﻿A new species of Suwallia Ricker, 1943 (Plecoptera, Chloroperlidae) from southwestern China, with an updated key to male Suwallia species

﻿Abstract A new species of the genus Suwallia Ricker, 1943 (Plecoptera, Chloroperlidae), Suwalliadengbasp. nov., is described from Tibet and Yunnan, southwestern China. A diagnosis and description of the adult habitus and aedeagal structure are illustrated with color images. Similarities in the terminalia with closely related species are discussed. In addition, an updated key to adult males of the Suwallia species of China is provided.

The genus Suwallia Ricker, 1943 belongs to tribe Suwalliini Surdick, 1985 of the subfamily Chloroperlinae. It is distributed in the East Palearctic and Nearctic regions (DeWalt et al. 2021). Most species of the genus Suwallia were revised and recorded by Alexander and Stewart (1999). Suwallia is mainly distributed in Russia, Mongolia, Japan, and North America (Alexander and Stewart 1999;Teslenko and Zhiltzova 2009;Judson and Nelson 2012). In China, the first species of Suwallia was reported by Li et al. (2015a), and until now seven species of this genus had been reported for the country: Suwallia errata Li & Li, 2021, Suwallia decolorata Zhiltzova & Levanidova, 1978, and Suwallia talalajensis Zhiltzova, 1976 were reported by Li et al. (2015a, b) and Li et al. (2021) from the Inner Mongolia Autonomous Region, northern China (Fig. 7), whereas Suwallia wolongshana Du & Chen, 2015 and Suwallia jihuae Chen, 2019 were reported by Chen and Du (2015) and Chen (2019) from the Sichuan Province of southwestern China. Recently, Suwallia kuandian Shi, Wang & Li, 2022 and Suwallia asiatica Zhiltzova & Levanidova, 1978 were reported by Shi et al. (2022) from Liaoning Province, northeastern China. In the current paper, a new species of Suwallia is described from Tibet and the Yunnan Province of southwestern China. This is the first record of the Suwallia genus from both regions. Tibet is also known as Xizang in Chinese and is positioned on the Tibetan plateau, known as the world's highest and largest plateau. The Yunnan Province lies adjacent to the Tibet, Sichuan, Guizhou, and Guangxi provinces of China and borders with Myanmar, Laos, and Vietnam. The taxonomy of the new species is discussed, a distributional map, and a key to the known species of Suwallia from China are provided.

Materials and methods
All specimens were collected by aerial net or hands and preserved in 75% ethanol. Terminalia were examined and illustrated by KEYENCE VHX-5000 and the final images were prepared using Adobe Photoshop CS6. The type specimens of the new species were placed in the insect collection of Yangzhou University (ICYZU), Jiangsu Province, China. Data for the key and distribution map were extracted from the published literature (Chen and Du 2015;Li et al. 2015a, b;Chen 2019;Shi et al. 2022). Diagnosis. The new species is characterized by the sclerotized median sclerite of tergum X and its aedeagus armature. The shape of the median sclerite of tergum X resembles a turtle or a hexagonal star. The aedeagus, with a large distinct sclerite divided into an eagle-shaped trifurcate structure, the large median sclerite, and one pair of wing-shaped lateral sclerites on both sides, is diagnostic (Figs 2-4).
Female. Adult habitus (Fig. 1B). Body length 9.0-10 mm (N = 10), forewing length 7.5-8.5 mm, hindwing length 6.5-7.5 mm. General body color, shape and appearance similar to those of male. Head and pronotum similar. Dorsal segment of abdomen with trapezoidal dark brown stripe extended to sternum VIII, subgenital plate large, extending to posterior portion of sternum IX, constricted from base, expanded medially, then slightly tapering toward posterior margins. Subgenital plate covered with minute, fine hairs. Tergum X not produced posteriorly. Paraproct in the shape of a small triangle, bearing small hairs (Fig. 5A-C).
Egg and nymph. Unknown.

Distribution. Southwestern China (Tibet and Yunnan Province).
Etymology. The species is named after the type locality, Dengba village.

Remarks.
The new species is closely related to Suwallia talalajensis, but can be distinguished by the sclerotized portion between the hemitergal processes, the   pigmentation of tergum IX, the armature of the aedeagus and the well-developed, membranous, knob-like epiproct. Suwallia talalajensis does not have a distinct aedeagal sclerite (Li et al. 2015b: fig. 5), whereas the new species has a distinct sclerite (Figs 4A-D, 6B). Tergum IX of the new species is covered with abundant, thick hairs, and its body pigmentation is different from that of Suwallia talalajensis. The new species also shows similar characteristics to Suwallia errata (Li et al. 2021), but it can be easily differentiated by the sclerotized portion between the hemitergal process and the shape of the aedeagus. Suwallia errata has a V-shaped aedeagal sclerite (Li et al. 2015a: figs 1-6), but the new species has the aedeagal sclerite of a different shape. The new species lives in fast-flowing rivers (width = 5 m), where a large gravel substrate is present. The adults occur on leaves of trees or shrubs near the river (Fig. 8).  Tergum X median sclerite turtle-like, aedeagus membranous, without distinct armature or sclerite (see Li et al. 2015b: fig. 2) ... Suwallia talalajensis -Tergum X median sclerite hexagonal star-shaped, pointed posteriorly, aedeagus with distinct trifurcate sclerite (Figs 2-4) ........Suwallia dengba sp. nov.