Nemoura ussuriensis Zhiltzova, 1997 in Teslenko & Zhiltzova, 1997

Teslenko, Valentina A., 2016, Larvae of two East-Asian species of Nemoura (Plecoptera: Nemouridae), Zootaxa 4162 (2), pp. 381-390 : 386-388

Nemoura ussuriensis Zhiltzova, 1997 in Teslenko & Zhiltzova, 1997

( Figs. 13−23 ).

Material examined. Russian Far East, Primorsky Region: 4 mature larvae of males, Anan’evka River , Razdol’naya River . Basin, near road bridge, at Venevitinovo Sett., N 43º24.476’ E131º44.302’, 27.04.2004, coll. I. Tiunov ; 2 larvae of females, Vtoraya Rechka River, Razdol’naya River . Basin, near road bridge, 3.05.2013, coll. I. Tiunov ; 1 mature male larva, Gladkaya River , near Gvozdevo Sett., 26.04.2013, coll. I. Tiunov .

Mature larva. Mature larvae are large, body length 7.2–7.7 mm in males; 8.3–9.6 mm in females. General color brown with conspicuous head pattern: tentorial callosities brown, contoured by narrow dark bands extending to the clypeus, resembling the Russian letter П with mesal notch; clypeus with prominent rounded anterior corners. The interocellar area bears a diffuse dark spot attaining the posterior ocelli ( Figs. 13, 14 ). Occiput with three pairs of pale spots surrounded by thread-like brown loops, posterior margin darkened. Antenna brown, long, up to 85−100% of body length, scape paler than both head or pedicle and flagellum. Pronotum approximately 1.5 X wider than long, pattern indistinct, with small dark brown spots together resembling the letter Х ( Figs. 13, 14 ). Mesonotum and metanotum with U-shaped brown band and diffuse pale patch anteromedially. Legs brown, outer margin of femora darker than inner, the fore femur is 2.6 X longer than wide ( Fig. 18 ), the hind femur 3.3 X longer than wide, hind legs are long. Abdomen relatively slender, integument light, matte in appearance, terga brown with a mesal row of dark brown patches which forms a longitudinal band on 1−8 segments ( Figs. 13, 14 ). Cerci pale, strongly hairy, long, with 31−32 segments, length reaches 100−118% of body length ( Figs. 13, 14 , 20 ).

Setation distinct. Setal fringe around the pronotum consisting of occasional long hairs, and cylindrical bristles, the apices rounded and often slightly wider than the base; length of bristles on lateral margins and anterior and posterior corners greater than on anterior and posterior margins; fringe on lateral pronotal margins relatively regular and denser than on anterior and posterior margins, because of bristles stand in two or three rows ( Figs. 15, 16 ). Length of the longest cylindrical bristles at the anterior and posterior pronotal corners reaches 3.4% of pronotal width. Pronotal disc with occasional long hairs, short cylindrical setae and tiny procumbent setae with short acute hooked apices. These tiny setae are concentrated on the lateral fields of pronotum ( Fig. 16 ). Outer wing pad margin covered with slender club-shaped bristles, and occasional long hairs; cylindrical setae and occasional long hairs in the lines on the wing-pads ( Fig. 17 ). All femora bear fine numerous procumbent setae and dense short blunt bristles. Setal fringe on the outer femur margin short, including a few long thin hairs and short blunt bristles in irregular arrangement ( Fig. 18 ); the longest bristle reaches approximately 22% of femur width on the fore leg and 20% on the hind leg. Setation of tibia and tarsi very similar to femur. Terga covered mainly with short cylindrical bristles and sparse tiny procumbent setae ( Fig. 19 ). Setae along the posterior tergal margin heterogeneous: most apically rounded cylindrical bristles are relatively short ( Fig. 19 ), while one conspicuous pair of long bristles turns apically into fine, thin hairs that are easily overlooked; on the posterior margin of terga 5−6 hairs reach 47% of segment length ( Figs. 19, 23 ). Cerci densely covered with acute bristles of different length: in apical whorl on basal cercal segments the bristles shorter the segment; on cercal segment 8 the longest acute bristles reach 148% of segment’s length, intercalary setation visible ( Fig. 21 ); in cercal segments 16–17 the longest bristles do not exceed 95% of segment length, the intercalary setae reach 128% of the segment’s length ( Fig. 22 ). Setal ring of apical cercal segments sparse, intercalary hairs noticeable. Additionally to the long thin acute bristles there are tiny setae with rounded apex and a few thin long hairs in the apical whorl.

Diagnosis. The larvae of N. ussuriensis can be easily distinguished from the known larvae of Nemoura in the RFE by the head pattern, long and the “fuzzy-like” appearance of the cerci exceeding the body length with distinctive setation. Setal fringe around pronotum, outer wing pad margin and posterior tergal margins consisting of cylindrical bristles with apices rounded and often a little wider than the base, but not club-shaped. Fringe on lateral pronotal margins regular and dense, cylindrical bristles placed in two or three rows, tiny procumbent setae on pronotal lateral fields with short acute hooked apexes. The outer femur margin bears bristles of another type, they are short and blunt. The posterior tergal margins 5–6 feature conspicuous paired long, thin cylindrical bristles (like hairs) reaching 47% of the length of segment ( Figs. 19, 23 ) among the mostly short cylindrical bristles. Cerci have homogeneous setation of long acute bristles. In the apical whorl of cercal segment 8 the longest acute bristles reach 148% of the segment’s length, intercalary setation visible; in apical whorl of 16−17 cercal segments the longest acute bristles do not exceed 95% of the segment’s length and the longest intercalary setae reach 128% of the segment’s length.

Distribution. Nemoura ussuriensis is currently considered an East Asian mainland endemic species with a restricted distribution south of Primorsky Region of the RFE in the Razdol’naya River Basin and small salmon streams flowing into Peter the Great Bay of the Sea of Japan ( Teslenko & Zhiltzova 2009). Zwick (2010) has suggested that the description of the Korean species, N. espera Ham & Lee, 1999 is very similar to N. ussuriensis and may be a junior synonym. Certainly, this suggestion requires further study of comparative material. However, it seems that N. ussuriensis should be encountered in streams of China and the Korean Peninsula, because the transboundary Razdol’naya River flows through China and Russia, and small salmon streams originate in the spurs of the Black Mountains of the Changbai Mountain Range shared with China and Korea Pennisula. The flight period extended from the end of April to the beginning of June.

Figures

FIGURES 13 – 14. Larva of Nemoura ussuriensis, habitus, dorsal view, not to scale.

FIGURE 15 – 18. Larva of Nemoura ussuriensis. 15. Cylindrical bristles with rounded apices on anterior margin of pronotum. 16. Chaetotaxy on disc, right anterior pronotal corner and lateral margin with dense cylindrical bristles. 17. Cylindrical and club-shaped bristles on outer margin and in the rows on wing pad. 18. Right fore leg. Scale (mm): 15 – 17 = 0.1; 18 = 0.3.

FIGURES 19 – 23. Larva of Nemoura ussuriensis. 19. Chaetotaxy of terga 5 – 6. 20. Left cercus. 21. Cercus segments 8 − 11 with acute bristles in whorl cercus and acute intercalary bristles. 22. Cercus segments 16 & 17 with long, acute bristles in cercus whorl and intercalary bristles. 23. Cylindrical bristles and one of the paired long slightly curved thin bristle on the posterior margin of terga 5 − 6. Scale (mm): 19, 21, 22 = 0.1; 20 = 0.3; 23 = 0.05.