Isoperla flavescens Zhiltzova & Potikha 1986

Teslenko, Valentina A. & Zhiltzova, Lidiya A., 2006, Nymphs of the genus Isoperla Banks (Plecoptera, Perlodidae) from the Eastern Palaearctic Region, Zootaxa 1130, pp. 1-33 : 10-13

Isoperla flavescens Zhiltzova & Potikha 1986

( Figs. 22–28)

Description. Nymphs were correlated with adults by rearing from Lasovka River. Length of mature male nymph 9.0– 9.6 mm, female 10.0– 13.5 mm; cerci of male nymph 4.0– 4.5 mm; female 5.0–6.0 mm. General body color brownish­yellow; labrum, frontoclypeus and anterior part of the head dark brown; body yellowish ventrally, top of the abdomen slightly brownish. Clothing hairs on body surface dark and numerous.

Head with occipital spinule row irregular and interrupted medially; color dark­brown in anterior half ( Fig. 22), with sharp yellowish M­line; thin transverse, light stripe on the frontoclypeus not always distinct; two light, oval spots posterior to anterior edge of frontoclypeus; interocellar area with an indistinct pale triangle; area along epicranial suture pale; occiput pale, with 2 indistinct spots forward of occipital suture. Lacinia bidentate ( Fig. 23), 6–7 stout, dark setae below subapical tooth, followed by thin setae to base. Tip of galea reaches the base of subapical tooth ( Fig. 23). Mandible ( Fig. 24) similar to other species.

Thorax. Pronotum ( Fig. 22) transverse­oval, fringed with short setae, occasional long hairs interspersed at anterior angles, lateral and posterior pronotal margins; light median spot close to anterior pronotal margin indistinct; lateral pronotal margins light; anterior and posterior margins and sublateral fields brownish. Meso­ and metanotum wing pad bases slightly darker than lateral margins and median area. Legs light­brownish ( Fig. 25), with dense fringe of silky hairs along outer margin of tarsi, femora, and tibiae.

Abdominal terga ( Fig. 22) with thin brown stripe medially surrounded by pale stripe, lateral tergal margins brownish; posterior tergal margins with fringe of long setae, intercalary bristles numerous. Cerci yellowish ( Figs. 26–28), apical half with dorsal fringe of long silky hairs; length of these hairs exceeds the length of corresponding cercal segment in the apical third; one dorsal and one ventral seta in apical whorl longer than others, their length exceeds one half length of corresponding cercal segment.

Material examined: Russia. Primorsky Region, Lazovka R., below the pass, rearing 13.VI 1998, V. Teslenko, 4 nymphs; Komissarovka R., 11.VI 1988, V. Teslenko 1 nymph; Ussuri R., 29.V 1992, T. Tiunova, 1 nymph; Yedinka R., 9.VII 1985, E. Postnikova, 11 nymphs; Khabarovsky Region: Sukpai R., 22.VI 1998, V. Teslenko, 2 nymphs; Tumnin R., 17.06. 1997, T. Tiunova, 1 nymph.

Distribution. Russia: Primorsky and Khabarovsky Regions; South Korea.