Taxonomic study of the planthopper genus Lacusa Stål, 1862 (Hemiptera, Fulgoromorpha, Lophopidae)

Abstract The planthopper genus Lacusa Stål, 1862 is reviewed. All species are illustrated and male genital characters are provided, and including two new species: L. digitata sp. n. and L. producta sp. n. from Yunnan Province, China. The species L. orientalis Liang, 2000 is removed from this genus based on the frons with median carina and fore femur and tibia flattened but not foliaceous. A key to species is also given. The type specimens of the new species are deposited in the Institute of Entomology, Guizhou University, Guiyang, China (GUGC).

Here, we follow Soulier-Perkins (2001) in treating Sarebasa as a genus distinct from Lacusa based on the morphological characteristics for these two genera (see Table 1). The species Lacusa orientalis Liang, 2000 indicates that the original figures and description are not belong to the genus Lacusa based on the frons with median carina and fore femur and tibia flattened but not foliaceous, and it may be belong to the genera Sarebasa or Acothrura, and its placement is not treated further here. Consequently, this genus now contains only one species: L. fuscofasciata.
In this paper, two new species Lacusa digitata sp. n. and Lacusa producta sp. n. are described and illustrated from Yunnan Province, China. The type specimens of the new species and other materials examined are deposited in the Institute of Entomology, Guizhou University, Guiyang, China (GUGC). The genus Lacusa now contains 3 species, a key is given to separate all species.

Material and methods
Specimens were collected by sweeping net. Dry 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 KEYENCE VHX-1000 system. The genital segments of the examined specimens were macerated in 10% NaOH and drawn from preparations in glycerin jelly using a Leica MZ 12.5 stereomicroscope. Illustrations were scanned with Canon CanoScan LiDE 200 and imported into Adobe Photoshop CS8 for labeling and plate composition. Morphological terminology follows Liang (2000).

Taxonomy
Lacusa Stål http://species-id.net/wiki/Lacusa Stål, 1862: 309;Atkinson 1886: 42;Distant 1906: 323;Muir 1930: 478;Chou et al. 1985: 125;Liang 2000: 283. Type species. Elasmoscelis fuscofasciata Stål, 1854 Description. Body length (from apex of vertex to tip of forewings) less than 10 mm, size medium. Head short, approximately trapezoidal, ratio width of vertex from base to length in middle line 1.6, narrower than pronotum; vertex broader than long, anterior margin straight in dorsal view and not produced anteriorly beyond proximal margin of eyes, lateral margins with carinate, with an obsolete median longitudinal carina. Frons with lateral carinae, and with sublateral carinae fused apically, and without median carina. Rostrum extending to meso-trochanter, with ratio subapical to apical segment 2.0. Pronotum slightly longer than vertex, anterior margin roundly produced, posterior margin approximately straight, tricarinate on disc, lateral areas curved down. Mesonotum broad, with tricarinate on disc. Forewings broadly round at apex, outer and inner margins nearly parallel, precostal area with many oblique transverse parallel crossveins; hindwings narrower than forewings. Legs moderately long, fore femora and tibiae foliaceous. Hind tibiae with 3 lateral spines and 3-4 rows with more than 70 small spines apically, apical spines of first hind tarsal segment separated by a pad of microsetae.
Male genitalia. Pygofer short, upper 1/3 very narrow in lateral view, without appendage. Anal tube longer than pygofer, apex forked in caudal view. Genital styles short to long, dorsolateral with a small hook or a finger-like process near posterior margin. Aedeagus with 2 dorsally directed, spinose processes, dorsally directed at medioventral margin; near base of aedeagus on dorsal side or mediolateral of aedeagus with 2 spinose processes or not; base of aedeagus on dorsal side with 1 spinose process or not, and each base laterally of aedeagus with 1 processes or not.
Diagnosis. The genus Lacusa resembles Pitambara Distant, 1906 andSarebasa Distant, 1909 in having the vertex not produced anteriorly beyond proximal margin of eyes, apical spines of first hind tarsal segment separated by a pad of microsetae, and frontal disc not longitudinally deeply concave, but differs from these genera by the characters noted in Table 1.
Distribution. China, India, Nepal, Burma, Thailand. Note. Chou & Huang (in Chou et al. 1985) described a new species L. yunnanensis from Menglun, Xishuangbanna, Yunnan Province, China, based on one female specimen, and they noted that L. yunnanensis was closely related to L. fuscofasciata, but that it could be distinguished from it by the fuscous transverse band near outer margin on forewing branched and the fuscous meso-and metathorax. Later, Liang (1996) proposed L. yunnanensis as a junior synonym of L. fuscofasciata based on examination of specimens from Yunnan, Guizhou, Guangdong and Hainan Provinces in China.
Body length (from apex of vertex to tip of forewings) of male specimen from Guizhou and Hainan Provinces, relatively small about 6.9 mm, but male specimen from Yunnan Province relatively larger about 8.0 mm. Description. Body length (from apex of vertex to tip of forewings): male 8.5-8.7mm (n=2).
Color pattern of anterior dorsum and face as in Figs 11-15. Pronotum and mesonotum yellowish brown. Tegula yellowish. Ocelli red. Apical margin of forewings maculately piceous. External features as in generic description.
Male genitalia. Pygofer short, upper 1/3 very narrow in lateral view, dorsal margin strongly concave (Fig. 19). Anal tube in dorsal view with ratio length to maximum width 3.0 (Fig. 20). Genital styles long, apex approximately round in lateral view, dorsolateral with a finger-like process near posterior margin (Fig. 19). Aedeagus with 2 dorsally directed, spinose processes, dorsally directed at medioventral margin, and exceed the end of aedeagal shaft; near base of aedeagus on dorsal side of aedeagus with 2 short spinose processes; base of aedeagus on dorsal side with 1 short spinose process (Figs 21,22). Diagnosis. This species is similar to Lacusa fuscofasciata (Stål, 1854) but can be distinguished by the base of aedeagus on dorsal side with one spinose process, near base of aedeagus on dorsal side with two short spinose processes, the anal tube relatively short, and the genital styles much more long.
Etymology. The species name is derived from the Latin word "digitata", indicating that the genital style dorsolateral with a finger-like process near posterior margin.
Color pattern of anterior dorsum and face as in Figs 23-27. General appearance as in Lacusa digitata sp. n., but the body much larger.
Male genitalia. Pygofer short, upper 1/3 very narrow in lateral view, dorsal margin strongly concave, posterior margin angle producted near the middle; (Fig. 28). Anal tube in dorsal view with ratio length to maximum width 4.1 (Fig. 29). Genital styles long, apex approximately round in lateral view, dorsolateral with a small hook process near posterior margin (Fig. 28). Aedeagus with 2 dorsally directed, spinose processes, dorsally directed at medioventral margin, and exceed the end of aedeagal shaft; mediolateral of aedeagus with 2 long spinose processes; base of aedeagus on dorsal side with 1 spinose process (Figs 30, 31). Diagnosis. This species is similar to Lacusa digitata sp. n. but can be distinguished by the mediolateral of aedeagus with two long spinose processes, genital style dorsolaterally with a small hook process near posterior margin, the anal tube relatively long.
Etymology. The species name is derived from the Latin word "producta", indicating that the mediolateral of aedeagus with two long spinose processes.