Two new species of Nemouridae (Insecta: Plecoptera) from China

Nemoura Latreille, 1796 and Amphinemura Ris, 1902 are the two largest genera of Nemouridae in China. In this paper, two new species are described and illustrated from China: Nemoura lixiana sp. nov. from Sichuan Province and Amphinemura jiaoheensis sp. nov. from Jilin Province. The two new species are diagnostic from congeners by the genitalic structures in males and females.


Introduction
The nemourid genus Nemoura Latreille, 1796 contains over 190 valid species distributed in the Holarctic and Oriental regions (Baumann 1975;DeWalt et al. 2020). Nemoura is the second largest genus of Nemouridae in China, with 40 species described. Most recent contributions to Nemoura from China have been made by Yang et al. (2015), Chen & Du (2017a, Qian et al. (2018) and Mo et al. (2020).
Another nemourid genus, Amphinemura Ris, 1902, is also a large genus, including over 200 valid species from the Holarctic and Oriental regions (Baumann 1975;DeWalt et al. 2020). In China, Amphinemura is the largest genus of Nemouridae, with 92 known species. Recent contributions to Amphinemura include Yang et al. (2015), Li et al. (2016Li et al. ( , 2017aLi et al. ( , 2017bLi et al. ( , 2018aLi et al. ( , 1028b and Mo et al. (2017Mo et al. ( , 2019. The present contribution is devoted to the description of two new species of Nemoura and Amphinemura from Sichuan Province of western China and Jilin Province of northeastern China, respectively (Fig. 1).

Material and methods
Specimens used in this study were collected by hand and preserved in 75% ethanol. Abdomens of the males were cleared in 10% NaOH. Observations and measurements were performed with a SDPTOP SZM45 stereo microscope. Color images were taken using a Canon EOS 6D digital camera with a Canon MP-E 65 mm 5× macro lens and optimized with Adobe Photoshop CS6. All pictures were adjusted and assembled into plates with Adobe Photoshop CS6. Holotypes and paratypes are deposited in the Insect Collection of Jiangsu University of Science and Technology, Jiangsu Province, China (ICJUST).

Abbreviations
The following

Diagnosis Adult
Cervical gills absent but with single small membranous, gill-like nubs outside of lateral cervical sclerites.

Male
Paraprocts divided into 2 lobes; inner lobe short and narrow; outer lobe sclerotized ventrally and membranous dorsally, very large and triangular or elongate in shape. Cerci mostly sclerotized, lateral sclerotized strip usually terminates at apex in 1 to 3 spines or hooks. Dorsal sclerite of epiproct large and broad at base, mostly darkly sclerotized, extending dorsolaterally, narrower around lateral knobs and then very large, usually completely covering lateral aspects of epiproct and part of ventral aspect, anterior area usually lightly sclerotized; ventral sclerite darkly sclerotized, broad at base, with lateral knobs at basolateral corners, tapering toward apex, forming parallel ridges, one on each side of midline, usually covered by dorsal sclerite near tip of epiproct, extending inward and upward to dorsal surface, visible portion paired and quite variable in shape, often bearing spines or hooks.

Female
Sternum 7 enlarged and extended posteriorly, covering part or all of sternum 8, produced area sclerotized. Sternum 8 narrow and mostly membranous, with small sclerotized area at genital opening. Cerci mostly sclerotized.  Fig. 1), which is apparently isolated from the known 'northeastern Asian' distribution of N. geei in Beijing, Henan, Shandong, Inner Mongolia, Korea, Japan and the Russian Far East (Yang et al. 2015;DeWalt et al. 2020).

Etymology
The new species is named after the type locality, Lixian County.
abdomen (Figs 2-4). Abdominal segments generally pale brown; abdominal terga with an obscure longitudinal stripe. Posterior margin of tergum 9 with a row of long bristles. Tergum 10 with a membranous median area anterior of median area, with two small lateral patches of sensilla basiconica; posterior margin of tergum 10 with two sclerotized coniform lobes. Cerci prolonged and upcurved, covered by dense long hairs; inner part membranous, subapically with a stout inner spine; outer surface of cerci sclerotized, outer sclerite kidney-shaped, subapically with a small back-curved spine.
genitalia (Figs 2C-E, 3-4). Dorsal sclerite of epiproct with two elbow-shaped, dark lateral sclerites; inner apex of each lateral sclerite forked; apex of epiproct with a prolonged median sclerite covered by membrane; ventral sclerite with a C-shaped base and two sinuous lateral sclerites, which project forwards and form two apically dentate arms, the arms each with three or four apical teeth. Vesicle of sternum 9 mostly membranous, claviform and slightly constricted basally; hypoproct broad and elliptical, apex extended backwards, with a long triangular sclerite. Paraprocts bilobed; inner lobe weakly sclerotized, finger-shaped with a blunt tip, near half as long as outer lobe; outer lobe strongly sclerotized, broad basally, posteromedial margin forming a long triangular sclerite, inner margin with a projected basal hump covering half of inner lobe. The accidently extruded aedeagus in a paratype cylindrical, mostly membranous, apex with one or two obscure small lobes.

Female
Similar to males in body coloration (Fig. 5A).

Remarks
This species was collected in the afternoon of 5 Oct. 2019, when the adults were emerging massively. The habitat, a very small unnamed stream flows down from a dried mountain (Fig. 7), geographically isolated from other known water systems. An undescribed new genus of Elmidae (Coleoptera) was simultaneously collected in this unique stream, but no mayflies or caddisflies or other aquatic insects were found at that time.

Diagnosis Adult
Cervical gills highly branched.

Male
Paraprocts divided into 3 lobes and with spines or prongs on middle or outer lobes. Cerci membranous, short and unmodified. Dorsal sclerite of epiproct large and broad at base, extending dorsolaterally toward apex, with sclerotized lateral arms, apical portion large and extending laterally over ventral sclerite, bearing small spines or sclerotized scales; ventral sclerite strongly sclerotized, broad at base and tapering toward apex, forming median keel-shaped ridge, apical portion inserted between folds of dorsal sclerite and variously modified, bearing larges spines.

Female
Sternum 7 produced at distal margin, forming a small pregenital plate which covers part of sternum 8. Sternum 8 forming a subgenital plate of variable size but usually small and bifid. Diagnosis Amphinemura jiaoheensis sp. nov. exhibits the typical body color and genitalic characters of genus Amphinemura (Figs 8-11). The new species is apparently distinctive from all congeners by the following combination of characters: 1) male T9 with paired posterior projections which are covered by thick spines; 2) male T10 with two long bunches of stout spines; 3) ventral sclerite of epiproct long, triangular and ventrally fringed with thick spines; 4) median lobe and outer lobe of male paraprocts embracing a membrane, margin of the membrane with long spines; 5) female with a small pregenital plate and a medially divided subgenital plate. The deep posterior notch of tergum 9 together with the long bunches of stout spines on tergum 10 are rarely found in Amphinemura (Figs 9A, 10A). Although a similar notch and spines are also found in Amphinemura leigong Wang & Du, 2006 from Guizhou Province of southwestern China, the structures of the epiproct and paraprocts are entirely different between A. leigong and the new species (Fig. 12).

Etymology
The new species is named after the type locality, Jiaohe City.
abdomen (Figs 8-9, 10A). Abdominal segments generally pale brown; anterior margins of abdominal terga 3-8 each with two dark lateral sclerites; sterna 3-8 each with two dark lateral sclerites. Tergum 9 strongly sclerotized, anterior margin concave, posterior half elevated and with a transverse patch of stout spines. Tergum 10 darkly sclerotized, with a membranous median area, each side of median area with a knob bearing stout spines. Cerci dark brown, coniform and covered by long hairs.  genitalia (9)(10). Dorsal aspect of epiproct covered with spinulose membrane, medially grooved, apex with a pair of small lobes; apical and ventral membrane of epiproct mostly covered with scales. Dorsal sclerite of epiproct with two slender, lateral sclerites projecting to near apex; inside the membrane with a median sclerite; lateral knobs strongly sclerotized, elliptical in dorsal view. Ventral sclerite strongly sclerotized; in lateral view, ventral sclerite constricted basally, mostly forming a subtriangular sclerite fringed with stout spines, apically with more spines. Vesicle of sternum 9 mostly membranous, claviform and slightly constricted basally; hypoproct elongated, apex extended backwards, with a long finger-shaped sclerite. Paraprocts trilobed; inner lobe sclerotized, fusiform with a blunt tip, nearly as long as width of paraprocts; median lobe strongly sclerotized, broad basally, strongly curved dorsad, apex with long spines; outer lobe strongly sclerotized and curved dorsad, sinuous in lateral view; a layer of membrane present between outer lobe and inner lobe, membrane with a caudal patch of long spines and several longer dorsal spines.

Discussion
By describing two new species, the species numbers of Nemoura and Amphinemura from China are updated to 41 and 93, respectively.
Stoneflies of Nemouridae are frequently found and collected in the wild of China, with over 190 species described. However, these small-sized stoneflies have a relatively weak flight ability and are usually   restricted to small habitats, so isolated water habitats usually have different stonefly species. Although Nemoura and Amphinemura are two species-rich genera in China, new taxa of the two genera are continuously discovered and described, suggesting a high biodiversity of Nemouridae in China.