Taxonomic study of the genus Malaxa Melichar, with descriptions of two new species from China (Hemiptera, Fulgoroidea, Delphacidae)

Abstract Two new species of the delphacid genusMalaxa Melichar, 1914, M.hamuliferumsp. nov. and M.tricuspissp. nov., are described and illustrated from southwest China (Yunnan and Hainan), providing the genus with eleven species in total. A key is provided to distinguish the seven Chinese species in the genus.

Species of Malaxa from China with reported plant associations feed on bamboo. Specimens have been collected on leaves of bamboo in several genera, including Bambusa, Indocalamus, Fargesia and Phyllostachys Chen et al. 2006;Hou et al. 2013).
Herein, two new species: Malaxa hamuliferum sp. nov. and M. tricuspis sp. nov. are described and illustrated from Hainan and Yunnan province, China. A key to species of Malaxa from China is provided.

Materials and methods
The morphological terminology and measurements follow Hou et al. (2013). Body length was measured from apex of vertex to tip of tegmina. Dry male specimens were used for the description and illustration. External morphology was observed under a stereoscopic microscope and characters were measured with an ocular micrometer. Color pictures for adult habitus were obtained by the KEYENCE VHX-1000 system. The genital segments of the examined specimens were macerated in 10% KOH and drawn from preparations in glycerin jelly using a Leica MZ 12.5 stereomicroscope. Illustrations were scanned with a Canon CanoScan LiDE 200 and imported into Adobe Photoshop 6.0 for labeling and plate composition.
The type specimens of the new species are deposited in the Institute of Entomology, Guizhou University, Guiyang, China (IEGU).

Key to species (males) of Malaxa from China (revised from Hou et al. 2013)
1 Postclypeus yellow; tegmina with apical veins Cu 1 and M 3 diverging apically, posterior half of apical tegmina dark brown (see Chen et al. 2006 Etymology. The specific name is derived from the Latin word "hamulus" and the postfix "-ferus", referring to the middle of genital styles with large process, hook-like. Measurements. Body length including tegmina: male 3.9-4.1 mm (N = 10); female 4.8-5.0 mm (N = 5); tegmen length: male 3.4-3.6 mm (N = 10); female 4.0-4.4 mm (N = 5).  Diagnosis. The salient features of the new species include the following: aedeagus with phallobase broad basally, apical third narrowing abruptly, and genital styles with large process at middle, hook-like.
Description. Coloration. General color pale yellowish brown, with dark brown to black markings, shiny (Figs 1, 2). Vertex with basal half yellowish brown, apical half pale black. Pronotum and mesonotum brown to black except each lateral side yellow (Figs 5, 6). Frons and genae black. Clypeus with basal half black, rest yellow. Rostrum yellow except apex pale brown (Fig. 7). Eyes and ocelli reddish brown. First segment of antennae with dorsal side pale yellow, with ventral side brown, second segment dark brown. Tegmina with basal half yellow except areas around apex of Cu 1 , after bifurcation of IA and IIA hyaline, at apical half, along Sc 1 , sc-r and area between R 1 and M 2 dark brown (Fig. 8). Wings hyaline, veins brown. Abdomen with dorsal side black, with ventral side yellow white. Genitalia dark brown.

Distribution. Southwest China (Yunnan).
Remarks. This species is similar to Malaxa semifusca  but differs from it by: (1) frons and genae black, clypeus with basal half black (frons with apical third, genae with ventral half and clypeus yellow in M. semifusca); (2) anal segment of male without process (anal segment with left lateroapical process small and obtuse in M. semifusca); (3) aedeagus with phallobase without tooth at apex (aedeagus with phallobase incomplete, apex membraneous, with several teeth along margin and around apex in M. semifusca). Etymology. The specific name is derived from the Latin word "tricuspis", referring to aedeagus with three small processes.
Diagnosis. The salient features of the new species include the following: left lateroapical process of anal segment stout and twisted, tapering apically; aedeagus with three small processes.
Description. Coloration. General color pale yellowish brown, with dark brown to black markings, shiny (Figs 3, 4). Vertex, pronotum and mesonotum pale black except each lateral side yellow (Figs 15, 16). Frons and genae black except small area at apex yellow. Clypeus with basal half black, rest yellow (Fig. 17). Eyes and ocelli reddish brown. Antennae with dorsal side pale yellow, with ventral side brown. Tegmina with basal half pale yellow except areas around Sc+R, apex of Cu 1 , after bifurcation of IA and IIA hyaline, at apical half, along Sc 1 , sc-r, and area between R 1 and M 2 dark brown (Fig. 18). Wings hyaline, veins brown. Abdomen with dorsal side black, with ventral side yellow. Genitalia brown.
Male genitalia. Anal segment of male small, ring like, left lateroapical process stout and twisted, tapering to apex (Fig. 19). Pygofer in profile tapering to dorsad, ventral angles strongly produced (Fig. 20), in posterior view with opening longer than wide (Fig. 19), in ventral view medioventral processes wide, concave medially (Fig. 21). Aedeagus simple, tubular, broad basally then tapering to apex, with stout process at base, a spine at basal third and with small tooth at apical third (Figs 22,23). Genital styles long, broad basally, apical half narrowing abruptly, inner margin with several teeth at middle (Figs 19, 24).

Distribution. Southwest China (Hainan).
Remarks. This species is similar to Malaxa fusca  but differs from it by: (1) anal segment of male with left lateroapical process twisted but not Slike, not swelled subapically (anal segment with left lateroapical process twisted, S-like, swelled subapically in M. fusca); (2) aedeagus with stout process at base, a spine at basal third and with small tooth at apical third (aedeagus with small process at base and with a spine near middle in M. fusca); (3) genital styles with apical half narrowing abruptly, not forked at apex (genital styles with outer angle forked at apex, inner branch longer than outer one in M. fusca). This species is also similar to M. delicata Ding & Yang, 1986 but differs from it by: (1) anal segment of male with left lateroapical process twisted near base (anal segment with left lateroapical process twisted near apex in M. delicata) (2) aedeagus with stout process at base, a spine at basal third and with small tooth at apical third (aedeagus with process at base and with small spine at basal third in M. delicata); (3) genital styles with outer angle not forked at apex (genital styles with outer angle forked at apex, two branches subequally long in M. delicata). Melichar (1914) established the genus Malaxa with the type species M. acutipennis Melichar, 1914 from Philippines. This genus is only known to occur in the Oriental region, with highest species density occurring in China. Bartlett and Kennedy (2018: 515-516) noted "Several differences can be observed between Malaxa acutipennis and the Chinese species in that genus. The most salient of these are that M. acutipennis has an apically pointed forewing (rounded in all other Malaxa) with the leading margin arced (giving the wing a spatulate appearance; parallel-sided in all other Malaxa); the more elongate pronotum with the carinae clearly reaching the hind margin (most other Malaxa with a relatively shorter pronotum with lateral carinae not reaching); and the genitalia with a simple ventral margin of the pygofer opening (vs. having projections on the opening of the pygofer); and the simple anal tube (most Chinese Malaxa bear a single, large, asymmetrical projection on the anal tube)."

Discussion
The Malaxa species distributed in China with common type characters: body slender and elongate, often with blackish brown markings; antennae cylindrical, very long, surpassing apex of clypeus, basal segment shorter than the second segment (0.40-0.56: 1); tegmina apically rounded, leading margin straight; anal tube of male either simple or with 1-2 processes; opening of pygofer usually bearing two broad lamellate medioventral processes, between them a V-like emargination; genital styles broad in basal half, forked or with process at apex; aedeagus with or without phallobase, phallus tubular, curved Clike and directed segmental venter. Based mainly on the characters of the morphological and male genitalia, we also found obvious differences between the Chinese Malaxa and the type species M. acutipennis, which agrees Bartlett and Kennedy's (2018) description. Therefore, the genus level composition of Malaxa may require reconsideration, with the general concern that the Chinese species may not be congeneric with the type species from the Philippines. However, M. obtusipennis Muir, 1919 (from Malaysia: Sabah) was described from three females. The features of the male terminalia of M. obtusipennis are not available for consideration, which limits our ability to place this species. Therefore, in this paper, we provisionally place the two new species in the genus Malaxa, but the genus level composition of Malaxa is required to reconsideration and more taxon samples or molecular data are still required to confirm the relationships within Malaxa in the future.