Four new species of Agraphydrus Régimbart, 1903 with additional faunastic record from China (Coleoptera, Hydrophilidae, Acidocerinae)

Four new species of Agraphydrus Régimbart are described from China: A. pseudoniger sp. nov. from Shangyou County, Jiangxi Province, A. komareki sp. nov. from Shangchuan island, Taishan County, Guangdong Province, A. sabulosus sp. nov. from Fengkai, Guangdong Province, A. dapengensis sp. nov. from Dapeng peninsula, Shenzhen, Guangdong Province. Diagnosis and illustration of the new species are provided. The key given by Komarek and Hebauer (2018) to Chinese species of Agraphydrus Régimbart is updated.


Introduction
Agraphydrus Régimbart, 1903 contains common water scavenger beetles occurring mainly in the Oriental and Afrotropical Regions (Przewoźny 2017). But it was ignored by hydrophiloid specialists until 10 years ago. By 2013, only 18 species had been described (Short and Fikáček 2013). Hansen (1999a) established the genus Megagraphydrus Hansen, synonymized with Agraphydrus by Minoshima et al. (2015) and all known species transferred to Agraphydrus, and 7 new species from the Oriental region including South China were described. Minoshima (2016) described a new species from Japan and reviewed all known Japanese species. Two species of Chinese Agraphydrus were described by Jia (1998Jia ( , 2010. Komarek and Hebauer (2018) reviewed the Chinese fauna and described 33 new species. The fauna of the Indian subcontinent, Southeast Asia, Afrotropical Region, Western Asia and Australia were reviewed (Komarek 2018(Komarek , 2019(Komarek , 2020Komarek and Freitag 2020). A total of 199 species are now known (Komarek 2020). Most of them occur in the Oriental region including four species that are endemic to Kyushu, Shikoku and adjacent islands, and Ryukyu islands which are considered as part of the Oriental region.

Materials and methods
For this study, we have examined more than 2000 specimens of Chinese Agraphydrus species. Aedeagi of the holotypes of four new species were dissected. After 8-10 hours in 10% KOH at room temperature, dissected 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 after they had been photographed. Habitus photographs were taken using a Nikon DS-Ri2 mounted on a Nikon SMZ25; layers were captured and aligned in the NIS-Elements software. Photographs of genitalia were taken using a Zeiss AxioCam HRc mounted on a Zeiss AX10 microscope with the Axio Vision SE64 software. These images were systematic punctures distinct; ground punctures on frons as on clypeus, systematic puncture distinct. Eyes large, not protruding. Antennae (Fig. 3B) with eight antennomeres. Maxillary palp (Fig. 3C) about as long as pronotum in midline, 0.75-0.84× as long as maximum width of clypeus; length ratio palpomere 4:3 =1.27-1.31, palpomere 4 asymmetrical. Mentum (Fig. 3D) with several fine punctures on lateral portions, without microsculpture.
Thorax. Pronotum ca. 2× as wide as long, pronotal ground punctures as on frons, surface between ground punctures without microsculpture, systematic punctures distinct, forming a row in the anterolateral and located lateral middle position of the clypeus, each with a long seta. Elytral ground punctation as on head and pronotum, surface between ground punctures as on pronotum; with four distinct rows of systematic punctures, mesal rows of systematic punctures reaching anterior margin. Prosternum slightly convex, without carina medially, with a transverse groove. Mesoventrite (Fig. 3E) with moderate bulge, abruptly declining posteriorly, with horizontal ridge posteriorly. Metaventrite with distinct mesal convexity, bearing a small glabrous area posteromedial part.
Legs. Pubescence present on proximal 2/3 of profemora ( Fig. 3G) with oblique hairline, on about half of mesofemora ( Fig. 3H) with straight hairline, restricted to a narrow anterior strip on the basal half of metafemora (Fig. 3I).
Aedeagus (Fig. 7A). Length: 0.53mm. Phallobase about 2/3× as long as the parameres, manubrium wide at base, about third of the width of phallobase, apex handle shape. Parameres wide at the base, margin narrowing apicad; apex obliquely, with cuspidal, hook-like subapical protrusion and with strong constriction in the apical 1/4; middle margin slight sigmoid-shape. Basal protrusion extending into 1/5 of the phallobase. Median lobe wide at the base, strongly narrowing toward apex; apex dentiform, almost as long as the parameres, corona moderately large, located in middle position; basal apophyses long, vertical, barb shape, almost reaching half of phallobase.
Etymology. This species is named after the type locality, Dapeng Peninsula, Shenzhen, Guangdong Province.
Distribution. Only known from type locality. Remark. This species shares similar dorsal coloration, maxillary palpi unicolorous yellow, mesoventrite with strong mesal bulge and similar aedeagus with A. activus Komarek & Hebauer and A. anhuianus Hebauer, but differs from them by its clypeus without small median notch, antennae with eight antennomeres, pubescence restricted to a narrow anterior strip on the basal half of metafemora, phallobase moderately long and the lateral margin of parameres slightly curved (phallobase short in A. activus and A. anhuianus, the lateral margin of parameres straight in proximal 3/4 in A. activus and lateral margin slightly sinuate in proximal 3/4 in A. anhuianus). It shares maxillary palpi unicolorous yellow, mesoventrite with distinct mesal bulge and metafemoral pubescence restricted to anterior margin or absent with A. longipalpus (Jia) and A. calvus Komarek & Hebauer, but differs from them by parameres with hook-like subapical protrusion and median lobe with corona located in middle position (parameres without hook-like subapical protrusion, median lobe with corona located in basal position, crescentic sclerotized structure existing in A. longipalpus; parameres without hook-like subapical protrusion, median lobe with corona situated in distal to midlength, shield-shaped sclerotized structure existing in A. calvus). Diagnosis. This species is distinguished from the other species of Agraphydrus by the following combination of characters: Labrum, clypeus and frons black; preocular patches present; clypeus entirely microsculptured; maxillary palpi with apical palpomere about 1.5-1.6× as long as penultimate, palpomere 4 without apical infuscation; antennae with eight antennomeres; elytra with four systematic punctures; meso-and metafemora pubescent in about basal 3/4; aedeagus with median lobe wider than parameres, corona large, located at basal third; parameres with indistinct subapical constriction. Differs from A. gracilipalpis by eight antennomeres and features of the aedeagus.
Thorax. Pronotum ca. 1.1-1.3× as wide as long, pronotal ground punctures as on frons, surface between ground punctures with shallow microsculpture; systematic punctures indistinct, only several coarse punctures existing on the middle of the lateral part. Elytral ground punctation slightly larger than that on head and pronotum, interspaces 1.4-1.6× as large as punctures, surface between ground punctures as on the pronotum; 4 rows of systematic punctures distinct, with strongly reduced number of punctures, mesal row not reaching anterior margin, intervals without coarse punctures. Prosternum slightly convex, without carina medially. Mesoventrite ( Fig. 4E) with distinct, flexuose and narrow mesal carina. Metaventrite distinctly convex mesally, with a small glabrous area posteromedially.
Etymology. This species is named after Dr. Albrecht Komarek, a specialist in Hydrophilidae, who works at Naturhistorisches Museum, Wien, Austria.
Distribution. Only known type locality.
Remark. This species belongs to the group of species entirely chagrinate clypeus and unicolorous maxillary palpomere 4, together with A. igneus Komarek & Hebauer, A.umbrosus Komarek & Hebauer , A. gracilipalpis Komarek & Hebauer and A. schoenmanni Komarek & Hebauer. It differs from A. igneus by eight antennomeres (nine antennomeres in A. igneus), pronotum without anterolateral chagrination, lateral margin of parameres straight and parameres slightly constricted subapically (lateral margin of parameres strongly sigmoid and with distinct subapical constriction in A. igneus), from A.umbrosus by eight antennomeres (nine antennomeres in A.umbrosus) and parameres moderately narrow, lateral margin straight with indistinct subapical constriction (Parameres moderately wide; lateral margins very slightly curved with distinct subapical constriction in A.umbrosus), from A. gracilipalpis by eight antennomeres and lateral margin of parameres with indistinct subapical constriction and median lobe with apical third gradually narrowing apicad (lateral margin of parameres with distinct supapical constriction and median lobe with margins of ventral face converging to narrow, parallel-sided apical half in A. gracilipalpis), from A. schoenmanni by eight antennomeres (nine antennomeres in A. schoenmanni), lateral margin of parameres straight with indistinct subapical constriction and median lobe with corona locating at the basal third (lateral margins of aedeagus distinctly sigmoid with strong subapical constriction and median lobe with corona located at apical third in A. schoenmanni). Very similar to A. reticuliceps, differs in its small size, entire chagrinate clypeus, eight antennomeres (nine antennomeres in A. reticuliceps), median lobe with apical third gradually narrowing apicad and bluntly rounded apically (median lobe apex globular, with subapical constriction in A. reticuliceps). Diagnosis. This species is distinguished from other species of Agraphydrus by the following combination of characters: labrum, clypeus and frons black; without preocular patches; maxillary palpi with apical palpomere slightly longer than penultimate, palpomere 4 without apical infuscation; clypeus without microsculpture, antennae with eight antennomeres; elytra with four rows of systematic punctures; meso-and metafemora pubescent in about basal 2/3; aedeagus with apex of the parameres distinct bending mesally, corona large, located at subapical position.
Thorax. Pronotum ca. 1.10-1.25× as wide as long, pronotal ground punctures sparse, as on frons, interspaces 1-3× as large as punctures, surface between ground punctures with microsculpture, systematic punctures distinct, located in the anterior and lateral middle position of the clypeus, each with a long seta on the middle. Elytral ground puncture slightly larger than that on head and pronotum, interspaces 1-2× as large as punctures, surface between ground punctures as on the pronotum; with four distinct rows of systematic punctures, mesal rows reaching anterior margin. Prosternum slightly convex, without median carina. Mesoventrite ( Fig. 5F) with narrow, needle-like and strong median carina, extending to middle of mesofemora. Metaventrite moderately convex mesally, with small glabrous area posteromedially.
Etymology. Specific name derived from Latin "pseudo", false, and "niger", black, refers to the similarity with Agraphydrus niger Komarek & Hebauer, 2018. Distribution. CHINA (Jiangxi, Guangdong       from A. politus by small size, with four rows of punctures (ten in A. politus), phallobase about as long as parameres and apex of parameres moderately curved inwards (phallobase slightly longer than the parameres, parameres strongly curved inwards subapically in A. politus); from A. fasciatus by clypeus without preocular patches, pronotum and elytra black and parameres slightly longer than median lobe (parameres about 2x as wide as median lobe in A. fasciatus); from A. niger by clypeus with a deep excision anteriorly and small median notch and mesal rows of systematic punctures reaching anterior margin. Diagnosis. This species is distinguished from the other species of Agraphydrus by the following combination of characters: labrum, clypeus and frons black; preocular spots present; clypeus entirely microsculptured; maxillary palpi with apical palpomere about 1.5× as long as the penultimate one, palpomere 4 without apical infuscation; antennae with 9 antennomeres; elytra with four irregular series of coarse punctures; meso-and metafemora pubescent in about basal 2/3; aedeagus with median lobe narrowing toward the apex; parameres with obvious subapical constriction.
Thorax. Pronotum ca. 3-4× as wide as long, pronotal ground punctures as on frons and clypeus, surface between ground punctures smooth, without microsculpture; systematic punctures distinct, located at the middle of the lateral margin. Elytral ground punctures as that on head and pronotum; systematic punctures distinct, arranged into 4 rows, mesal row not reaching anterior margin, intervals without coarse punctures. Prosternum weakly convex, not carinate medially, with a transverse groove. Mesoventrite (Fig. 6E) slightly bulged. Metaventrite with a bulge mesally, hydrofuge pubescence present on the surface, only absent from a small area on posteromedian part.
Etymology. This species is named after the holotype acquisition environment, which has a lot of sand.
Distribution. China (Guangdong, Jiangxi  . flavonotus), apex of median lobe delicate and basal apophyses reaching the 1/3 of the phallobase (apex of median lobe flatly and the basal apophyses reaching half of phallobase in A. flavonotus). Differs from A. arduus and A. igneus by pronotum without anterolateral chagrination, parameres with apex obtuse, moderately flat, lateral margin of the parameres slightly curved and median lobe narrowing toward apex (parameres with apex delicate, bulgy, lateral margin of parameres slightly sigmoid and median lobe with blunt or flat, rarely slightly indented apex in A. arduus, and apex of parameres strongly inflated, lateral margin of the parameres strongly sigmoid and apex of median lobe bluntly rounded with numerous distinct setae on top in A. igneus).

Discussion
For a long time Agraphydrus was a group of scavenger beetles, ignored by entomologists, that is, until recently. The study by Minoshima (2015Minoshima ( , 2016, Komarek (2018Komarek ( , 2019 and Komarek and Hebauer (2018) shows that it is a very species-rich genus and many new species can be expected. The vast majority of the individuals were collected south of the Chang Jiang, Asia's longest river, dividing China into its northern and southern part. Only two species, A. jilanzhui Komarek & Hebauer and A. audax Komarek & Hebauer, are distributed northward over the Chang Jiang to Gansu and Shaanxi, respectively. No representative is hitherto found in other Provinces north of the Huanghe River.
The Japanese fauna is usually considered as Palearctic by entomologists (e.g., Hansen 199b). However, there is no doubt that Ryukyu islands are part of the Oriental region (Jia and Tang 2018). Lots of data on insects show that the fauna of Kyushu, Shikoku and adjacent islands, is very similar to those of Taiwan of China and the Philippines (Hansen 1999b;Short and Fikáček 2011;Przewoźny 2017), but clearly different form other Palearctic regions including north Honshu and Hokkaido in Japan. So, Kyushu, Shikoku and adjacent islands should be considered as part of the Oriental region.
Based on known data, the Chinese fauna of Agraphydrus is more similar to the fauna of Southeast Asia than to the fauna of the Indian Subcontinent. Of 42 known species from China, only four species are known in both China and the Indian Subcontinent. A. pauculus (Knisch, 1924) and A. pygmaeus (Knisch, 1924) (Hansen), are also distributed in Southeast Asia. Obviously, the Chinese fauna of Agraphydrus has a closer relationship to Southeast Asia than to the Indian Subcontinent. (Komarek and Hebauer 2018;Komarek 2018Komarek , 2019. their help in collecting and photographing the specimens. We also thank Albrecht Komarek, an Austrian specialist of Hydrophilidae, and Robert Angus, who is a specialist on aquatic beetles, in UK, for their reviewing, and also improving the manuscript for English. This study was supported by GDAS Special Project of Science and Technology Development (2020GDSYL-20200102021, 2020GDASYL-20200301003) and by Shenzhen Wilde life Conservation Division.