A new species of Laccobius Erichson, 1837 (Hydrophilidae, Coleoptera) from the Chinese Himalaya, with comments on taxonomic status of subgenera Glyptolaccobius Gentili, 1989 and Cyclolaccobius Gentili, 1991 and additional faunistic records from China

Abstract A new species of the water scavenger beetle, Laccobius (Glyptolaccobius) motuoensissp. nov., is described from Motuo County, Xizang, China and its diagnostic characters are illustrated. Examination of this new species and re-examination of previously described species revealed that the separation of the subgenus Glyptolaccobius Gentili, 1989 and Cyclolaccobius Gentili, 1991 is artificial: both subgenera are hence combined here. Cyclolaccobiussyn. nov. is synonymized with Glyptolaccobius, and the latter is shown to be diagnosed by 7-segmented antennae as a unique synapomorphy. All species treated until now under Cyclolaccobius are here transferred to Glyptolaccobius, with the only exception of L. hingstoni Orchymont, 1926, L. jumlanus Gentili, 2015 and L. zugmayeri Knisch, 1910 which are tentatively transferred to the subgenus Hydroxenus Wollaston, 1867, as their antennae bear eight antennomeres. Three species are recorded for the first time from China: L. (Microlaccobius) orientalis Knisch, 1924 from Xizang, Laccobius (M.) exilis Gentili,1974 from Xinjiang, and Laccobius (M.) sublaevis J. Sahlberg, 1900 from Xinjiang. Additional faunistic data from China are provided for the following species: L. (Microlaccobius) hammondi Gentili, 1984, Laccobius (M.) formosus Gentili, 1979, Laccobius (Hydroxenus) hingstoni d’Orchymont, 1926, Laccobius (Glyptolaccobius) yunnanensis Gentili, 2003, Laccobius (Compsolaccobius) decorus (Gyllenhal, 1827), Laccobius (Dimorpholaccobius) bipunctatus (Fabricius, 1775), Laccobius (D.) striatulus (Fabricius, 1775), Laccobius (s. str.) bedeli Sharp, 1884, L. (s. str.) binotatus d’Orchymont, 1934, Laccobius (s. str.) cinereus Motschulsky, 1860, and Laccobius (s. str.) minutus (Linnaeus, 1758).


Introduction
Since the species of the genus Laccobius Erichson, 1837 occurring in China and neighboring areas were reviewed by Gentili (1995Gentili ( , 2003 and Jia et al. (2013a), and only three species of this genus were described from this region more recently (Jia et al. 2013b;Gentili 2015;Zhang and Jia 2017). The fauna of the eastern Himalayas and neighboring mountain systems have not yet been investigated properly and the discovery of additional species is expected.
In total, 34 species of Laccobius have been recorded from China to date (Hansen 1999;Short and Fikáček 2011;Fikáček et al. 2015;Zhang and Jia 2017). Here, we summarize new findings based on the material collected in Xinjiang, Qinghai, Xizang and northwestern Sichuan during 2016-2018 deposited in the collection of Sun Yatsen University, Guangzhou, China. A new species is described and three species are reported from China for the first time. Additional faunistic records are provided for several other species. The total number of Laccobius species occurring in China now rises to 38. The examination of the new species also urged us to re-examine the antennal morphology of the species assigned to the subgenera Glyptolaccobius Gentili, 1989 and Cyclolaccobius Gentili, 1991; this is revealed to be unique for these two subgenera indicating that they should be combined here into a single subgenus.

Material and methods
A few specimens were dissected for each species examined. After 8-10 hours in 10% KOH at room temperature, male genitalia were transferred to a drop of distilled water, remaining membranes were removed under a compound microscope, and the cleaned genitalia was subsequently mounted into a drop of glycerin on a piece of transparent plastic attached below the respective specimen. Habitus photographs were taken using a Zeiss Discovery V20 with Zeiss AxioCam HRc. Photographs of genitalia were taken using Zeiss Axioskop 40 binocular microscope with a QIM-AGING Micropublisher 3.3 RTV camera; the pictures were subsequently combined with the Auto-Montage software. Scanning electron microscope photographs were taken using a Phenom Pro SEM.
Thorax. Pronotum transverse, smooth; black with greenish reflection, lateral margins with yellow stripe that extends to posterior margin near posterior corner (Figs 1, 2), the yellow patch with posterior margin 2× as wide as anterior margin; punctures coarse and sparse, bearing decumbent yellowish setae; lateral stria fine, ending in posterior corner, but shortly continuous along anterior margin. Scutellar shield equilaterally triangular, black with few punctures. Prosternum black with dense decumbent pubescence, with a longitudinal keel medially (Fig. 10). Mesoventrite with arrow-head-shaped elevation ( Fig. 10), the top of the elevation with a tuft of long setae; a longitudinal carina reaching to posterior margin of mesocoxae (Fig. 10). Metaventrite pubescent with a very narrow longitudinal glabrous area medioposteriorly (Fig. 10). Elytra smooth, slightly elongate, ca. 1.1× as long as wide, dark brown with wide lateral yellow margin that always narrower than posterior margin of pronotal lateral yellow margin (Figs 1, 4); posterior half yellow, fused with lateral yellow margin (Figs 1, 2); base of elytra with a pair of distinct pale yellow spots ca. at mid width (Figs 1, 3), sometimes elytra almost black on disc, and the basal yellow spot absent or unclear (Fig. 4); primary series punctures not sulciform; primary series of punctures strong and coarse, regularly arranged; secondary ones with small and scarce punctures (Fig. 11). Epipleura oblique, ending at level of metafemora.
Aedeagus. (Figs 5,6). Total length 0.42 mm. parameres nearly 1.6× as long as phallobase. Phallobase 1.3× as long as wide. Median lobe as long as parameres, broad basally, gradually narrowed from base to mid length and then slightly widened to apex; with a series of backward directed setae subapically, apex rounded. Parameres subrectangular apically, almost as wide as medial lobe apically. Differential diagnosis. This species closely resembles L. yunnanensis Gentili, 2003 and L. sipeki Gentili & Fikáček, 2009 in the genital morphology (including the series of long hairs on distal half of the median lobe) and the coloration of elytra having a dark base with small basal spots and widely pale apical portion. It can be distinguished from L. yunnanensis by having an elytral series regular throughout (somewhat irregular  at base in L. yunnanensis), primary series of punctures distinctly stronger and coarser than secondary ones (with some punctures at least as large as those on primary series in L. yunnanensis) and the median lobe ca. the same width in apical half (distinctly widened apically in L. yunnanensis). It can be distinguished from L. sipeki by the absence of the parasutural furrow (with distinct rather deep parasutural groove in L. sipeki) and the apex of the median lobe reaching the level of parameral apices only (slightly overlapping parameral apices in L. sipeki).
Etymology. This species is named after type locality. Distribution. Only known from two close localities in the eastern Himalaya (Xizang, Motuo County).

Synonymy of the subgenera Glyptolaccobius and Cyclolaccobius
The subgenera Glyptolaccobius and Cyclolaccobius both contain species that inhabit mostly hygropetric habitats (seepages, wet rocks, sides of waterfalls) and are both characterized by large transverse eyes, which distinguish them from remaining groups of the genus Laccobius. The principal character distinguishing both subgenera is the presence (in Glyptolaccobius) or absence (in Cyclolaccobius) of the 'parasutural furrow', i.e., the longitudinal impression situated parallel to the suture in the posterior half of elytra. This character is usually clearly visible in Glyptolaccobius and clearly absent in Cyclolaccobius, but confusion still happens: Gentili (2006) and Gentili and Fikáček (2009) described three species of Glyptolaccobius (L. silvester Gentili, 2006, L. hanka Gentili & Fikáček, 2009and L. josefi Gentili & Fikáček, 2009) which were later transferred to Cyclolaccobius by Gentili (2012). Both subgenera were mentioned as bearing 8-segmented antenna, similarly to all other Laccobius species (see Gentili 2006, fig. 3).
Recently, Zhang and Jia (2017) described a new Glyptolaccobius species from Yunnan, China (L. yinziweii Zhang & Jia, 2017) which is unusual among all known Laccobius as its antenna consisted of seven antennomeres only: scape, pedicel, one intermediate antennomere (instead of two in other Laccobius species), cupule and three-segmented antennal club (see Zhang and Jia 2017: figs 8, 9) showing scanning electron micrographs of the antennae). The examination of the antennal morphology of L. motuoensis described in this paper surprisingly revealed the same morphology with only seven antennomeres. In contrast to L. yinziweii, L. motuoensis clearly lacks the parasutural furrow, and both species sharing the unique antennal morphology are hence members of different subgenera. Moreover, the genital morphology of L. motuoensis closely resembles that of L. yunnanensis (a member of Cyclolaccobius) and L. sipeki (member of Glyptolaccobius). In addition, the elytral coloration of L. motuoensis, with pale spots basally, completely dark portion subbasally and at mid length and a pale portion in the apical third to fourth of the elytra, is found in a group of species of which some are treated as Glyptolaccobius (L. sipeki, L. yinziweii) and some as Cyclolaccobius (L. josefi, L. hanka and L. nigrogilvus).
All these observations motivated us to check the antennal morphology of a wider spectrum of species assigned to Glyptolaccobius and Cyclolaccobius. We examined the following species: L. affinis Knisch, 1927 (the type species of Glyptolaccobius), L. pluvialis Gentili, 2006, L. qinlingensis Jia, Gentili & Fikáček, 2013, L. sipeki Gentili & Fikáček, 2009, L. yinziweii Zhang & Jia, 2017 (all latter with the parasutural furrow, i.e., members of Glyptolaccobius), L. hanka Gentili & Fikáček, 2009, L. hainanensis Jia, Gentili & Fikáček, 2013, L. hingstoni Orchymont, 1926, L. martini Jia, Song & Gentili, 2013, L. nitidus Gentili, 1984, L. politus Gentili, 1979, and L. yunnanensis Gentili, 2003 (all latter without parasutural furrow, i.e., members of Cyclolaccobius). All of these except L. hingstoni have 7-segmented antennae. Moreover, L. hanka (without parasutural furrow, member of Cyclolaccobius) and L. pluvialis (with parasutural furrow, member of Glyptolaccobius) were found as closely related sister taxa in the molecular phylogeny of Toussaint and Short (2018). All this evidence clearly indicates that species assigned at the moment to the subgenera Glyptolaccobius and Cyclolaccobius likely form a monophyletic group characterized by a unique synapomorphy within Laccobius, i.e., the 7-segmented antenna. The presence/absence of the parasutural furrow seems to be a phylogenetically flexible character within Laccobius since species that closely resemble each other in other characters sometimes differ in the presence/absence of the parasutural furrow only. We hence conclude that keeping Glyptolaccobius and Cyclolaccobius as two subgenera is actually more confusing than helpful for taxonomic work, even if these subgenera would be considered just as artificial groups designed to facilitate taxonomic work on this large genus (until a phylogenetic study is performed). For this reason, we are performing the following taxonomic changes here: 1. We synonymize Glyptolaccobius Gentili, 1989with Cyclolaccobius Gentili, 1991 syn. nov. 2. Glyptolaccobius sensu nov. is diagnosed by having antennae with seven antennomeres (in contrast to eight antennomeres in remaining subgenera of Laccobius). All species currently treated under Cyclolaccobius and having 7-segmented antennae are here transferred to Glyptolaccobius. 3. The only three species treated until now as Cyclolaccobius which do not have 7-segmented antennae (i.e., L. hingstoni, L. zugmayeri Knisch, 1910 andL. yumlanus Gentili, 2015;see Gentili 2015) are tentatively transferred to the subgenus Hydroxenus Wollaston, 1867 (= Platylaccobius Gentili, 1974) where they were assigned originally before being transferred to Cyclolaccobius. These three species differ from other Cyclolaccobius and Glyptolaccobius species by having a much larger body size, elongate oval body, eyes not so transversely reniform and by their biology: L. hingstoni was collected in the littoral zone of standing waters (ponds, lakes) i.e. not in hygropetric habitats or habitats associated with stony streams which are typical for the Glyptolaccobius+Cyclolaccobius species.
Additional studies are necessary to understand the systematics of Laccobius and to test the phylogenetic position of L. zugmayeri and related species as well as to test the monophyly of the subgenera. At the moment, only the subgenus Glyptolaccobius in the new meaning (i.e., containing all Laccobius species with 7-segmented antenna, and characterized by a hygropetric lifestyle) and Yateberosus (a New Caledonia endemic subgenus with the larva having closed spiracular system and abdomen bearing tracheal gills, see Fikáček et al. 2018) seem to be supported by unique morphological synapomorphies combined with geographically limited range (in Yateberosus) or a specific lifestyle (in Glyptolaccobius), and hence are candidates for monophyletic groups. The monophyly of all other subgenera is doubtful and needs to be further tested.

Key to species of Laccobius (Glyptolaccobius) from China
Gentili (1995) provided a series of keys for the identification of all Laccobius species known from China and neighboring areas. These keys are still up-to-date for most subgenera and include even the species recorded subsequently as new for China (Jia et al. 2013; this paper, see below). Only two parts need to be updated: (1) Laccobius jumlanus Gentili, 2015 was mistakenly treated under the name L. zugmayeri Knisch, 1910 in the key (see Gentili 2015 for details); and (2) the key of species of the subgenus Glyptolaccobius sensu nov. needs to be updated as all species described as new since 1995 belong to this subgenus. The following key to Glyptolaccobius sensu nov. in China is modified from Gentili (1996Gentili ( , 1998. Body length 2.0-2.8 mm; elytral borders and epipleura are swollen at base; median lobe narrowly pointed apically (Gentili 1995: figs 52, 53 Median lobe strongly constricted subapically (Jia et al. 2013: figs10-12 Diagnosis. Body length 2.8-3.0 mm. Frons between eyes ca. 2.6-3.0× as wide as one eye in dorsal view. Pronotum black or dark brown medially, with a pair of light spots at anterior margin, with broad yellow band laterally, without shagreen, smooth and shining. Punctures of third and fifth elytral rows uniform, arranged almost in a straight line (a few punctures slightly out of line). Aedeagus (Fig. 27): Basal two-thirds of parameres almost parallel-sided, gradually narrowed towards apex in apical onethird, pointed apically; median lobe almost as wide as parameres basally, gradually narrowed towards apex, rounded apically.
Distribution. Widely distributed species, recorded from north Africa through Near East and Central Asia to the Himalaya and Tibetan Plateau (Hansen 1999 Diagnosis. Body length 2.3-2.7 mm. Frons between eyes ca. 2.8-3.0× as wide as one eye in dorsal view. Pronotum black or dark brown medially, without a pair of light spots at anterior margin, with broad yellow band laterally, without shagreen, smooth and shining. Punctures of third and fifth elytral rows uniform, arranged almost in a straight line (Gentili 1995: fig. 162). Aedeagus (Fig. 26) with parameres narrowed towards apex, rounded apically; median lobe wide throughout, slightly wider than parameres, especially in apical part.
Distribution. Widely distributed species, recorded from Turkey through Central Asia to the Himalaya, Myanmar and the Tibetan Plateau (Gentili 1995, Hansen 1999. New for China. Diagnosis. Size 2.8-3.0 mm. Frons between eyes ca. 2.8-3.0× as wide as one eye. Pronotum black or dark brown medially, without a pair of light spots at anterior margin, with broad yellow band laterally, without shagreen, smooth and shining. Punctures of third and fifth elytral rows in disorder, not arranged in straight lines (Gentili 1995: fig. 161). Aedeagus (Fig. 28) with median lobe slightly widened apically; parameres with subparallel sides, rounded apically.

Laccobius
Distribution. Central Asian species reaching to the Tibetan Plateau and the Himalaya Region (Gentili 1995. New for China. Distribution. See Fikáček et al. (2015). New for Qinghai-Tibetan Plateau.