Isoperla sejila Cao & Wang & Li 2020, sp. nov.
Creators: name: Cao, Zhishan
name: Wang, Ying
name: Li, Weihai
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Plecoptera
Perlodidae
Isoperla
Isoperla sejila

description: Isoperla sejila sp. nov.
Adult habitus. (Figs. 1–3). Body generally brown to dark brown. Wings macropterous with both macropterous and brachypterous females (Fig. 1). Wings hyaline with brown veins. Forewing: five crossveins between the C and Sc veins, more R veins and more m-cu crossvines. Hindwing with four crossveins between C and Sc veins, M veins with four branches, Anal field large, and with more A veins. (Fig. 2). Head slightly wider than pronotum, with a rounded pale spot occurring between the two posterior ocelli. M-line dark brown. Three pale ocelli, posterior pair larger. Antennae and palpi dark brown. Pronotum rectangular, wider than long, with darkly sclerotized anterior and posterior margins. Rugosities dark, two yellow brown longitudinal stripes bordering the sclerotized median suture. The mesosternal Y-arms approach posterior corners of furcal pits. Legs yellow brown to brown. Cerci slender and brown, with 18 segments, the distal three dark brown, and the ventromedial of segments 6-18 each with a long seta (Fig. 3).
Male. (Figs. 3–6). Body length ca. 11 mm. Forewing length ca. 10 mm, hindwing length ca. 9 mm. Tergum 10 with posterolateral stronger and longer setae. Sterna 6-8 sometimes with some dark transverse bands near the posterior margins. Sternum 9 extended posteriorly and covering nearly the entire length of sternum 10. Paraprocts weakly sclerotized, bases broad gradually tapering to points, apexes slightly hooked with long setae on the ventroposterior margin. Everted aedeagus completely membranous, cylindrical in-shaped, the apex rounded and inflated. The dorsal surface covered with small, stout and sharp spinules (Fig. 6d), mixed with some sensilla, each with a single microtrichia (Fig. 6e).
Female. (Figs. 1, 7). Macropterous individuals, body length ca. 12 mm. Forewing length ca. 12 mm, hindwing length ca. 11 mm. Brachypterous individuals, body length ca. 11 mm, the forewing length ca. 7 mm, hindwing length ca. 5 mm. Terga 6–9 with two dark spots median and some irregular-shaped dark spots occurring near the lateral margins. Tergum 10 similar to male. Subgenital plate subtriangular-shaped, sometimes medially slightly concave, broadly produced, covering nearly ⅓ of sternum 9, with a dark median stripe. Margin of subgenital plate not deflected ventrally near apex. Paraprocts triangularly-shaped and covered with setae.
Egg. (Fig. 8). Available eggs dissected from several females were apparently not mature. Elliptical in the lateral view. Chorion totally pale, ca. 0.34 mm long and 0.22 mm wide (n=8). Collar ring-shaped, rim irregular. Chorion surface pited.
Type material. Holotype male (CAU), China: Tibet Autonomous Region, Nyingchi City, Nyingchi Coun- ty, Sejilashan (Sejila Mountains), Sejilashan National Natural Reserve, unnamed stream at Zhongshan Station, 29°36.60'N, 94°36.19'E, 4033 m, 5.VI.–VII.2017 and 5.VII.–VIII.2017, Q.C. Yang. Paratypes: 35 males and 50 females (CAU & HIST), same locality and data as holotype.
Distribution. Presently only known from the Sejila Mountains National Nature Reserve, Nyingchi (Linzhi) of the Tibet Autonomous Region, China.
Etymology. The species refers to the type locality, Sejila Mountains, Tibet Autonomous Region of southwestern, China.
Remarks. The adult male of the genus Isoperla is usually characterized by a vesicle on sternum 8 (Chen 2018), but in several species the vesicle is reduced or obsolescent. The vesicle of I. sejila is obsolescent. Other Chinese species apparently lacking a developed vesicle includes I. neimongolica (see fig. 4 in Yang & Yang 1996), but in I. neimongolica the apex of the extended ninth male sternum is trapezoidal, and the posterior margin truncate, separating the two taxa. Additionally, dorsally, the head of I. sejila has a pale and rounded spot, whereas I. neimongolica has a butterfly-shaped patch connecting the ocelli. It is unknown if the male of I. lunigera (Klapálek, 1923) possesses a vesicle, but the paraproct of this species is obviously hooked and the aedeagus has a sclerite. The male of I. sejila lacks aedeagal sclerites and the paraprocts are slightly hooked (see figs. 183–188 in Teslenko & Zhiltzova 2009 and figs. 332–333 in Judson & Nelson 2012). The males of I. fengi Wu & Claassen, 1934, I. sowerbyi Wu & Claassen, 1934, and I. bimaculata Yang & Yang, 1996 are still unknown, and original material was collected many years ago and no recently collected specimens are available for study (Chen et al. 2019). However, females of these three species can be distinguished from I. sejila. The subgenital plate of I. fengi is produced over the entire sternum 9 and has a uniform medial posterior emargination, whereas the subgenital plate of I. sejila is produced 1/3 of stermun 9, sometimes with a small posterior emargination. The female of I. bimaculata is characterized by the sternum 9 that divided into two parts, I. sejila lacks this character. The subgenital of I. sowerbyi is more rounded and produced more than half of sternum 9, whereas the subgenital of I. sejila is subtriangular and shorter.
description: Published as part of Cao, Zhishan, Wang, Ying & Li, Weihai, 2020, A new species of Isoperla (Plecoptera: Perlodidae) from China, pp. 251-260 in Zootaxa 4858 (2) on pages 252-254, DOI: 10.11646/zootaxa.4858.2.6, http://zenodo.org/record/4411821