Isoperla altaica Šamal, 1939

Judson, Sarah W. & Nelson, C. Riley, 2012, 3541, Zootaxa 3541, pp. 1-118 : 46

Isoperla altaica Šamal, 1939

SYNONYMY

Isoperla altaica Šámal, 1939

TYPE LOCALITY: Russia: River Karas , outflow of Lake Kara-Koli .

DIAGNOSIS: The head of adults has a large, dark, quadrate spot covering the interocellar area with pigment anterior to it extending as an M-shaped line between the antennal bases ( Fig. 311), This coloration is similar to I. eximia Zapekina-Dulkeit, 1957 ( Fig. 321) but distinct from all other Mongolian Isoperla which have a pale interocellar spot that is either open or closed posteriorly or, if the interocular area is dark, the additional pigment posterior to the interocellar area is lacking. Isoperla altaica can be distinguished from I. eximia by the presence of dark pigmentation extending from the posterior of the interoccellar region towards the eyes ( Fig. 311) and by darker overall coloration, particularly on the mesoscutum ( Fig. 311). Males have a distinctive large penial sclerite that, like I. eximia , is asymmetrical in the caudal view, in contrast to I. lunigera which has a symmetrical sclerite ( Fig. 333). In I. altaica , the penial sclerite is wide at the base and twisted into a crest at the apex ( Fig. 313), in contrast to I. eximia which has a narrow and uncrested sclerite ( Fig. 323). The female subgenital plate is a broadly rounded and barely produced over segment 9 ( Fig. 314), but not particularly distinctive. Coloration can be used to distinguish females from I. eximia and other Isoperla with short plates, specifically I. asiatica Šamal, 1939 , I.mongolica Zhiltzova, 1972 , and I. potanini . Nymphs are superficially similar in coloration to I. lunigera , with the majority of the head darkly pigmented, especially in the ocellar region, and with pale areas near the eyes and center of the clypeus ( Fig. 302). In addition, I. altaica has a longitudinal row of isolated pale circles on each thoracic segment, present on both sides of a pale median stripe.

DISTRIBUTION—Global: Altai mountains— Regional: AOB, IDB— Aimag: AR^, BO^, KhD, KhG^, SE, TO^, UV.

DISCUSSION: Isoperla altaica often occurs sympatrically with the morphologically similar I. eximia , although we more commonly encountered I. altaica in our study. This species was first recorded from Mongolia by Zhiltzova (1975).