Two new species of the tribe Hemisphaeriini (Hemiptera, Fulgoromorpha, Issidae) from southwestern China

Abstract Two new species of the tribe Hemisphaeriini: Ceratogergithusbrachyspinus Yang & Chen, sp. nov. (Yunnan) and Neohemisphaeriusclavatus Yang & Chen, sp. nov. (Guizhou) are described and illustrated. A checklist to Hemisphaeriini genera is provided. The generic characteristics of the genera Ceratogergithus Gnezdilov, 2017 and Neohemisphaerius Chen, Zhang & Chang, 2014 are redefined. Checklists and keys to the species of each genus are given.


Introduction
Hemisphaeriini Melichar, 1906 is the second largest tribe of the planthopper family Issidae with currently 25 genera and 181 species known (Bourgoin 2018). It was erected by Melichar (1906) as family Hemisphaeridae but more recently Gnezdilov (2003Gnezdilov ( , 2013a) downgraded it to the tribe level. Sun et al. (2015) raised the group again to the subfamily level based on partial sequences of the nuclear Wingless (Wg) and 18S rDNA genes and Wang et al. (2016) enlarged the subfamily based on 18S, 28S, COXI and Cytb genes to include four tribes (Kodaianellini, Sarimini, Parahiraciini, Hemisphaeriini). However, here we prefer to follow Gnezdilov (2013a) and treat the group as a tribe of the subfamily Issinae which was also followed by Meng et al (2017).
Hemisphaeriini are characterized as follows: body hemispherical; vertex with anterior margin approximately transverse or triangularly elongate; pronotum with convex anterior margin; forewings thick and convex, claval suture present or absent, venation reticulate; hindwings single-lobed, being either well developed, i.e., longer than half length of forewings, venation reticulate, or rudimentary, shorter than half length of forewings, venation simple.
The tribe Hemisphaeriini is divided into two groups based on the presence or absence of the forewing claval suture. The genera Neohemisphaerius and Paramongoliana both have the forewing claval suture developed. The genus Neohemisphaerius was erected by Chen et al. (2014) for three species (N. wugangensis, N. yangi and N. signifer Walker, 1851) having a forewing with distinct claval suture. Recently  reviewed Neohemisphaerius, transferred species N. signifer Walker, 1851 to Hemisphaerius Schaum, 1850 and described species N. guangxiensis Zhang, Chang & Chen, 2016. The genus Ceratogergithus was erected by Gnezdilov (2017) for three species (C. chelates, C. pseudotessellatus and C. spinosus) having a forewing without a claval suture and pygofer with a large horn-shaped process on posterior margin. In this paper, we describe and illustrate two new species of the tribe Hemisphaeriini, give a checklist to Hemisphaeriini genera, redefine the generic characteristics and provided checklists and keys to the species of these two genera.
Hemisphaeriini are usually collected in broad-leaved forest, although some species are also found on Poaceae in open areas (Gnezdilov 2013b). The species Neohemisphaerius clavatus Yang & Chen, sp. nov. was captured on Bambusa emeiensis.It maybe the second species that feeds exclusively on bamboos (host plant Bambusa emeiensis; Fig. 36), the other species is Rotundiforma nigrimaculata, Meng, Wang & Qin, 2013, whose host plants may be Gigantochloa ligulata Gamble and Dendrocalamus sp. (Meng, Wang & Qin, 2013).

Materials and methods
The morphological terminology follows Chan and Yang (1994) and Bourgoin et al. (2015), except those for male genitalia following Gnezdilov (2003). Dry specimens were observed by stereoscopic microscope Leica M125 for illustration and description. All measurements are in millimeters (mm). The genital segments were separated and macerated in 10% NaOH, transferred to glycerine for observing and drawing. Illustrations of the specimens were made with a Leica MZ 12.5 stereomicroscope. Photographs of the types were taken by KEYENCE VHX-1000C.
Distribution. China: Hainan, Yunnan. Discussion. This genus is similar to Gergithus and Neohemisphaerius, but can be clearly separated from Gergithus by the posterior margin of the pygofer with a large horn-shaped process (Fig. 12) and the aedeagus without pair of short ventral directed toward its apex. It differs from the genus Neohemisphaerius by having a frons without a median carina, with colored marking, a hindwing well developed and longer than half the length of the forewing, and venation reticulate.
Etymology. The name of new species is derived from the Latin words "clavate", referring to the club-shaped process of the aedeagus in basal third (in lateral view).