish. Legs white with a dark contrasting spot on the femora. Wings matte, translucent. Abdomen: terga white-tinged grayish, opaque; lateral portion brownish-grey. Sterna white. Cerci white.

Mature larva. Dimensions: length (mm): body 6.0–6.9, cerci 5.0–6.7. Head: forehead brown; posterior part of the head without (Fig. 30) or with a pair of small white spots in the middle area (Fig. 48), similar R. lepnevae. Maxilla with 9 comb-shaped setae at the apical margin (Fig. 33). Thorax: pronotum brown; mesonotum brown with a wide, light median longitudinal stripe. Legs light brown, lighter than the body; femora of all legs with a dark spot in the middle of the light central area; setae on the dorsal surface of forefemora with distinct divergent margins and a rounded apex (Fig. 38). Claws of fore- and middle legs with three subapical denticles (Fig. 40–41). Length (mm) of leg segments are as follows. Foreleg: femur 1.2–1.5, tibia 1.0–1.2, tarsus 0.4–0.6; middle leg: femur 1.2–1.5, tibia 0.9–1.1, tarsus 0.3–0.4; hind leg: femur 1.6–2.3, tibia 1.1–1.4, tarsus 0.3–0.4. Abdomen: terga brown, usually monotonous, terga 2–7 sometimes having a pair of bow-shaped white stripes in the middle area; terga 10 with a pair of white longitudinal spots at the distal margin; central portion of the posterior margin of terga 5 having long and pointed teeth of regular size (Fig. 42); sterna brown, lateral area lighter; sterna 8–9 white with a darker lateral side; abdominal sternum 9 in females with posteromedian emargination (Fig. 39). Gills white, tufted tracheal tubes white or grayish; gill I large, with an even outer margin (Fig. 34); gills III–IV oval with a rounded distal margin (Fig. 35–36), approximately 1.5 times as long as they are wide; gill VII broadens in its middle area (Fig. 37). Cerci white, with the shaded tips.

Distribution and biology. Rhithrogena bajkovae is an East Palaearctic species that is distributed in Transbaikalia (Tshernova et al. 1986), West Siberia (Beketov & Kluge 2003, Beketov 2005), Mongolia (Braasch 1979; Enkhtaivan & Soldán 2009) and the Russian Far East (Sowa 1973, Bajkova 1979, Sinitshenkova 1982, Tiunova & Potikha 2005, Tiunova 2008, 2009) including Sakhalin Island (Tiunova 2007b).

The larvae of this species were found in gravel and pebbles in small rivers or streams and in the middle part of large rivers, which can be characterized as types of rivers that are moderately cold and moderately warm.