Three new species of the planthopper genus Sinonissus Wang, Shi & Bourgoin, 2018 from southwest China (Hemiptera, Fulgoromorpha, Issidae)

Abstract The diagnostic characters of the Chinese planthopper genus Sinonissus Wang, Shi & Bourgoin, 2018 are redefined. Three new species of this genus, S. daozhenensis Chang & Chen, sp. nov. (Guizhou), S. hamulatus Chang & Chen, sp. nov. (Guizhou) and S. longicaudus Chang & Chen, sp. nov. (Sichuan) are described and illustrated, and their female genitalia compared. A checklist and key to the Chinese species of Sinonissus are given.

The aim of this paper is to describe three new species of Sinonissus from China bringing the total number of species to four. Generic characteristics are redefined and a checklist and key to Chinese species of Sinonissus is provided.

Materials and methods
The morphological terminology of the head and body follows Chan and Yang (1994) and Bourgoin et al. (2015), and the terminology of male and female genitalia follows Bourgoin (1993) and Gnezdilov (2002. Dry specimens were used for descriptions and illustrations. External morphology was observed under a stereoscopic microscope. All measurements are in millimeters (mm). The body measurements are from the apex of vertex to the tip of the forewings. The genital segments of the examined specimens were macerated in 10% NaOH, washed in water, and transferred to glycerin. Illustrations of the specimens were made with a Leica M125 and Olympus CX41 stereomicroscope. Photographs were taken with a Keyence VHX-1000C.
The type specimens and other examined specimens of the newly described species are all deposited in the Institute of Entomology, Guizhou University, Guiyang, China (IEGU).
Male genitalia. Anal tube (Fig. 19) irregularly pentagonal in dorsal view, the widest in apical 1/3, longer in midline than the width (1.49: 1.00). Anal style (Fig. 19 sturdy and long, located at the base 1/3 of anal tube. Pygofer (Fig. 18) with dorsal margin slightly narrow than ventral margin, posterior margin convex in middle. Genital styles (Fig. 18) relatively rectangular, dorsal margin and ventral margin nearly parallel. Capitulum of genital styles relative long, irregularly triangular, neck obvious (Fig. 20). Phallobase (Figs 21,22) with dorsal lobe cystiform at apical part, with stout rod-like process in apical half in lateral view; lateral lobe splitting into two stout branches; ventral lobe with one lobe-like process near middle in lateral view ( Fig. 21: a), in ventral view, looking like three obvious lobes ( Fig. 22: a), short, the apical margin arced convexly, reaching to 2/3 of dorsal lobe. Aedeagus with long flexuous process at middle in lateral view (Figs 21: b, 22: b).
Etymology. The new species is named for its collecting location in the Daozhen County (Guizhou Province).

Distribution. China (Guizhou).
Remark. This species is similar to S. brunetus, but it differs from the latter by: 1) the width of vertex (Fig. 13) as long as 2.52 times in middle line; 2) phallobase with ventral lobe with lobe-like process near middle in lateral view, in ventral view ventral lobe tree lobes (Figs 21, 22); 3) aedeagus with long flexuous process near middle in lateral view (Fig. 21); 4) female genitalia with posterior connective lamina of gonapophysis IX with median field with symmetrical ear-shaped prominences (Fig. 28).  Diagnosis. This species is similar to S. brunetus, but it differs from the latter by anal tube with spoon-like protrusion in lateral view (Fig. 36) (without spoon-like protrusion in S. brunetus); dorsal lobe of phallobase with rod-like cystiform processes at apical part (Fig. 40) (without rod-like process in S. brunetus); aedeagus with short hooked process, tip of process directed to dorso-posterior (Fig. 40) (tip of process directed to dorso-anterior in S. brunetus).
Male genitalia. Anal tube (Fig. 37) irregularly ligulate in dorsal view, the widest in apical 1/3, longer in midline than the width (1.85: 1.00), in lateral view anal tube with spoon-like protrusion (Fig. 36). Anal style (Fig. 37) sturdy and long, located at the base third of anal tube. Pygofer (Fig. 36) with dorsal margin slightly narrow than ventral margin. Genital styles (Fig. 38) relatively rectangular, dorsal margin slightly arched. Capitulum of genital styles relative long, irregularly triangular, neck obvious (Fig. 39). Phallobase (Figs 40,41) with dorsal lobe finger-like cystiform process near apical part ( Fig. 40:  a), with relatively curved rod-like process in apical 1/3 ( Fig. 40: b) in lateral view; lateral lobe splitting into two stout branches, the apical margin truncated in ventral view; ventral lobe short, unobvious lobe-like process near middle, reaching to 3/4 of dorsal lobe in lateral view, with three unobvious small lobes in ventral view. Aedeagus with short hooked process in the middle in lateral view, directed to dorso-posterior (Figs 40: c,41: c).
Female genitalia . Anal tube (Fig. 45) nearly oval, longer in middle than the widest breadth (1.70: 1.00), the apical margin arched, with unobvious membranous triangular protuberance, the widest at the basal 1/2. Anal style long, located at the basal fifth of anal tube (Fig. 45). Anterior connective lamina of gonapophysis VIII with obviously sclerous triangular process in basal dorsal margin, with three lateral teeth bearing three keels in lateral group and three apical teeth (Fig. 46). Posterior connective lamina of gonapophysis IX (Figs 47, 48) relatively broad, median field symmetrical, with nearly circular prominences, apical margin deeply incised in middle (medial dorsal process) (Fig. 47); ventroposterior lobes bent at obtuse angle (posterior ventral lobes), with membranous triangular process at inner region near the apical part ( Fig. 48). Gonoplacs (Fig. 49) without keels. Hind margin of sternum VII median distinctly concave in ventral view (Fig. 50).
Etymology. This new species is derived from the Latin word hamulatus, referring to the short hamular process of aedeagus.

Distribution. China (Guizhou).
Remarks. This new species is distinguished from other species of this genus by: 1) anal tube irregularly ligulate in dorsal view, with spoon-like protrusion in lateral view (Fig. 37); 2) phallobase with dorsal lobe rod-like cystiform processes at apical part, ventral lobes with three not obvious small lobes in ventral view (Fig. 40); 3) aedeagus with short hooked process in middle in lateral view (Fig. 40); 4) female genitalia with posterior connective lamina of gonapophysis IX in median field with nearly circular process (Fig. 47). Diagnosis. This species is similar to S. brunetus but can be distinguished from the latter by aedeagus (Fig. 59) with long flagellate process in the middle in lateral view; phallobase ( Fig. 60) with ventral lobe triangular, apical margin extremely narrow, the basal part broad in ventral view.
Male genitalia. Anal tube (Fig. 57) irregularly pentagonal in dorsal view, widest in the middle, longer in midline than the width (1.41: 1.00), ventral margin nearly straight. Anal style sturdy and short, located at the base half of anal tube (Fig. 57). Pygofer (Fig. 56) with dorsal margin narrower than ventral margin. Genital styles (Fig. 56) rectangular, dorsal margin and ventral margin nearly parallel. Capitulum of genital styles relatively short, irregularly triangular, neck obvious (Fig. 58). Phallobase (Figs 59, 60) with dorsal lobe small horned cystiform process at apical part ( Fig. 59: a), with relatively straight thin rod-like process in apical 1/4 ( Fig. 59: b) in lateral view; lateral lobe splitting into two stout branches, the apical margin arced in ventral view; ventral lobe short, reaching to 5/6 of dorsal lobe in lateral view, in ventral view the apical part triangular, apical margin extremely narrow, the basal part broad (Figs 59: c,60: c). Aedeagus with long flagellate process in the middle in lateral view, directed to dorso-anterior ( Fig. 59: d).
Etymology. This new species is named for the presence of one long flagellate process of aedeagus.

Distribution. China (Sichuan).
Remarks. This new species is distinguished from other species of this genus by: 1) aedeagus with long flagellate process in the middle in lateral view, directed to dorso-anterior ( Fig. 59: d); 2) phallobase with dorsolateral lobe relatively straight, thin, rod-like process in lateral view ( Fig. 59: b), ventral lobes triangular, apical margin extremely narrow, basal part broad in ventral view (Fig. 60: c); 3) female genitalia with posterior connective lamina of gonapophysis IX median field asymmetrical, with tubercle-like prominences (Fig. 66).

Discussion
According to the geographic distribution of the four species of Sinonissus, all species are distributed in the Oriental region and appear to be found only in China (Fig. 70). Following the taxonomic system of Gnezdilov (2002Gnezdilov ( , 2009Gnezdilov ( , 2013, the family Issidae consists of three tribes: Issini Spinola, 1839, Hemisphaeriini Melichar, 1906, and Parahiraciini Cheng & Yang, 1991 in the subfamily Issinae, and the genera Sinonissus and Celyphoma Emeljanov, 1971 may also be placed in Issini Spinola, 1839, due to the genera having the following characters in common: the small body size, the vertex with its width longer along the midline, the forewing with veins running in parallel, the hind wing reduced or absent, and the phallobase without paired digitate processes on the inner side of the dorsolateral lobe. Wang et al. (2016Wang et al. ( , 2018 placed Sinonissus in the Issini and Celyphoma in Hysteropterini in a new taxonomic system, based on limited molecular data. According to , the subfamily Issinae contains the tribe Issini (including 61 genera) and Hysteropterini (including four genera) in the world. The subfamily Issinae is characteristically distributed in Wallace's Palaearctic region. In China, there are two genera recorded in the tribe Issini, Issus Brullé, 1832, and Sinonissus Wang, Shi & Bourgoin, 2018, and two genera in Hysteropterini: Celyphoma Emeljanov, 1971, Potaninum Gn- ezdilov, 2017. Fewer species were recorded in the subfamily Issinae: Issus coleoptratus (Fabricius, 1781) distributed in Hong Kong and four species of Sinonissus in Sichuan, Chongqing, and Guizhou (see Fig. 70). Gnezdilov (2017) recorded Potaninum boreale (Melichar, 1902) in Sichuan; four species of Celyphoma Emeljanov, 1971 have been recorded in Gansu, Inner Mongolia, Ningxia, Qinghai, and Xingjiang (Meng andWang 2012, Chen et al. 2014). Except Celyphoma, other species and genera of Issinae in China are distributed in the Oriental region. Thus, the phylogeny based on the geographical distribution of Issinae is unstable and paradoxical.
For the female genitalia of Issinae, only female genitalia of Sinonissus and Celyphoma were examined in this work. Sinonissus is obviously different from Celyphoma in the anal tube having an apical margin and an obvious membranous triangular protuberance, widest near the basal half; the anal style is long (Figs 26,45,64) [anal tube with apical margin without triangular protuberance, lateral margin parallel, anal style short in Celyphoma (Figs 71, 73)]; and the anterior connective lamina of gonapophysis VIII has the apical part sclerous (Figs 27,46,65) [membranous in Celyphoma (Figs 72, 74)].
The phylogeny based on a combination of the geographical distribution, male and female characters, and molecular data may be more convincing. Unfortunately, there is no further morphological information and molecular data is unavailable.