Revision of the planthopper genus Nycheuma Fennah (Hemiptera, Fulgoromorpha, Delphacidae)

Abstract Chinese species in the genus Nycheuma Fennah, 1964a (Hemiptera: Fulgoromorpha: Delphacidae: Delphacinae: Delphacini) are revised to include three species: Nycheuma cognatum (Muir, 1917), Nycheuma dimorpha (Matsumura, 1910) and Nycheuma nilotica Linnavuori, 1973. Nycheuma coctum Yang, 1989 is placed in synonymy with Nycheuma nilotica Linnavuori, 1973. Nycheuma dimorpha (Matsumura, 1910) is newly recorded from China. The generic characteristics are redefined. The main morphological characters, male genitalia of 3 species are described or redescribed and illustrated. A key to Chinese species in the genus is provided.

Here, the Chinese species of the genus Nycheuma are revised to include three species: N. cognatum (Muir, 1917), N. dimorpha (Matsumura, 1910) and N. nilotica Linnavuori, 1973. N. coctum Yang, 1989 is placed in synonymy with N. nilotica Linnavuori, 1973. N. dimorpha (Matsumura, 1910 collected from Datian National Natural Reserve, Hainan Province, is newly recorded from China. The generic characteristics are redefined. The main morphological characters and male genitalia of 3 species are described or redescribed and illustrated. A key for identifying the Chinese species of Nycheuma is also provided.

Material and methods
The methods and morphological terminology used in this study follow that of Yang and Yang (1986) and Ding (2006). The genital segments of the examined specimens were macerated in 10% KOH and drawn from preparations in glycerin jelly using a light microscope. Illustrations of the specimens were made by using Leica MZ 12.5 stereomicroscope and enhanced using Adobe Photoshop 7.0 (Adobe Systems). Spinal formula means the numbers of apical spines of the hind tibiae and 1 st and 2 nd hind tarsomeres. The type specimens and materials examined are deposited in the Institute of Entomology, Guizhou University, Guiyang, Guizhou Province, China (IEGU). Fennah, 1964Figs 1-36 Nycheuma Fennah, 1964aKuoh et al. 1983: 81;Yang 1989: 95;Ding 2006: 247. Type species. Dicranotropis capensis Muir, 1926, by original designation.
Coloration. General color light yellowish brown to yellowish brown. Pronotum and mesonotum with carinae and border pale yellowish brown. The terminal of first segment and the base of second segment antennae dark brown (Figs 2,14,26). Metapleura with round spot dark brown. Abdomen brown to dark brown. Forewings hyaline, veins dark brown (Figs 3,15,27). Hindwings hyaline with veins dark brown.

Remarks.
In the genera of Delphacini, this genus is most similar to Euidopsis Ribaut, 1948 (with the single species E. truncata Ribaut, 1948), but differs in the following: Frons median carina forked level of ocelli (in Euidopsis, frons median carina forked above level of ocelli); antennae reaching the level of frontoclypeal suture (in Euidopsis, antennae reaching the level of end part of post-clypeus); metatarsal tibial spur with 20 small teeth on lateral margin (in Euidopsis, metatarsal tibial spur with 30 small teeth on lateral margin); pygofer ventral margin with medioventral processes (3 or 1) or absent (in Euidopsis, pygofer ventral margin with 1 small medioventral process); diaphragm without armature (in Euidopsis, diaphragm with 1 armature); aedeagus with 1 long retrose process arising near apex (in Euidopsis, aedeagus with 2 long retrose processes arising near apex). Head and thorax. Vertex (Fig. 1) shorter submedially than wide at base about 1:1.1, Y-shaped carina moderately distinct, basal compartment of vertex wider at base than greatest length about 1.8:1. Frons (Fig. 2) in midline longer than wide at widest part about 2.2:1, widest at level of ocelli. Postclypeus wider at base than frons at apex, slightly wider at base than length in middle line. Rostrum reaching to metatrochanters,  (Figures 1, 2, 4-8); 0.1 mm (Figures 9-12). apical segment distinctly shorter than subapical. Antennae (Fig. 2) surpassing level of middle of postclypeus, basal segment longer than wide about 1.7:1, shorter than second about 1:1.8. Post-tibial spur with about 27 teeth.

Key to known Chinese species of Nycheuma
Male genitalia. Anal segment of male (Figs 4, 5, 8) moderately long, collar-shaped, lateroapical angles very widely separated, each produced caudad and slightly mesad in a stout spinose process. Pygofer in profile (Fig. 5) wider ventrally than dorsally, posterior margin strongly produced caudad medially, in posterior view (Figs 4, 6) with opening small, distinctly wider than long, lateral margin weakly defined, ventral margin shallowly concave, with 3 distinct medioventral processes, middle the longest. Phallus (Figs 8, 9) long, tubular, slightly arched upward medially, reflected cephalad at apex in a flagellum on right side, top of flagellum slightly turned mesad than laterad, pointed at apex, with a large, stout process at middle left and a smaller one near apical fourth right. Orifice terminal dorsad. Suspensorium (Fig. 10) Y-shaped, arms longer than stem. Diaphragm (Fig. 6) rather broad, membranous, triangularly incised dorsally. Opening for genital styles elongate oval. Genital styles (Figs 11, 12) slender, widely divergent, narrowing to apex, inner margin nearly straight, outer margin moderately produced laterad medially.
light yellowish brown to yellowish brown. Forewings (Fig. 15) hyaline, with apex of irregular spot brown. Abdomen with ventral parts dirty yellowish brown.
Head and thorax. Vertex (Fig. 25) wider at base than long submedially about 1.1:1, at apex as wide as at base, basal compartment at base wider than greatest length about 1.8:1. Frons (Fig. 26) in midline longer than wide at widest part about 2.3:1, widest about level of ocelli, lateral carinae nearly straight below ocelli, median carina forked at level of ocelli. Postclypeus (Fig. 26) wider at base than frons at apex, slightly longer than wide at base. Rostrum reaching metacoxae, apical segment shorter than subapical. Antennae (Fig. 26) reaching frontoclypeal suture, basal segment longer than wide about 1.8:1, shorter than second about 1:2.0. Post-tibial spur with about 26 teeth.