Isoperla mongolica Zhiltzova 1972

(Figs.49–53)

Description. Nymphs were correlated with adults according to theirs presents in collecting place in the same time. Length of mature male nymph 8.0–10.0 mm, female 10.0– 12.8 mm; cerci incomplete General body color pale­brown (Fig. 49). Ventral body side yellowish.

Head with occipital spinule row interrupted medially; brown band between antennal bases; interocellar area pale and closed (Fig. 49); pale spot anterior to anterior ocellus almost closed by thin transverse, dark stripe; lateral and anterior margins of frontoclypeus pale; labrum brown with small pale spot medially; occiput with dark, indistinct, and complicated banding and spotting. Lacinia bidentate (Fig. 50), triangular, with slight subapical projection, inner lacinial margin with four stout setae and a row of 10–12 short thin setae below subapical projection; tip of galea reaches the subapical tooth base.

Thorax. Pronotum (Fig. 49) fringed with short, thin setae, these prolonged on posterior pronotal margin; medial stripe pale except for short, dark band medially; lateral margins pale, anterior and posterior margins darkened, lateral fields brownish with indistinct light pattern. Meso­ and metanotum (Fig. 49) with pale complicated pattern; wing pads with longitudinal dark stripe medially and light margins. Legs yellowish (Fig.49); tibiae with fringe of silky swimming hairs, femora with only short hairs. Abdominal terga (Fig. 49) brownish, with paired pale spots surrounding a brown median stripe, lateral margins entirely pale or with pale spots, posterior edge of terga margined with thick, long fringe of setae. Tenth tergum with large pale heart­shaped spot medially. Cerci (Figs. 51–53) pale yellow, with dorsal silky fringe hairs; in apical part apical whorls with short setae and one ventral seta longer than others, its length not exceeding half the length of its corresponding segment.

Material examined: Mongolia. Turgol R., Hovsgol Lake Basin, 25.VIII 1988, K. Varykhanova, 2 nymphs.

Distribution. Russia: Sayan, Altai Mnts.; Mongolia.