Nemoura jejudoensis Zwick & Baumann 2011

(Figs.1–12)

Zwick & Baumann 2011:149 (original description of the male and female) Material examined. Russian Far East, Primorskyi Region: 10 males, 7 females, 15 nymphs, Vladivostok, Rybachyi Sett., Meortvaya Pad Stream, N 42°080.417’ E132°021.346’, 28.07.− 16.08.2015, rearing, coll. Teslenko V .; Khabarovskyi Region: 6 males, 26 females, Fedotkin Spring, Bira R. Basin, Amur R. Basin, N 48º38.446’ E131º37.183’, 17.09.2015, coll. Makarchenko Eu .

Description. Males of N. jejudoensis of the Russian Far Eastern (RFE) specimens agree well with original description and excellent illustrations by Zwick and Baumann (2011). The RFE males show slight variations as compared to Korean specimens in number of teeth on the prong of the epiproct. Zwick & Baumann (2011) mentioned that each turned claw-like plate (prong) has four marginal bare teeth (figs. 1, 2 in Zwick & Baumann 2011). Sometimes in RFE males, the number of teeth on the prong may vary from three to five (Fig. 1).

Mature larva (Figs. 2−12). Body relatively stoUt, the body length 5.3–7.0 mm in males; 6.0–7.0 mm in females. General color brown with a dark brown pattern (Fig. 3). Head stout with dark brown tentorial callosities connected with a dark brown interocellar patch slightly extended sideways beyond each posterior ocellus; a small black longitudinal line between lateral ocelli medially (Figs. 2, 3). Occiput distinctly paler than middle of head due to a pair of small pale patches near epicranial stem, the epicranial arms also pale (Fig. 3). Antenna pale, scape, pedicel, and apical antennal segments dark brown. Pronotum trapezoidal, approximately 1.5 X wider than long, light brown, slightly narrowed towards the posterior margin; corners rounded. Pattern on the pronotum diffuse, consisting of small dark brown spots that form an X-shaped figure with rounded anterior and posterior branches and transversal medial line of spots (Figs. 2, 3). Mesonotum and metanotum with V-shaped dark brown pattern anteromedially, dissected by finger-like light brown patches; the posterior margins are dark brown. Legs pale. Femora with an apical diffuse dark ring, semi-oval pale patch close to inner edge basally, more pronounced on the fore leg, than on hind leg (Figs. 3, 7). The fore femur 2.3 X longer than wide and the hind femur about 2.5−2.9 X longer than wide. Abdomen relatively slender, integument light, matte in appearance, terga brown. Rows of dark brown small patches on terga II-VI form three longitudinal bands, a mesal and two lateral bands (Figs. 2, 3). Lateral longitudinal bands sometimes missing on terga 7–10; medial longitudinal band continue to tergum 10 and interrupted by pale patch on terga 7–10 medioposteriorly. Ventral surface pale with brown patches medially and laterally. Cerci pale with approximately 23 segments slightly darkened distally, length equals approximately 65% of body length, edges of basal and middle segments nearly parallel laterally (Figs. 9−12).

Chaetotaxy distinctive, sometimes black in color, especially on the legs (Fig. 3). Dorsally, head with fine procumbent setae and dense tiny oval setae with apex narrowed to a short point; small acute setae occur on occipital margin. Antennal segments with short and sharp setae. Setal fringe around the pronotum wavy and consists of setae of the different lengths (Fig. 5) and configuration: relatively short stout oval, irregularly notched bristles present on anterior and posterior margins medially (Fig. 4); long irregularly notched bristles narrowed apically occupy the lateral margins sporadically (Fig. 5). The longest bristles are observed mostly at anterior and posterior pronotal corners, where the longest bristles alternate with shorter ones and form an undulate fringe (Fig. 5). Few of the longest bristles at the posterior corners, the length of the longest bristles approximately equals 6.0−6.3% of pronotUm width. The pronotUm disc with tiny oval setae, narrowed to a short acUte apex; with small irregularly notched setae, fine procumbent setae, and occasional long hairs (Figs. 4, 5). The outer wing pad margin covered with acute bristles (Fig. 6). Tiny oval setae with apex narrowed to a short point in the lines on wing-pads same type as head and pronotum (Fig. 6). Legs with markedly heterogeneous chaetotaxy (Fig. 7). Setal fringe on outer femur margin starts from ⅔ of its length. All femora with fine procumbent setae, short and long spine-like bristles and occasionally with thin long hairs (Fig. 7). Long spine-like bristles occur in the apical half in an irregular arrangement (Fig. 7). The longest spine-like bristles reach 40% of the width of femur on fore leg and 27% of the hind leg. A conspicuous bald median line on the dorsal surface of all femora, covered with rounded scales. An apical row of short setae on all femora. Tibia with sporadic fine procumbent setae, dense and strong spine-like bristles along the outer and inner edges; the bristles not longer than width of tibia (Fig. 7). Tarsi covered with thin hairs; tibial spurs short. Terga covered with short acute bristles and fine procumbent setae. The posterior terga margins feature mostly short acute bristles and two pairs of conspicuous long slightly curved spine-like bristles: lateral bristle pair much longer than central pair (Fig. 8), length of the longest bristles on terga 5−6 reaches 45% length of segment (Fig. 8). Cercal segments with an apical whorl of bristles and a few short and tiny intercalary setae, intercalary setation sparse (Figs. 10−12). The apical whorl comprises a set of short, oval bristles with rounded apex, a few thin hairs mixed with long, acute bristles; their number does not exceed 8 in the basal and middle cercal segments (Figs. 10−11). The longest bristles reach 77% of the segment’s length at cercal segments 14−16 (Fig. 11).

Diagnosis. Setal fringe on pronotum of variable length, slightly irregular, comprises stout irregularly notched bristles and oval bristles with apex narrowed to a short point, the bristles on anterior and posterior pronotal corners longer than rest, and the length of the longest bristles reach 6.3% of pronotum width. Long spine-like bristles on femora in irregular arrangement; the longest bristles reach 40% of the femur’s width on the fore leg. Paired spinelike bristles on terga 5−6 margins reach 45% the length of segment, other bristles much finer and spaced, sparse. Tiny intercalary setae on cercal segments sparse, the apical whorl comprises not more than 8 long, acute bristles, the longest bristles reach 77% of length of segment at cercal segments 14−16.

Nemoura jejudoensis and N. geei Wu, 1929 are closely related species. Adults are extremely similar, separable only in the details of the epiproct (Zwick & Baumann 2011). The larvae of the both species are also very similar, especially in the pattern of the abdomen (Murányi & Park 2011). Both species belong to the N. ovocercia group (Baumann 1975, Shimizu 1997, Zwick & Baumann 2011). The larvae of this group can be separated from other species of Nemoura by three dark longitudinal bands (a mesal and two lateral bands) on abdominal terga 2–8 or 9. The bands are distinctive in mature nymphs and most teneral adults, but they are sometimes indistinct (Shimizu 1997). In addition to body pattern, both species have similar chaetotaxy on legs, posterior margin of the abdomen and cerci. The pronotal fringe of N. jejudoensis is also very similar to N. geei but has not been described in detail.

Distribution. The type locality of N. jejudoensis is the waterfalls near Seogwipo City on Jeju Island, South Korea, situated in the Korea Strait between the Sea of Japan and the South China Sea. The species was collected in December. The RFE specimens of N. jejudoensis were found in the small tributary stream of the Amur River Basin and streams flowing into the Sea of Japan in the vicinity of Vladivostok. Adult flight period extended from July to August. Single females were found until November. Presently, the distribution of N. jejudoensis may include forested streams on the southern mainland coast of the Sea of Japan.