Taxonomic review of the planthopper genus Orthopagus (Hemiptera, Fulgoromorpha, Dictyopharidae), with descriptions of two new species

The Oriental and eastern Palaearctic planthopper genusOrthopagusUhler, 1897 (Hemiptera, Fulgoromorpha, Dictyopharidae, Dictyopharinae, Orthopagini) is revised. Six species are included:O.bartlettiSong, Malenovský & Deckert,sp. n.(described from India),O.exoletus(Melichar, 1903),comb. n.,stat. rev.(material studied from India and Sri Lanka),O.hainanensisSong, Chen & Liang,sp. n.(described from China: Hainan island),O.lunuliferUhler, 1897 (the type species of the genus; confirmed from Japan, China, Vietnam, Laos, India, and Nepal),O.philippinusMelichar, 1914 (Philippines), andO.splendens(Germar, 1830) (confirmed from China, Vietnam, Thailand, India, Malaysia, and Indonesia).OrthopagusheliosMelichar, 1912 is newly synonymized withO.lunulifer. Lectotypes are designated forO.helios, O.heliosvar.diffusus Melichar, 1912,O.elegansMelichar, 1912, andO.philippinus.DictyopharaindianaWalker, 1851 is considered a nomen dubium. All species are redescribed, including habitus photographs and detailed illustrations of the male genitalia. Female genitalia are described for the genus for the first time. A key for identification of the species ofOrthopagusand a distribution map are given.


Introduction
The family Dictyopharidae is one of twenty currently recognized extant families of planthoppers (Hemiptera, Fulgoromorpha) (Bourgoin 2018). With more than 720 species in 155 extant and extinct genera, this family is currently divided into two subfamilies Dictyopharinae Spinola, 1839 and Orgeriinae Fieber, 1872 (Muir 1923, Metcalf 1946, Song et al. 2016c, 2018. The dictyopharid species are widely distributed in all biogeographic regions, being most numerous in tropical and subtropical zones, e.g. in South America, the Oriental region and the East Indies (Metcalf 1946, Bourgoin 2018. Both adults One of them is Orthopagini first recognized by Emeljanov (1983) based on the type genus Orthopagus Uhler, 1897 and six other genera, and later extended to include a total of 23 genera (Emeljanov 2011, Song et al. 2014, 2016d. The Orthopagini taxa are mainly distributed in the Old World tropics and subtropics, including sub-Saharan Africa, India, Sri Lanka, southern China, Indochina, Malaya, the Greater Sunda Islands, the Philippines, the Moluccas, and northern Australia (Song et al. 2016d, Bourgoin 2018. A few species of Orthopagus and Saigona Matsumura, 1910 extend into the eastern Palaearctic region (Liang and Song 2006). Recently, most Orthopagini genera have been revised (Liang and Song 2006, Song and Liang 2006a, b, 2007, 2011, 2012a, b, Song et al. 2012, 2014, 2016a, b, d, 2017. The monophyly of the tribe was tested and phylogenetic relationships among most genera were analysed by Song et al. (2014Song et al. ( , 2016dSong et al. ( , 2018. Morphological characters support Orthopagini as a sister-group to Dictyopharini (Song et al. 2016b(Song et al. , d, 2018. The genus Orthopagus has been known to include five valid species distributed in the Oriental and eastern Palaearctic regions (Bourgoin 2018). Its complicated nomenclatorial and taxonomic history can be summarised as follows. The type species, Orthopagus lunulifer Uhler, 1897 was described from Japan. Orthopagus is congeneric with Anagnia erected earlier by Stål (1861) for Flata splendens Germar, 1830 from Java, which Stål considered a senior synonym of Dictyophara indiana Walker, 1851 described from India, but Anagnia had been preoccupied by Walker (1854) for a genus of moths in the Erebidae (Lepidoptera). Melichar (1903) described Udugama based on Udugama exoleta Melichar, 1903 from Sri Lanka. Kirkaldy (1904) proposed a new generic name Kareol Kirkaldy to replace Anagnia Stål (nec Walker). Kareol was later synonymized with Udugama by Distant (1906), and the latter was synonymized with Orthopagus by Oshanin (1908). Distant (1906) also proposed that the species names U. exoleta and F. splendens were synonyms. Melichar (1912) redescribed Orthopagus and added two species names based on specimens from Taiwan, China, O. elegans Melichar, 1912 andO. helios Melichar, 1912. Udugama fletcheri Kirkaldy, 1908 also listed by Melichar (1912) in Orthopagus is currently considered a junior synonym of Truncatomeria viridistigma (Kirby, 1891) (see Song and Liang 2011). The last species described so far and still placed in Orthopagus was O. philippinus Melichar, 1914 from Luzon, the Philippines (Melichar 1914).
Based on examination of most Orthopagus types and a critical review of the literature, Orthopagus is here revised. We redescribe all previously known taxa and add two new species, O. bartletti Song, Malenovský & Deckert, sp. n. from India and O. hainanensis Song, Chen & Liang, sp. n. from China. We provide an identification key and photographic illustrations for each species, showing also the structures of the male and female genitalia, described and illustrated in detail.

Material and methods
The specimens studied in the course of this work are deposited in the following institutions, which are subsequently referred to by their acronyms: The post-abdomina of the specimens used for dissections were cleared in 10% KOH at room temperature for ca. 6-12 hours, rinsed and examined in distilled H 2 O and then transferred to 10% glycerol and enclosed in microvials to be preserved with the specimens. Observations were conducted under a stereomicroscope, measurements and photography under Zeiss Discovery V12 or Leica M205 C stereomicroscopes equipped with a Nikon D7000 digital camera in IZCAS. Some final images were compiled from multiple photographs using CombineZM image stacking software and improved with the Adobe Photoshop CS5 software.
The morphological terminology and measurements used in this study follow Song et al. (2016cSong et al. ( , d, 2018 for most characters, Bourgoin (1993) for the female genitalia, and Bourgoin et al. (2015) for the forewing.
terior margin of eyes, median carina sharp and complete; frons with intermediate carinae approaching frontoclypeal suture, median carina complete; pronotum with intermediate carinae distinct in basal half; mesonotum with lateral carinae curving anteriad towards median carina; forewings with a wide sublunate streak on distal half of wing, transverse veins sparse, pterostigmal area with 2-4 cells; fore femora flattened and dilated, with a large and blunt spine near apex; hind tibiae with seven apical teeth; phallobase with inflated membranous paired lobes, with or without numerous small superficial spines.

Description.
Adult. General colour of body brownish ochraceous to dark brown marbled, with pale green and reddish ochraceous streaks on dorsum (Figs 1A-B, 2A-L). Females distinctly darker than males. Head pale ochraceous with dark brown markings on vertex and frons the extent of which varies among species. Clypeus pale ochraceous basally, with two small dark spots at frontoclypeal suture on each side of median carina, apical half dark brown. Pronotum brownish ochraceous to dark brown, median carina and spots on lateral marginal areas and paranotal lobes pale ochraceous. Mesonotum dark brown, median and lateral carinae, and lateral marginal areas flavescent or greenish. Forewing veins light ochraceous, membrane hyaline to translucent with three dark brown markings: (i) a large sublunate streak extending along the posterio-apical margin from basal portion of areola postica across apical portions of cells of the medial area to the apex of RP vein; (ii) triangular patch on pterostigma, extending also into radial area (C1 cell) and rarely more mesiad as a dark streak along nodal line; (iii) streak along postclaval wing margin filling out whole inner claval cell (Figs 2A-L, 3A-F). Hind wing veins ochraceous, membrane clear, with a more or less developed dark brown marking along the apical portion of CuA 1 vein. Legs pale to dark brown: femora dull ochraceous to fuscous, banded and marked with ivory white; fore and mid tibiae yellowish green to ochraceous with two dark brown transverse bands medially; hind tibiae yellowish green (pale ochraceous in old dry-mounted specimens), with base and apex including lateral and apical spines fuscous; fore and mid tarsi fuscous, hind tarsi ochraceous. Abdomen dorsally and ventrally ochraceous to dark brown, with dark brown or pale ochraceous spots and stripes of various sizes and shape.
Female genitalia. Gonocoxae VIII ( Fig. 7D) with two membranous and flattened endogonocoxal processes (Gxp) on endogonocoxal lobe: Gxp1 large and elongate, with a long sclerotized plate in it; Gxp2 smaller and shorter. Gonapophyses VIII (  belonging to Orthopagus could not be sufficiently cleared during this study: Dictyophora [sic] indiana Walker, 1851: 310 described from India (without more precise locality data). This name was synonymized under Anagnia splendens (Germar) (now Orthopagus splendens) by Stål (1861): 149. However, this synonymy is considered doubtful here because the original description of D. indiana lacks diagnostic information and illustrations which would enable recognition of its species identity and the single available type specimen of D. indiana (deposited in BMNH) could not be directly examined during this study due to its very poor condition which did not allow its sending out for a loan. Based on a photograph kindly provided by M. D. Webb (BMNH), the type specimen belongs to an Orthopagus species but it lacks the abdomen and its head has been partly damaged. As the details of the male genitalia and the coloration and proportions of the head, i.e. the characters which are missing or damaged in the type, are the most reliable diagnostic morphological characters of Orthopagus species, it is not certain that even a direct examination of the type would help to solve the identity of D. indiana. Therefore, it is proposed here to treat Dictyophara indiana as a nomen dubium. Currently, four Orthopagus species are known from the Indian subcontinent: O. bartletti sp. n., O. exoletus, O. lunulifer and O. splendens, of which O. exoletus is the most widespread (Fig. 11). plate extended cephalad into genital cavity, forming wall of gonospiculum. Gonoplacs ( Fig. 7G) with two lobes homologous; lateral lobe large and moderately sclerotized, with long setae at apex; the posterior lobe membranous, containing long sclerotized plate. Segment X (Fig. 7A) large and broad in dorsal view, apex deeply excavated to accommodate anal style; anal style large and elongate. Female ectodermal genital ducts ditrysian. Bursa copulatrix ( Fig. 7A-C) superficially membranous, regularly gridded, without sclerotized ornamentations. A pair of large digitiform glands (Fig. 7B) branched at anterior extremity of the anterior vagina on each side of the spermatheca. Spermatheca (Fig. 7B) divided clearly into five parts: orificium receptaculi, ductus receptaculi, diverticulum ductus, pars intermedialis, and glandula apicalis.
Fifth instar nymph. See Yang and Yeh (1994) for a detailed description.

Diversity and distribution.
Orthopagus is revised here to include six valid species (see below). The species of the genus are widely distributed in the Oriental and eastern Palaearctic regions from India in the southwest to Japan in the northeast (Fig. 11). Diagnosis. Orthopagus bartletti sp. n. can be separated from all other Orthopagus species by the very short head, hardly produced in front of eyes; the forewings with a brownish streak along nodal line connecting the pterostigmal area with the distal sublunate streak; the dorso-posterior margin of the male pygofer with a large and broad process forming two distinct angles; the robust male segment X; and the lobes of the phallobase muricate apically.

Nomenclatorial remark on
Description. Measurements (1 male). Body length (from apex of head to tip of forewings): 11.5 mm; head length (from apex of cephalic process to base of eyes): 1.2 mm; head width (including eyes): 1.5 mm; forewing length: 9.6 mm. Coloration ( Fig. 2A-B). General colour brownish ochraceous marked with dark brown on dorsum. Head greenish ochraceous, vertex with basal corners, a pair of round patches in basal third, and apical diamond-shaped spot dark brown (Fig. 4A); frons with median area between intermediate carinae extensively dark brown anteriorly and with series of small pale fuscous spots along intermediate and lateral carinae and narrow ivory white band basally (Fig. 4C). Clypeus ivory white, with two small spots at base and apex dark brown. Compound eyes fuscous with posterior margin ochraceous; ocelli purplish-red. Pronotum brownish ochraceous, median carina, apical marginal areas of ventral lobes, and posterior lateral angles ivory white. Mesonotum brownish ochraceous (Fig. 4A). Forewings hyaline, veins ochraceous, pterostigmal area, a streak along nodal line, and a wide sublunate streak on distal third dull ochraceous; posterior (claval) margin broadly faintly brown (Fig. 3A). Hind wings hyaline, veins and an apical spot dull ochraceous. Legs pale brown; fore femora subapically and hind tibiae at base and apex (including lateral and apical spines) blackish. Abdomen dorsally and ventrally brownish ochraceous.
Female genitalia unknown.
Etymology. The new species is named after Dr. Charles R. Bartlett, collector of the type specimen and curator of the insect collection at the Department of Entomology and Wildlife Ecology, University of Delaware, USA, in recognition of his kindest help and support to the first author when he visited UDCC in 2017. The species name is to be treated as a noun in genitive case.
Distribution. So far only known from southwestern India (Fig. 11).
Coloration. General coloration as in generic description ( Fig. 2A). Vertex predominantly light ochraceous, with 3-4 pairs of small dark brown markings: an elongate patch on each side of midline apically, a small spot at each lateral keel medially, a roundish spot on each side of midline at basal third, and a small spot in each postero-lateral corner (Fig. 5A). Frons light ochraceous with small dark brown spots along intermediate and lateral carinae, frons base slightly infuscated (Fig. 5C). Forewing membrane pattern as in Fig. 3B. Hind wing membrane with a relatively narrow dark brown streak along the apical portion of CuA 1 vein, extending along hind wing apical margin in some specimens.
Structure. Head with cephalic process very short, not inflated (Figs 5A-C). Vertex (Fig. 5A) with ratio of length at midline to width between eyes 1.2-1.5. Transition of vertex to frons narrowly rounded in lateral view (Fig. 5B). Frons relatively broad, with ratio of length at midline to maximum width 2.3-2.7.
Male genitalia. Pygofer, in lateral view, with dorso-posterior margin produced into a relatively large but narrow, tooth-like, apically obtuse process (Fig. 5E); in ventral view ( Fig. 5F) much longer than in dorsal view ( Fig. 5D) with ratio of ventral to dorsal width about 2.6. Gonostyles (Fig. 5E) large and broad medially, with dorsal margin weakly sinuate medially. Aedeagus ( Fig. 5G-I) relatively small and slender, endosomal processes curved laterad and slightly ventro-or dorsoanteriad, membranous, without distinct minute superficial spines; phallobase with three pairs of relatively small (not conspicuously inflated) membranous lobes: a pair of elongate lateral lobes with their apices gradually convergent and tapering posteriad ( Fig. 5H-I), a pair of elongate thumb-like ventral lobes, directed ventroposteriad (Fig. 5H), and a pair of small thumb-like dorsal lobes, directed dorsolaterad (Fig. 5G). Segment X, in lateral view, elongate, basal half narrow, gradually widening to apex beyond middle (Fig. 5E); in dorsal view, widest medially, with ratio of length to maximum width 1.1 (Fig. 5D).
Female genitalia as in generic description.
Distribution. India (southwestern part and West Bengal), Sri Lanka (Fig. 11). bels handwritten by Melichar as "Udugama" and "exoleta det. Melichar" and a dark red label "Typus" originally also attached to the specimen by Melichar, it probably cannot be considered as a syntype because it differs in its locality and deposition from the information published in the original description and probably it was also collected later than the original species description had been published. Melichar did not use type labels in the modern sense. He had rather adopted the practice of placing a ʻtypeʼ label on one or more specimens of the most taxa (even on species previously described by other authors and identified by Melichar), specimens presumably which he himself used for comparison (Young andSoós 1964, Wilson andMalenovský 2007).  (Melichar 1903). Distant (1906) synonymized this species name with Udugama splendens described from Java, Indonesia. However, Kirkaldy (1908), probably based on comparisons of figures in Melichar (1903) and Distant (1906), commented that U. exoleta was "very different" from U. splendens in having a much longer face. Nevertheless, the synonymy of U. exoleta with U. splendens was accepted by Melichar (1912), and later included in Metcalf's (1946) catalogue of world Dictyopharidae.

Orthopagus hainanensis
Based on our critical review of the published information and examination of Orthopagus material from Sri Lanka which agrees with the original description of U. exoleta, we propose here to resurrect Orthopagus exoletus comb. n. from the synonymy with O. splendens and to restore it as a valid species. Orthopagus exoletus can be distinguished from O. splendens by the coloration of the vertex and the structure of the male genitalia, particularly the structure of the endosomal processes of aedeagus, lobes of the phallobase and the shape of the segment X. The relative length of frons mentioned by Kirkaldy (1908) is probably not a relevant diagnostic character because the length of the head in Orthopagus species varies within a certain range.
According to Melichar (1903), U. exoleta was described based on five female specimens from "Moruwale", deposited in the collection of the museum in Colombo, Sri Lanka. This material was not available to our study. Nevertheless, we have studied one female from Sri Lanka, "Puttalam" preserved in Melichar's personal collection in MMBC. Even though this specimen bears original identification la- CAS); 1 male, Mangrin, 9.vi.1904;1 female, Mon Boi, 29.v.1904 (both BMNH).

Diagnosis.
Orthopagus hainanensis sp. n. is similar to O. lunulifer in most characters, but can be differentiated from the latter by the ivory white to pale ochraceous vertex with a pair of dark brown spots on each side of midline in basal third (in O. lunulifer, the vertex is nearly dark brown from base to apex) and the male segment X being elongate in dorsal view, with ratio of length to width near middle 1.9-2.0 (in O. lunulifer, the male segment X is shorter and wider in dorsal view, with ratio of length to width near middle 1.2-1.3). Orthopagus hainanensis sp. n. is also similar to O. exoletus in the predominantly light vertex but it differs from the latter by a slightly longer head, the male pygofer with dorso-posterior margin produced into a broad and short lobe in lateral view (the pygofer bears a larger tooth-like process dorso-posteriorly in O. exoletus) and the aedeagus with two pairs of larger (more strongly inflated) dorsolateral membranous lobes and endosomal processes covered with minute spines (indistinct in O. exoletus).
Coloration. General coloration as in generic description ( Fig. 2E-F). Head ivory white to pale ochraceous, vertex with basal corners castaneous, a pair of large fuscous patches on each side of midline at basal third, and pale fuscous apical diamond-shaped spot (Fig. 6A); frons pale with series of small pale fuscous spots along intermediate and lateral carinae, base without distinct dark spot (Fig. 6C). Forewing pattern as in Fig. 3C. Hind wing membrane with a relatively narrow dark brown streak along the apical portion of CuA 1 vein, extending along hind wing apical margin.
Female genitalia as in generic description (Fig. 7A-G).

Orthopagus lunulifer
Coloration. General coloration as in generic description (Figs 1A, 2G-H). Vertex dark brown with five light ochraceous streaks: along median carina in anterior third (in some specimens, the whole median carina is light), along each lateral carina subapically and along each lateral carina basally, the latter streaks being sickle-shaped and curved to median carina at the base (Fig. 8A). Frons light ochraceous with small dark brown spots along intermediate and lateral carinae, frons base slightly infuscated (Fig. 8C). Forewing membrane pattern as in Fig. 3D. Hind wing membrane with a dark brown streak along the apical portion of CuA 1 vein, extending along hind wing apical margin.
Structure. Head with cephalic process moderately long, not inflated (Figs 8A-C). Vertex (Fig. 8A) with ratio of length at midline to width between eyes 1.6-2.0. Transition of vertex to frons relatively sharp, almost angular in lateral view (Fig. 8B). Frons relatively narrow, with ratio of length at midline to maximum width 2.6-3.0.
Male genitalia. Pygofer, in lateral view (Fig. 8E), with dorso-posterior margin produced into a short and broad lobe; in ventral view (Fig. 8F) much longer than in dorsal view (Fig. 8D) with ratio of ventral to dorsal length about 4.0. Gonostyles (Fig. 8E-F) large, broad medially, with dorsal margin weakly sinuate. Aedeagus (Fig.  8G-I) with endosomal processes extended posteriad and strongly curved dorso-anteriad, relatively short, their apices not reaching the base of phallobase; phallobase with one pair of large, strongly inflated dorsolateral lobes (Fig.  8H), their apices blunt, and one pair of small, thumb-like ventral lobes, directed posteriad (Fig. 8I). Segment X, in lateral view, narrow basally, widening to apex beyond middle, apex subacute (Fig. 8E); in dorsal view, relatively short and broad in dorsal view, widest medially, with ratio of length to maximum width 1.2-1.3 (Fig. 8D).
Female genitalia as in generic description.

Distribution.
Widely distributed in tropical, subtropical and temperate eastern Asia (Japan, China, Korea, Vietnam, Laos, northeastern India and Nepal).
Ecology and economic importance. Adult O. lunulifer was reported as a minor pest of leaves of Morus alba L. (Pu and Mao 2012) and Camellia oleifera Abel in southeastern China (Zhao et al. 2013). Matsumura (1910) listed "Anagnia splendens" among pests of sugarcane in Taiwan; this record perhaps also refers to O. lunulifer.

Remarks.
Erroneously according to Metcalf (1946), Matsumura (1905a, b) considered O. lunulifer to be a junior synonym of Anagnia splendens (Germar). As he probably studied material from Japan, the description and illustration of "Anagnia splendens" in Matsumura (1905a) probably refer to O. lunulifer (i.e., the only Orthopagus species currently confirmed from Japan). The same is probable for the records and a figure of "Anagnia splendens" from Okinawa and Taiwan published in Matsumura (1905b and1910, respectively). Melichar (1912) differentiated O. elegans, O. helios and O. lunulifer based on slight differences in the transparency of the forewing membrane, extent of the dark brown apical band on the forewing and the shape of frons. Based on a study of material from Taiwan, Schumacher (1915) suggested that Orthopagus helios and O. elegans described by Melichar (1912) (Metcalf 1946). We have examined the corresponding type specimens and additional specimens from the same series collected by H. Sauter in Taiwan and currently deposited in HNHM, MFNB, MMBC, SDEI, and SNSD, and confirm here Schumacher's conclusion. Simultaneously, we suggest that O. helios should be treated as a junior synonym of O. lunulifer because we consider the differences among these taxa listed by Melichar (1912) ICZN (1999). Liang (1996) designated the lectotype for O. lunulifer, and provided a left lateral view of male genitalia for this species. Detailed illustrations of the male and female genitalia (but no detailed description) were also provided for O. lunulifer by Song et al. (2016dSong et al. ( , 2018. The single male specimen examined from Nepal (Chitwan National Park) is identical in external characters to specimens of O. lunulifer from Japan, China, Taiwan and Vietnam. However, it differs in the shape of the lobe on the dorso-posterior margin of the pygofer which is smaller (shorter and simply angular) than in the rest of O. lunulifer males studied. The phallobase of this specimen could not be sufficiently compared as its membranous lobes failed to inflate during the preparation. More specimens and data are needed to confirm the identification.
Coloration. General coloration as in generic description (Figs 2I-J). Vertex predominantly dark brown, lateral margins with a pale ochraceous S-shaped streak in posterior three quarters (Fig. 9A). Frons light ochraceous with small dark brown spots along intermediate and lateral carinae and a large roundish dark brown spot at base (Fig. 9C). Forewing membrane pattern as in Fig. 3E. Hind wing membrane with a narrow dark brown infuscation along the apical portion of CuA 1 vein, not extending along hind wing apical margin.
Structure. Head with cephalic process moderately elongate (Figs 9A-B). Vertex (Fig. 9A) with ratio of length at midline to width between eyes 1.6-1.8. Transition of vertex to frons blunt, broadly rounded in lateral view, cephalic process thus appearing inflated and bulbous apically (Fig. 9B). Frons relatively narrow, with ratio of length at midline to maximum width 2.7-3.1.
Male genitalia. Pygofer, in lateral view, with dorso-posterior margin produced into a relatively large but narrow, tooth-like, apically obtuse process (Fig. 9E); in ventral view ( Fig. 9F) much longer than in dorsal view ( Fig. 9D) with ratio of ventral to dorsal width about 2.5. Gonostyles (Fig.  9G) large, broad medially, with dorsal margin weakly sinuate. Aedeagus (Fig. 9H-J) with endosomal processes covered with minute superficial spines, extended posteriad and strongly curved laterad and dorso-anteriad but not reaching the base of phallobase; phallobase with one pair of large, strongly inflated dorsolateral lobes, their apex convergent and tapering posteriad (Fig. 9I), and one pair of smaller, thumb-like ventral lobes, directed ventro-posteriad ( Fig.  9I-J). Segment X, in lateral view, relatively narrow basally, widening to apex beyond middle, apex blunt (Fig. 9E); in dorsal view, relatively large and broad, widest in apical third, ratio of length to maximum width 1.0-1.1 (Fig. 9D).
Female genitalia as in generic description.
Distribution. So far only known from the Luzon island, Philippines.

Remarks.
Orthopagus philippinus can be easily recognized from other species of the genus by the shape of the head and the presence of a relatively large roundish dark spot at base of frons which is present in all specimens studied. Melichar (1914) indicated that he described this species based on five (male and female) specimens from "Luzon, Los Baños, Mt. Maquiling (C. F. Baker)". Six specimens (1 male, 5 females) preserved in Melichar personal collection in MMBC and labelled as either from Los Baños or Mt. Makiling and collected by Baker are considered here as the original syntypes. The male specimen is designated here as the lectotype for O. philippinus to stabilize the nomenclature according to Article 74 of ICZN (1999).  Bierman, 1907: 161;Bierman (1908): 151, Pl.
Female genitalia as in generic description.
Remarks. Flata splendens was described by Germar (1830) from Java, and was designated as the type species of Anagnia by Stål (1861). Udugama flavocarinata Bierman, 1907 from Java was considered as a junior synonym of O. splendens by Melichar (1912). Orthopagus splendens var. tibialis Kirkaldy was differentiated from the typical form by having "the fore and middle tibiae distinctly bi-or tri-angulate with brownish" (Kirkaldy and Muir 1913). However, this pattern is typical for all Orthopagus species.
Orthopagus splendens has been frequently confused in literature and museum collections with other species of the genus. It can be differentiated from them by the combination of the following characters: a relatively small body size, a moderately short head, an extensive dark pattern on vertex, the pygofer with dorso-posterior margin bearing a relatively large but narrow, simply tooth-like process, the endosomal processes of the aedeagus relatively long and robust, covered with minute superficial spines and phallotheca bearing two pairs of membranous lobes.

Discussion and conclusions
The six currently recognised species of Orthopagus are very similar in external morphology and female genitalia and also the differences in the male genitalia between some pairs of species are subtle. This is probably the reason for the relatively complicated synonymy and frequent misidentifications by previous authors. The individual species can be recognised mainly by the differences in extent of the dark pattern on the vertex and frons, the size and shape of the cephalic process, the extent of the dark brown infuscation on the hind wing, the shape of the male pygofer, the structure of the aedeagus (the length of the endosomal processes and the shape and size of the membranous lobes of the phallobase), and the shape of the male segment X.
Three species, Orthopagus bartletti sp. n., O. hainanensis sp. n., and O. philippinus, have, as far as known, very restricted distributions, being endemic to south-western India and the islands of Hainan (China) and Luzon (Philippines), respectively. The distribution of O. exoletus is, as far as known, restricted to the Indian subcontinent (southern India, West Bengal and Sri Lanka). Orthopagus lunulifer is widespread in the tropical, subtropical and temperate eastern Asia from Nepal and northeastern India in the southwest to Korea and Japan in the northeast, while the distribution of O. splendens is probably restricted to the tropical zone slightly more south. The areas of distribution of the latter two species, however, overlap in northeastern India (Assam), northern Vietnam, and southern China (Yunnan, Hainan and Taiwan) (Fig. 11). Orthopagus splendens is also sympatric with O. hainanensis in the Hainan island, and O. exoletus is sympatric with O. bartletti in southwestern India. More data, e.g. from molecular markers, are needed to infer a phylogeny of Orthopagus and propose some evolutionary scenario which would also help to explain these distributions and mechanisms of speciation involved. More studies are also needed to understand the ecology and economic importance of Orthopagus species since the currently available data are scarce and insufficient (Matsumura 1910, Pu and Mao 2012, Zhao et al. 2013). According to the phylogenetic hypothesis by Song et al. (2016dSong et al. ( , 2018, Orthopagus is most closely related to the monotypic genus Dictyomeria Song, Webb & Liang, 2016, represented by D. simulata (Distant, 1906) from India which has been known only from the female holotype so far (Song et al. 2016d). Both genera share a similar forewing shape, venation and dark brown pattern on the forewing membrane. Orthopagus can be distinguished from Dictyomeria by the following characters: short and nearly straight head (in contrast, the cephalic process in Dictyomeria is strongly upturned in front of eyes); frons with median carina ridged and intermediate carinae approaching frontoclypeal suture (with median carina robust and strongly convex and intermediate carinae extending to anterior margin of eyes in Dictyomeria); pronotum with intermediate carinae distinct in basal half (indistinct in Dictyomeria); fore femora flattened and dilated, with a large and blunt spine near apex (fore femora not flattened and dilated, with a small spine in Dictyomeria).
Orthopagus is also similar, e.g. in the head morphology, to another monotypic genus Truncatomeria Song & Liang, 2011, established for T. viridistigma (Kirby, 1891) (= Udugama fletcheri Kirkaldy, 1908) from Sri Lanka. Orthopagus can be distinguished from Truncatomeria by the following characters: frons with median carina mod-erately ridged (very strongly produced in Truncatomeria); fore femora flattened and dilated, with a large blunt spine near apex (slender with a short small spine near apex in Truncatomeria); the hind tibiae with seven blacktipped apical spines (eight spines in Truncatomeria); the forewing relatively shorter, broader and with membrane bearing well-developed dark brown markings (clear in Truncatomeria); and the long, apically pointed endosomal processes of the aedeagus (short and apically obtuse in Truncatomeria; see Song and Liang 2011). The similarity in the head shape between the two genera might be a symplesiomorphy or a convergence; according to Song et al. (2016dSong et al. ( , 2018, Truncatomeria is more closely related to Centromeria Stål, 1870 and a few other genera. Froeschner and Thomas J. Henry (USNM). Charles Bartlett, Jacek Szwedo and Chandrashekara Viraktamath are greatly appreciated for their efforts in improving this paper as reviewers. We also wish to thank Dr Martin Husemann for his editorial help.
The work on which this paper is based was supported by the grants from the National Natural Science Foundation of China (no. 31572297, to Z.S.S.) and Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (no. Y4ZK111B01), and partially by the grants from the National Natural Science Foundation of China (nos. 31561163003 and 31572298, to A.P.L.).