Isoperla eximia Zapekina-Dulkeit, 1975

Judson, Sarah W. & Nelson, C. Riley, 2012, 3541, Zootaxa 3541, pp. 1-118 : 47

Isoperla eximia Zapekina-Dulkeit, 1975

SYNONYMY

Isoperla eximia Zapekina-Dulkeit, 1975

TYPE LOCALITY: Russia .

DIAGNOSIS: Adults have a large, quadrate, brown pigmented area over the interocellar region and extending posteriorly to the occiput ( Fig. 321). No light interocellar spot is present in contrast to the majority of Mongolian Isoperla . The pronotum has a wide, pale stripe and sublateral darkened areas with a pale pronotal margin. The coloration is most similar to that of I. altaica ( Fig. 311). Isoperla eximia can be distinguished from I. altaica because it lacks the transverse line of dark pigmentation seemingly connecting the eyes posteriorally ( Fig. 321) which is present in I. altaica ( Fig. 311). The male has a distinctive large penial sclerite that, like I. altaica , is asymmetrical in the caudal view ( Fig. 323) in contrast to I. lunigera which has a symmetrical sclerite ( Fig. 333). In I. eximia , the penial sclerite is narrow at the base, and as such, is of relatively uniform length for the basal two thirds of the sclerite, as opposed to I. altaica which is abruptly wider at the base ( Fig. 313). The penial sclerite lacks ( Fig. 323) the twisted crest present in I. altaica ( Fig. 313). The female subgenital plate is barely produced over sternum 9 ( Fig. 324) and is not diagnostic. Coloration can be used to distinguish females from I. altaica and other Isoperl a with short plates, specifically I. asiatica , I.mongolica , and I. potanini . Despite strong similarities between adult forms, the nymph is quite distinct from I. altaica , with a pronounced longitudinal stripe coloration pattern ( Fig. 304).

DISTRIBUTION—Global: East Palearctic— Regional: AOB— Aimag: SE.

DISCUSSION: This species is often found sympatrically with I. altaica , as was the case with the only two localities at which we collected I. eximia , where in both cases we simultaneously documented I. altaica . The first records of this species from Mongolia are recent, collected in 2003 and published in Zwick and Surenkholoo (2005).