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GENUS HYDROPHILUS GEOFFROY, 1762 (FIG. 6A–C, M) Material examined: Hydrophilus piceus: 2 spec. (BMNH): Greece, Corfu, R. Angus lgt. Hydrophilus pistaceus Castelnau, 1840: 1 spec. (BMNH): Spain, Caceres, Abadia, R. Angus lgt. Karyotype: 2 n = 28 + Xy p (♂). The chromosomes are short. C-banding shows all the autosomes with heavy centromeric C-bands accounting for most of their length. Comments on karyotypes: Mitosis and meiosis were studied in four species of Hydrophilus [Hydrophilus acuminatus Motschulsky, 1853, Hydrophilus indicus (Bedel, 1891), Hydrophilus piceus and Hydrophilus triangularis Say, 1823] by previous authors (Arnold, 1909; Asana et al., 1942; Smith, 1953; Agarawal, 1960a), all revealing the karyotype 2 n = 28 + Xy p (♂), which is in agreement with our findings., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134, {"references":["Arnold G. 1909. The nucleolus and microchromosomes in the spermatogenesis of Hydrophilus piceus (Linn.). Archiv fur Zellforschung 2: 181 - 188.","Asana JJ, Makino S, Niiyama H. 1942. A chromosomal survey of some Indian insects IV. On the sex chromosomes of some species of beetles (Coleoptera). Cytologia 12: 187 - 205.","Smith SG. 1953. Chromosome numbers of Coleoptera. Heredity 7: 31 - 48.","Agarawal U. 1960 a. Chromosome number and sex mechanism in sixteen species of Indian Coleoptera. Current Science 29: 140."]}

GENUS NOTEROPAGUS DʼORCHYMONT, 1919 (FIG. 14A–B, G) Material examined: Noteropagus sp.: (unidentified species illustrated in Fig. 14G). 1 male (NMPC): Taiwan: Nantou County, Yushan National Park, Dongbu Scenic Area, Dong Bu 5.4 km SE of Heshe, rotten banana trunks on the margin of a village, 23.5610°N 120.93044°E, 15.v.2018, M. Fikáček, W.-R. Liang, H.-C. Liu & Y. Minoshima lgt. (2018-TW33). Karyotype: 2 n = 22. Two nuclei from testis show probably the meiotic metaphase I with 11 bivalents. The sex bivalent cannot be recognized, although the smallest element in Figure 14A appears asymmetrical. The remaining bivalents suggest that the autosomes are all more or less similar in size., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS ADOLOPUS SHARP, 1884 (FIG. 12A–C) Material examined: Adolopus sp. 1: 4 males, 3 females (NMPC): New Zealand: Stewart Island, Northwest Circuit Tk. at Kaipipi Bay, rotten longs/twigs in sparse hardwood forest with tree ferns, 46°53.88’S 168°4.31’E, 20 m a.s.l., 21.i.2016, M. Seidel & M. Fikáček lgt. (2016- NZ 017). Adolopus sp. 2: 1 male (NMPC): New Zealand, Waikato (WO), Pirongia Forest Park, Ruapane Link Track (lower part), 37.966°S 175.144°E, 235 m, 18– 21.xi.2016, M. Fikáček & M. Seidel lgt. (MM02). Karyotype: 2 n = 22 + Xy (♂). In the Kaipipi Bay species (Fig. 12B), autosome pair 1 is the longest, and remaining autosomes gradually decrease in length so that pair 11 is about a quarter of the length of pair 1. All autosomes are metacentric to submetacentric. The X chromosome is metacentric, about as long as autosome pair 5, and the Y chromosome is dotlike. Adolopus from Pirongia (Fig. 12A) differs from that of Kaipipi Bay by subacrocentric pairs 7–9 and the acrocentric X chromosome slightly longer than autosome pair 2. Note: The identification of the examined specimens is impossible at the moment; however, the DNA data (Seidel, unpubl.) indicate that they represent two different species., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS COELOSTOMA BRULLÉ, 1835 (FIG. 15A–C, H) Material examined: Coelostoma orbiculare (Fabricius, 1775): 1 male, 2 females (BMNH): United Kingdom, Norfolk, East Walton, R. Angus & F. Shaarawi lgt. Karyotype: 2 n = 26 + Xy (♂). The autosomes and the X chromosome are metacentric to submetacentric with strong centromeric C-bands. Autosome pair 6 has a distinct subterminal secondary constriction on its long arm. The Y chromosome is dot like, and there may be two small B-chromosomes in the examined specimens. All the nuclei are from eggs taken from a cocoon spun by one of the females. In total, 16 male and 6 female nuclei were photographed. The two small B-chromosomes were present in only one male nucleus., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS ANACAENA THOMSON, 1859 (FIG. 7A–D) Material examined: Anacaena gaetanae Bameul, 2001: 1 female (BMNH): France, Corsica, Corse du Sud, R. Stabiacciu, Porto Veccio, 12.vii.2009, R. B. & E.M. Angus lgt. (BMNH). Anacaena lutescens (Stephens, 1829): 3 female specs. (BMNH): Germany, Hamburg district, 16.iv.1988, R. Angus lgt.; 1 spec. (BMNH): United Kingdom, Norfolk, R. Angus lgt. Karyotype: The karyotype of A. gaetanae (Fig. 7A) is similar to that of bisexual A. lutescens (2 n = 16 + Xy p (♂)) but the chromosome taken to be the X is noticeably larger. Comments on karyotypes: The karyotypes are discussed in detail by Shaarawi & Angus (1991a). Parthenogenetic A. lutescens is heterozygous for loss of a small apical section of chromosome 8, distal to a secondary constriction (Fig. 7C). Anacaena globulus (Paykull, 1798) has a fusion of two chromosomes (autosomes) to give a reduction from eight to seven pairs (2 n = 14 + Xy p). Anacaena rufipes (Guillebeau, 1896) has two further fusions, one involving the X chromosome, to give five pairs of autosomes and neo-XY sex chromosomes (2 n = 10 + neo-XY). Shaarawi & Angus (1991a) suggested that the original small Y chromosome had also fused with the neo-Y chromosome, but it is also possible that it has simply been lost. Triploidy (3 n = 27) was found in two widely separated populations of A. lutescens, from the United Kingdom (Armathwaite, Cumbria) and the Netherlands (Doetinchem, Gelderland). In both cases diploid females were also present. In the triploids there was one pair of intact chromosome 8 and one extra chromosome 8 with the deletion. In the Armathwaite population, one of three replicates of chromosome 8 has a pericentric inversion and is acrocentric., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134, {"references":["Shaarawi FAI, Angus RB. 1991 a. Chromosomal analysis of some European species of the genus Berosus Leach (Coleoptera Hydrophilidae). Koleopterologische Rundschau 61: 105 - 110."]}

GENUS STERNOLOPHUS SOLIER, 1834 (FIG. 6I–K) Material examined: Sternolophus solieri Castelnau, 1840: 1 male (BMNH): Egypt, surroundings of Cairo, 10 th Ramadan, R. Angus lgt. Karyotype: 2 n = 16 + Xy (♂). Chromosomes 1–7 metacentric, 8 subacrocentric, with an even decrease in length along the karyotype. X chromosome is metacentric, as large as chromosome 1. Note: Agarwal (1960a) provides a meioformula n = 8 + Xy p (♂) for Sternolophus rufipes (Fabricius, 1792), which agrees with the data presented here., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS OMICROGITON DʼORCHYMONT, 1919 (FIG. 14C–D, H) Material examined: Omicrogiton insularis dʼ Orchymont, 1919: 1 male, 1 female (BMNH): Taiwan, 4.8 km SEE of Tonglin, Beikeng Creek Trail, 24.04791°N 120.78434°E, 3.x.2018, rotten banana stem, M. Fikáček, H.-C. Liu, F.-S. Hu & W.-R. Liang lgt. Karyotype: 2 n = 24 + Xy (♂). Autosome pairs 1–3 and the X chromosome are metacentric and clearly larger than the other pairs. Pairs 4 and 7–12 are subacrocentric to acrocentric, and the smallest autosome is about a quarter the length of the largest. The Y chromosome is dot like., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS EXYDRUS BROUN, 1886 (FIG. 13A, D, I) Material examined: Exydrus gibbosus Broun, 1886: 1 female (NMPC): New Zealand: Wellington (WL), Tararua Range, 1 km W of Titurea Dam, start of Greens Rd., 40.4295°S 175.66064°E, 145 m, 26.xi.2016, fragment of broadleaf forest with sparse understory with ferns and Pandanus Parkinson: sifting, M. Fikáček & M. Seidel lgt. (MM31). Karyotype: 2 n = 30 (♀). The only nucleus obtained has 29 chromosomes and the karyogram shows a serious size mismatch in pair 3 so there should be at least 30 chromosomes in the karyotype, presumably 14 pairs of autosomes plus the sex chromosomes. The smallest chromosome appears heavy and almost single-stranded; however, this is almost certainly because the two chromatids of a metacentric are lying on top of each other. This is frequent with small chromosomes. There is gradual decrease in length along the karyotype, with no pair strikingly longer than the others. The smallest pair is about a third of the length of the longest pair. Most of the chromosomes are metacentric or submetacentric; however, pairs 6–9 are subacrocentric., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS LIMNOHYDROBIUS REITTER, 1909 (FIG. 5A–E) Material examined: Limnohydrobius convexus (Brullé, 1835): 2 spec. (BMNH): France, Corsica, R. Angus lgt.; 2 spec. (BMNH): Spain, Menorca, G. Foster lgt. (BMNH). Karyotype: 2 n = 16 + Xy(♂).Chromosomes1,3–5,8and X showing weak centromeric C-bands. Chromosomes 1–6 metacentric, 7, 8 and X submetacentric with X large, about as long as chromosome 5. Note: Limnohydrobius was recently separated from Hydrobius based on DNA-based phylogenetic data (Short et al., 2017); previously Limnohydrobius species were classified under the latter genus (e.g. Hansen, 1999)., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134, {"references":["Short AEZ, Cole J, Toussaint EFA. 2017. Phylogeny, classification and evolution of the water scavenger beetle tribe Hydrobiusini inferred from morphology and molecules (Coleoptera: Hydrophilidae: Hydrophilinae). Systematic Entomology 42: 677 - 691.","Hansen M. 1999. World catalogue of insects. Volume 2. Hydrophiloidea (s. str.) (Coleoptera). Stenstrup: Apollo Books."]}

GENUS PARACYMUS THOMSON, 1867 (Fig. 3A–H) Material examined: Paracymus aeneus (Germar, 1824): 2 spec. (BMNH): United Kingdom, England, Isle of Wight, R. Angus lgt. Paracymus scutellaris (Rosenhauer, 1856): 2 spec. (BMNH): United Kingdom, England, Hampshire, New Forest, R. Angus lgt. Karyotype: 2 n = 16 + Xy p (♂). No C-banding was attempted. Autosome 1 is distinctly longer than the others and X is the shortest (apart from y) in both species., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134

GENUS LACCOBIUS ERICHSON, 1837 (FIG. 2F–L) Material examined: Laccobius (Compsolaccobius) decorus (Gyllenhal, 1827). 2 males. (BMNH): Sweden, Öland Island, R. Angus lgt. Karyotype: 2 n = 16 + Xy p (♂). Centromeric C-bands strong. All autosomes, and X chromosome, metacentric. Autosomes similarly sized, X chromosome the largest in the nucleus. Comments on karyotypes of Laccobius: Angus & Shaarawi (1997) published the karyotype data of two species of the subgenus Laccobius [Laccobius colon (Stephens, 1829) and Laccobius minutus (Linnaeus, 1758)] and four species of the subgenus Dimorpholaccobius [Laccobius bipunctatus (Fabricius, 1775), Laccobius sinuatus Motschulsky, 1849, Laccobius striatulus (Fabricius, 1801) and Laccobius ytenensis Sharp, 1910]. Laccobius karyotypes all show 2 n = 16 + Xy p (♂). All autosomes and the X chromosome have strong centromeric C-bands, which are particularly strong in Laccobius striatulus and Laccobius sinuatus., Published as part of Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, pp. 958 in Zoological Journal of the Linnean Society 192 (3) on page 958, DOI: 10.1093/zoolinnean/zlaa105, http://zenodo.org/record/5301134, {"references":["Angus RB, Shaarawi FAI. 1997. Chromosomal analysis of Chaetarthria seminulum (Herbst) and six European species of Laccobius Erichson (Coleoptera: Hydrophilidae). Koleopterologische Rundschau 67: 181 - 186."]}

Laccobius (Microlaccobius) fragilis Nakane, 1966 Ḏ弱flǿ牙ḃ (Fig. 18) Laccobius (Microlaccobius) fragilis Nakane, 1966: 57. Laccobius (Microlaccobius) fragilis: Gentili (2003: 422) (records from Taiwan). Material examined. No specimens were examined. Published record: Taitung (Gentili 2003). Distribution. China (Gansu, Liaoning, Shaanxi), Japan (Honshu, Shikoku, Kyushu), Korea, Russia,? Taiwan (Gentili 2003; Nakajima et al. 2020; Przewoźny 2020). Comments. The first and so far the only record of this species from Taiwan is a male from Taitung (southern Taiwan) mentioned by Gentili (2003). This species is very similar to L. formosus, and can be differentiated by the narrower median lobe of the aedeagus (Fig. 18). We did not find any specimens of L. fragilis in this study, although we also examined specimens from Taitung. The occurrence of L. fragilis in Taiwan hence needs to be reconfirmed. However, more species usually co-occur at localities sampled by us in Taiwan and we hence cannot exclude that L. fragilis may be rare and hence unrecorded by us. Therefore, we still maintain L. fragilis as a member of Taiwanese fauna., Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on page 590, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Nakane, T. (1966) New or little known Coleoptera from Japan and its adjacent regions, XXIII. Fragmenta Coleopterologica, 14, 55 - 58.","Gentili, E. (2003) Hydrophilidae: III. Additional noteson the genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water beetles of China, Volume 3. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 411 - 429. [vi + 572 pp.]","Nakajima, J., Hayashi, M., Ishida, K., Kitano, T. & Yoshitomi, H. (2020) Aquatic Coleoptera and Hemiptera of Japan. Bun-ichi Sogo Shuppan, Tokyo, 351 pp.","Przewozny, M. (2020) Catalogue of Palearctic Hydrophiloidea (Coleoptera). Internet version 2020 - 01 - 01. Available from: http: // www. waterbeetles. eu (accessed 9 April 2020)"]}

Laccobius (Microlaccobius) hoi Liu & Fikáček sp. nov. 何氏flǿ牙ḃ (Figs 1–5, 21, 25) Type locality. Taiwan, Pingtung County, Ligang Township [¶ffiė], Erchong River [二AEë], 22.7982°N 120.5011°E, 32 m a. s. l. Type material. Holotype: male (NMNS): TAIWAN: PINGTUNG: Ligang Township, Erchong River, 22.7982°N 120.5011°E, 32m, 26.IV.2020. Hsing-Che Liu leg. Paratypes: TAIWAN: PINGTUNG: 1 spec. (HCLC): same data as the holotype. CHIAYI: 1 male, 1 female (NCHU): Dapu Township [k埔ė], Zengwen Dam [曾Ý水庫], 17.V.2020. Kunta Ho leg. by light trap. KAOHSIUNG: 1 female (HCLC): Liouguei District [六AE區], Laonong River [Ž濃ë], 24.VI.2020. Hsing-Che Liu & Uitsiann Ong leg. TAICHUNG: 3 spec. (TARI) Wufeng District [Ȃ峰區], 15.V.2020. Hsing-Che Liu leg. Description. Form and Color (Figs. 1–2). Body length 2.5–2.7 mm (holotype: 2.6 mm), maximum body width 1.7–1.9 mm (holotype: 1.9 mm). Body oval, moderately convex. Maxillary palpus light brownish yellow, blackish at the very apex of the last palpomere. Antennae yellowish to brown, antennal club slightly darker. Head black, with distinct preocular spots. Labrum and mentum black. Pronotum pale, with irregularly shaped central dark spot ca. as wide as three-fifths of pronotum width (Fig. 21). Elytra pale, with variable pattern of slightly irregular longitudinal series consisting of black spots. Whole scutellar shield black. Ventral surface black with yellowish pubescence. Leg pale yellowish. Head. Surface densely punctate, sagittal suture indistinct. Eyes moderately large, somewhat protruding, separated by ca. 2.0× the width of one eye. Labrum coarsely punctate, anterior margin not emarginate. Mentum glabrous, ca. 1.2–1.3× as wide as long. Antennae with 8 antennomeres, longer than maxillary palpus, intermediate segments (antennomeres III and IV) very short; each club antennomere of different shape, closely segmented, with long or short pubescence; antennomere VI largest, antennomere VII semicircular in shape, antennomere VIII longer than wide, tapering towards apex. Thorax. Pronotum ca. 2.6× wider than long; surface rough, loosely punctate. Surface of mesoventrite densely pubescent. Metanepisterna ca. 5.3× as long as wide, parallel-sided; metaventrite densely pubescent except along midline, slightly raised. Scutellar shield in form of equilateral triangle. Elytral surface with slightly irregular rows of serial punctures. Legs. Profemora densely pubescent basally; protibiae with longest stiff setae situated in apical third. Mesofemora almost bare, with sparse punctation; mesotibiae with longitudinal rows of stiff setae. Metafemora smooth, wider than mesofemora; metatibiae slender, slightly bent inwards. Abdomen. Ventrites I–V sparsely pubescent; Ventrite VI densely pubescent. Male genitalia (Figs. 3–5). Aedeagus 0.6 mm long, phallobase slightly narrowed and truncate basally. Median lobe very broad, slightly shorter than parameres, narrowing and membranous at apex, surface with lateral deep rugae. Parameres flattened laterally, very narrow and slightly bent inwards in dorsal and ventral views, strongly narrowing and acute in lateral view. Differential diagnosis. This species is very similar Laccobius philipinus Gentili, 2005, but can be distinguished from it by the pronotal dark spot almost as wide as the head (narrower than the head in L. philipinus; Fig. 6), median lobe very wide and almost of the same width throughout except at apex (median lobe moderately wide, indistinctly constricted subapically in L. philipinus), parameres very narrow, bent inwards, rounded at apex in dorsal and ventral views (parameres moderately wide, straight and pointed at apex in dorsal and ventral views in L. philipinus). For comparison with the aedeagus of the holotype of L. philipinus, see Figs 7–9. Etymology. The species is named after Mr. Kunta Ho who first discovered this species in Pingtung county, Taiwan. Distribution. This species is known from central and southern Taiwan (Chiayi, Kaohsiung, Pingtung, Taichung; Fig. 27). Bionomics. Specimens from Pingtung and Kaohsiung were collected from a lowland stream and co-occurred syntopically with L. formosus and L. roseiceps (Fig. 25). Specimens from Chiayi were collected in a light trap set near a water reservoir. Specimens from Taichung were collected from a small stream and co-occurred syntopically with L. hammondi (Fig. 24), but L hoi sp. nov. was much less abundant than L. hammondi. Comments. Gentili (2005) described L. philipinus from the Philippines, but included a single female from Taiwan in the type series. The Taiwanese specimen was collected in Liukui near Kaohsiung. The first author of this study (HCL) visited the area in 2020 and collected the Hydrophilidae from streams and wet rocks in Liukui and surrounding areas in the Kaohsiung county. Three species of Laccobius were found: L. formosus, L. roseiceps and L. hoi sp. nov., but no specimens of L. philipinus. Laccobius philipinus and L. hoi sp. nov. are very similar externally, despite their male genitalia which differ obviously between the species (see differential diagnosis). The paratype of L philipinus from Taiwan designated by Gentili (2005) is deposited in the collection of Elio Gentili in Museo Civico di Storia Naturale, Verona, Italy, and was not examined by us. It seems to correspond to L. hoi sp. nov. by the size of the pronotal dark spot (E. Gentili, pers. comm. July 2020). Therefore, we remove L. philipinus from the Taiwanese fauna., Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on pages 592-594, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Gentili, E. (1979) I Laccobius della regione orientale (Coleoptera, Hydrophilidae). Annuario Osservatorio di Fisica Terrestre e Museo Antonio Stoppani del Seminario Arcivescoville di Milano (New Series), 1, 27 - 50.","Gentili, E. (2005) The genus Laccobius Erichson, 1837 in the Australian region (Coleoptera, Hydrophilidae). In: Daccordi, M. & Giachino, P. M. (Eds.), Results of the zoological missions to Australia of the Regional Museum of Natural Sciences of Turin, Italy. Volume II. Monografie del Museo Regionale di Scienze Naturali Torino, 42, 317 - 370."]}

Laccobius (Microlaccobius) formosus Gentili, 1979 台灣flǿ牙ḃ (Figs 11, 15, 19, 23) Laccobius (Microlaccobius) formosus Gentili, 1979: 48. Material examined. TAIWAN: TAITUNG: 1 male, 3 females, (NMNS): Lanyu [ae嶼], Yonghsing, 17-19.VIII.1998. H.T.Shih & K.W.Huang. L.I.T, [specimens NMNS ENT 3209-1094, 3209-1690, 3209-1141, 3209-1403]; 1 male, (NMNS): Donghe [東河], Jindonglai Forest Road, 4.VIII.2012, Y. T. Wang leg, Light. KAOHSIUNG: 1 male, 6 spec., (NMNS): Liukuei, Shanping [Oi平], 22-23.IV.2004. C.S.Lin & W.T.Yang, UV light trap, [specimens NMNS ENT 4409-723, 4409-737, 4409-712, 4409-919, 4409-734, 4409-709, 4409-711]; 1 male, (HCLC): Liouguei District [六 AE區], Laonong River [Ž濃ë], 22.996017°N 120.638178°E, 229m, 24.VI.2020. Hsing-Che Liu & Uitsiann Ong leg. HSINCHU: 1 male, 1 female, (HCLC): Hengshan Township [DZ山ė], Youluo Stream [油ǎë], 24.714584°N 121.141335°E, 172 m, 14.II.2019. Hsing-Che Liu leg. NANTOU: 1 males, 5 spec., (NMNS): Puli Township [埔¶ D], Meixi [眉ë], 23.988475°N 121.017601°E, 536m, 12.II.2020. Hsing-Che Liu leg.; 9 spec., (NMPC) 4.4 km W of Puli Township start of the Shikeng Road, 530 m 23.988000, 121.017833 15.II.2020. Fikáček, Hu, Liang & Liu lgt. (2020-TW003). PINGTUNG: 1 spec., (TARI): Neipu [內埔], 26.II.2020. Y.-T. Chung leg.; 1 male, 2 spec., (HCLC) Ligang Township [¶ffiė], Erchong River [二AEë], 22.7982°N 120.5011°E, 32m, 26.IV.2020. Hsing- Che Liu leg. TAINAN: 1 male, (HCLC): Zuozhen District [左D區], Jiaotan [m潭], 23.V.2020. by light trap, Kunta Ho & Wei-Chai Wang leg. TAICHUNG: 8 spec. (NMPC): Heping distr,, Bashianshan Mts., Dajiaxi River at Songhe village, 24.17996°N 120.98233°E, 665 m, 5.i.2018, stony river partly with gravel banks: in fine gravel below stones and in green algae mats at the side of the river, Fikáček, Liang & Hsiao lgt. (2018-TW01); 1 spec. (NMPC): Heping distr., Xueshankengxi River E of Taoshan village, 24.32684°N 120.95377°E, 743 m, 6.i.2018, in gravel and among algae at side of a large stony river, Fikáček, Liang, Hsiao lgt. (2018-TW06). Published records. Taihoku [= Taipei] (Gentili 1979). Chipon [= Taitung County]; Kaohsiung; Heito [= Pintung County]; Hualien; Ilan [= Yilan] (Gentili 1989, 1995); New Taipei (Gentili 2003). Diagnosis. Body size 2.2–2.7 mm, body width 1.6–1.9 mm. Body oval (Fig. 11). head black with preocular yellowish spots, Antennae with 8 antennomeres. Pronotum pale, with a large slightly metallic central dark spot (Fig. 19). Elytra surface pale, with dense slightly irregular series of dark spots. Male genitalia (Fig. 15): Aedeagus 0.7 mm long. Median lobe slender, rounded and membranous at apex; parameres much longer than median lobe, apex widely rounded and membranous, truncate inwards. Differential diagnosis. Laccobius formosus Gentili, 1979 is very similar to L. fragilis Nakane, 1966, from which it only differs in the median lobe broadly rounded at apex. Distribution. China (Gansu, Guandong, Guangxi, Hainan, Hubei, Hunan, Jiangxi, Liaoning, Sichuan, Shaanxi, Shandong), Russia (Far East), Taiwan (Fig. 27) (Przewoźny 2020, this paper). In Taiwan, L. formosus is distributed throughout the main island. Bionomics. All specimens were collected from stony streams (Fig. 23)., Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on pages 588-590, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Gentili, E. (1979) I Laccobius della regione orientale (Coleoptera, Hydrophilidae). Annuario Osservatorio di Fisica Terrestre e Museo Antonio Stoppani del Seminario Arcivescoville di Milano (New Series), 1, 27 - 50.","Gentili, E. (1989) Alcune novita sul genere Laccobius (Coleoptera, Hydrophilidae). Annuario Osservatorio di FisicaTerrestre e Museo Antonio Stoppani del Seminario Arcivescovile di Milano (New Series), 10, 31 - 39.","Gentili, E. (1995) Hydrophilidae 3. The genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water Beetles of China, Volume 1. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 245 - 286. [410 pp.]","Gentili, E. (2003) Hydrophilidae: III. Additional noteson the genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water beetles of China, Volume 3. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 411 - 429. [vi + 572 pp.]","Nakane, T. (1966) New or little known Coleoptera from Japan and its adjacent regions, XXIII. Fragmenta Coleopterologica, 14, 55 - 58.","Przewozny, M. (2020) Catalogue of Palearctic Hydrophiloidea (Coleoptera). Internet version 2020 - 01 - 01. Available from: http: // www. waterbeetles. eu (accessed 9 April 2020)"]}

Laccobius (Microlaccobius) hammondi Gentili, 1984 úẍ德flǿ牙ḃ (Figs 12, 16, 20, 24) Laccobius (Microlaccobius) hammondi Gentili, 1984: 31 Laccobius (Microlaccobius) hammondi Gentili (1989: 39) (records from Taiwan). Material examined. TAIWAN: MIAOLI: 1 male, (NMNS): Shihyan, Chuanming Farm, 21-22.VIII.2000. S.H.Ku, UV light, [specimen NMNS ENT 3443-165]. NANTOU: 13 spec. (NMPC): Heshe, Xinyi Township Tongfu Village, at bridge over Heshexi 23.58767°N 120.89027°E. 16.V.2018. Fikáček, Hu, Liang, Liu & Minoshima, lgt. (2018- TW35a); 2 males, 4 females, (NMNS): Jenai, Meifeng, 7-8.VI.1998. C.S.Lin & W.T.Yang, UV light, [specimens NMNS ENT 2948-82, 2948-120, 2948-268, 2948-412, 2948-468, 2948-655]. NEw TAIPEI: 2 spec., (NMNS): Wulai [Ḅ來], Tunghou, 3.VII.2011. Y.-T.Wang leg.; 1 male (NMPC): Wulai City at Wulai Bridge, 24.86404°N 121.5518°E, 18.v.2018, in gravel at sides of Tǒnghòuxî river just above Wulai Bridge, Fikáček & Minoshima lgt. (2018-TW09). YILAN: 3 females, (HCLC): Jiaoxi Township [ẽëė], 24.828770°N 121.752787°E, 44m, 2.VII.2019. H.-C. Liu & F.-S. Hu leg. TAICHUNG: 1 male, 12 spec., (HCLC): Qingtonglin [û桐ẇ], 31.I.2019. Hsing-Che Liu leg.; 1 male, (HCLC): Wufeng District, Qingtonglin Ecological Park [û桐ẇlDz公園], 24.048625°N 120.784559°E, 330m, 26.V.2019, Hsing-Che Liu leg.; 45 spec., (HCLC): Wufeng District, 15.V.2019, Hsing-Che Liu leg. by uv light trap.; 9 spec. (NMPC): Heping distr,, Bashianshan Mts., Dajiaxi River at Songhe village, 24.17996°N 120.98233°E, 665 m, 5.i.2018, stony river partly with gravel banks: in fine gravel below stones and in green algae mats at the side of the river, Fikáček, Liang & Hsiao lgt. (2018-TW01); 4 spec. (NMPC): Heping distr., Xueshankengxi River E of Taoshan village, 24.32684°N 120.95377°E, 743 m, 6.i.2018, in gravel and among algae at side of a large stony river, Fikáček, Liang, Hsiao lgt. (2018-TW06). HSINCHU: 2 males, 1 female, (HCLC): Hengshan Township [DZ山 ė], Youluo Stream [油ǎë], 24.714584°N 121.141335°E, 172m, 14.II.2019. Hsing-Che Liu leg. Published records. Hualien; Ilan [= Yilan]; Nantou (Gentili 1989, 1995). Hsinchu; New Taipei (Gentili 2003). Diagnosis. Body length 2.0– 2.7 mm, maximum body width 1.4–1.9 mm. Body oval (Fig. 12). head black, with distinct preocular spots (some specimen without pale spots). Pronotum black, with densely punctate and pale margins (Fig. 20). Elytra surface pale, with rows of serial dark spots. Male genitalia (Fig. 16): Aedeagus 0.6 mm long, strongly sclerotized. Median lobe shorter than parameres, widening at midlength, apex subtruncate; parameres weakly narrowing, bent inward in apical third. Differential diagnosis. Laccobius hammondi very similar to the Japanese L. oscillans, it can be differentiated by the pronotum almost entirely dark and median lobe more dilated at the apical third than L. oscillans. Distribution. China (Beijing, Fujian, Gansu, Guangdong, Guizhou, Guangxi, Hubei, Hunan, Jiangxi, Liaoning, Sichuan, Shaanxi, Shandong), Taiwan (Fig. 27) (Gentili 1995; Jia et al. 2013a; Przewoźny 2020, this paper). Bionomics. Examined specimens were collected at sides of stony streams and rivers (Fig. 24), and rarely also on sun-exposed algal mats together with Hydroscapha takahashii Miwa, 1934 (see photos in Fikáček et al. 2020) or by light trap. Comments. Preliminary analyses of cox1 sequences of few Taiwanese specimens revealed that Taiwanese specimens identified as L hammondi may in fact represent two distinct species. We observed a slight variation of the aedeagus morphology in our samples, with the median lobe more or less widened, and slightly to apparently shorter than parameres. These observations are based on non-sequenced specimens and we are hence unable to evaluate at the moment whether this variation corresponds to the two molecular lineages or represents an intraspecific variation. A more careful analysis of the situation is needed, based on larger number of specimens sampled across Taiwan, and ideally also including specimens of L. hammondi and related species from China and Japan. We temporarily treat all examined specimens under L. hammondi, despite it may in fact be a complex of species., Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on pages 591-592, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Gentili, E. (1989) Alcune novita sul genere Laccobius (Coleoptera, Hydrophilidae). Annuario Osservatorio di FisicaTerrestre e Museo Antonio Stoppani del Seminario Arcivescovile di Milano (New Series), 10, 31 - 39.","Gentili, E. (1995) Hydrophilidae 3. The genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water Beetles of China, Volume 1. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 245 - 286. [410 pp.]","Gentili, E. (2003) Hydrophilidae: III. Additional noteson the genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water beetles of China, Volume 3. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 411 - 429. [vi + 572 pp.]","Jia, F. - L., Gentili, E. & Fikacek, M. (2013 a) The genus Laccobius in China: new species and new records (Coleoptera: Hydrophilidae). Zootaxa, 3635 (4), 402 - 418. https: // doi. org / 10.11646 / zootaxa. 3635.4.4","Przewozny, M. (2020) Catalogue of Palearctic Hydrophiloidea (Coleoptera). Internet version 2020 - 01 - 01. Available from: http: // www. waterbeetles. eu (accessed 9 April 2020)","Fikacek, M., Hu, F. - S., Aston, P., Jia, F. - L., Liang, W. - R., Liu, H. - C. & Minoshima, Y. N. (2020) Comparative morphology of immature stages and adults of Hydroscapha from Taiwan, with description of a new species from Hong-Kong (Coleoptera: Myxophaga: Hydroscaphidae). Raffles Journal of Zoology, 68, 334 - 349. https: // doi. org / 10.26107 / RBZ- 2020 - 0051"]}

Key to Taiwanese species of Laccobius 1. Eyes kidney-shaped (reniform). Antenna with 7 antennomeres (subgenus Glyptolaccobius). Legs brown. Inhabits wet rocks (Fig. 26).......................................................................... L. politus Gentili, 1979 - Eyes rounded. Antenna with 8 antennomeres (subgenus Microlaccobius). Legs pale yellowish. Inhabits sides of streams or ponds or sun-exposed algal mats (Figs. 23–25).............................................................. 2 2. Body small (1.7–2.2 mm), elongate oval. Pronotum with a small central dark oval spot which is narrower than the width of the head (Fig. 22)................................................................. L. roseiceps Régimbart, 1903 - Body larger (2.0– 2.8 mm), oval. Pronotum with much bigger dark spot, as wide as head or wider...................... 3 3. Parameres widened and membranous apically, median lobe distinctly shorter than parameres.......................... 4 - Parameres slender, bent inward in apical third, median lobe slightly shorter than parameres or as long as parameres....... 5 4. Median lobe wider, apical broadly rounded (Fig. 15)..................................... L. formosus Gentili, 1979 - Median lobe narrower, apical strongly narrowing (Fig. 18)................................. L. fragilis Nakane, 1966 5. Pronotum with a dark spot slightly wider that the head (Fig. 22). Median lobe of the aedeagus very broad, moderately narrowing apically (Fig. 3–4), Parameres very narrow in dorsal and ventral views (Fig. 5).......................... L. hoi sp. nov. - Pronotum almost entirely dark, with pale lateral margins (Fig. 20). Median lobe of the aedeagus widening in the midlength, apex subtruncate. Parameres narrow in dorsal view (Fig. 16).............................. L. hammondi Gentili, 1984, Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on page 596, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Gentili, E. (1979) I Laccobius della regione orientale (Coleoptera, Hydrophilidae). Annuario Osservatorio di Fisica Terrestre e Museo Antonio Stoppani del Seminario Arcivescoville di Milano (New Series), 1, 27 - 50.","Nakane, T. (1966) New or little known Coleoptera from Japan and its adjacent regions, XXIII. Fragmenta Coleopterologica, 14, 55 - 58."]}

Laccobius (Glyptolaccobius) politus Gentili, 1979 光澤flǿ牙ḃ (Figs 10, 14, 26) Laccobius (Microlaccobius) politus Gentili, 1979: 46. Laccobius (Cyclolaccobius) politus: Gentili (1995: 257); Gentili (2003: 414); Hansen (1999: 132). Oocyclus flaveolus Hebauer & Wang, 1998: 41. Synonymized with L. politus by Gentili (2012). Laccobius (Glyptolaccobius) politus: Jia et al (2019: 72). Material examined. TAIWAN: NANTOU: 7 spec., (NMPC): 5.5 km SSW of Heshe at Rd. 07 23.55263°N 120.86947°E, 1070m. 16.V.2018. Fikáček, Liang, Liu & Minoshima. (2018-TW37); 15 spec., (NMPC): wet concrete wall at Kaigao Rd. 4.25 km SE of Heshe; 23.5641°N 120.91837°E. 15.V.2018. Fikáček, Liang, Liu & Minoshima. (2018-TW34); CHIAYI: 1 spec., (NMPC): track down to Yuntan waterfall 3.5 km W of Meishan township 23.5327417, 120.6557500; 850m 1.v.2019; Damaška, Fikáček, Liu & Tkoč lgt. (2019-TW13). NEw TAIPEI: 1 male, 3 spec. (HCLC, NCHU): Pingxi District, Wanggu Waterfall [望古瀑布], 30.III.2020. on the wet rock, Hsing-Che Liu leg. HSINCHU: 2 males, 5 spec., (HCLC): Emei Township [峨眉ė], Qixing Village [七ffl村], 24.656664°N 121.023909°E, 151m, 24.VIII.2020. on wet rock, Hsing-Che Liu leg. TAICHUNG: Heping distr, Bashianshan Mts., beginning of Bashianshan Forest Rd., 5.i.2018 24.19808°N 121.00115°E, 722 m, exposed wet concrete/stony wall at side of the road, Fikáček, Liang, Hsiao (2018-TW03). Published records: New Taipei (Gentili 1979, 2003; Hebauer & Wang 1998); Hualien (Gentili 1995); Keelung, Kaohsiung (Hebauer & Wang 1998); Nantou (Gentili 2003, 2012). Diagnosis. Body length 1.8–2.0 mm, maximum body width 1.2–1.3 mm. Body oval (Fig. 10), strongly convex. Dorsal back, pronotum and elytra with lateral dark brown margin. Surface of pronotum and elytra with sparse white setae. Legs brown. Male genitalia (Fig. 14): Aedeagus 0.5 mm long. Median lobe slender, wide basally, slightly narrowing towards midlength, apical rounded; parameres slightly shorter than median lobe or as long as median lobe, weakly narrowing at apex, narrowing towards basal, basal truncate. Differential diagnosis. Laccobius politus is similar to Chinese species of L. hainanensis Jia, Gentili & Fikáček, 2013, L. martini Jia, Song & Gentili, 2013 and L. motuoensis Jia, Chen & Fikáček, 2019. It can be differentiated from them by the dorsal surface with sparse white setae, median lobe indistinctly constricted subapically, and parameres narrower than median lobe, rounded apically. This species is the only inhabitant of wet rocks in Taiwan, as well as that only representative of the subgenus Glyptolaccobius in Taiwan. Therefore, this species can be easily distinguished from other Taiwanese species. Distribution. China (Yunnan), Nepal, Taiwan (Fig. 27) (Gentili 1979; Gentili 2003; Hebauer 2006; Jia et al. 2013, this paper). Bionomics. All examined specimens were collected on wet rocks (Fig. 26)., Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on page 594, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Gentili, E. (1979) I Laccobius della regione orientale (Coleoptera, Hydrophilidae). Annuario Osservatorio di Fisica Terrestre e Museo Antonio Stoppani del Seminario Arcivescoville di Milano (New Series), 1, 27 - 50.","Gentili, E. (1995) Hydrophilidae 3. The genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water Beetles of China, Volume 1. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 245 - 286. [410 pp.]","Gentili, E. (2003) Hydrophilidae: III. Additional noteson the genus Laccobius Erichson in China and neighbouring areas (Coleoptera). In: Jach, M. A. & Ji, L. (Eds.), Water beetles of China, Volume 3. Zoologisch-Botanische Gesellschaft in Osterreich and Wiener Coleopterologenverein, Wien, pp. 411 - 429. [vi + 572 pp.]","Hansen, M (1999) Hydrophiloidea (Coleoptera). In: Hansen, M. (Ed.), World Catalogue of Insects, Vol. 2. Apollo Books, Stenstrup, pp. 1 - 416.","Hebauer, F. & Wang, L. - J. (1998) New species of the genus Oocyclus Sharp, 1882 from India, Sri Lanka and Taiwan with a key to all known species (Coleoptera: Hydrophilidae). Acta Coleopterologica, 14, 37 - 46.","Gentili, E. (2012) New or poorly known Laccobius of the Subgenus Cyclolaccobius Gentili, 1991 (Coleoptera: Hydrophilidae). Giornale Italiano di Entomologia, 13 (57), 55 - 68.","Jia, F. - L., Chen, J. - H. & Fikacek, M. (2019) 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. ZooKeys, 889, 65 - 80. https: // doi. org / 10.3897 / zookeys. 889.34690","Jia, F. - L., Gentili, E. & Fikacek, M. (2013 a) The genus Laccobius in China: new species and new records (Coleoptera: Hydrophilidae). Zootaxa, 3635 (4), 402 - 418. https: // doi. org / 10.11646 / zootaxa. 3635.4.4","Jia, F. - L., Song, K. - Q. & Gentili, E. (2013 b) A new species of Laccobius Erichson, 1837 from China (Coleoptera: Hydrophilidae). Zootaxa, 3734 (1), 91 - 95. https: // doi. org / 10.11646 / zootaxa. 3734.1.11","Hebauer, F. (2006) New records of Hydrophiloidea from Nepal (Coleoptera: Hydrophilidae). Acta Coleopterologica, 22 (2), 3 - 10."]}

Laccobius (Microlaccobius) roseiceps Régimbart, 1903 RẦflǿ 牙ḃ (Figs 13, 17, 22, 25) Laccobius (Microlaccobius) roseiceps Régimbart, 1903: 59. Material examined. TAIWAN: PINGTUNG: 3 males, 6 females (HCLC): Ligang Township [¶ffiė], Erchong River [二AEë], 22.7982°N 120.5011°E, 32m 26.IV.2019. Hsing-Che Liu. KAOHSIUNG: 1 spec. (HCLC): Liouguei District [六AE區], Laonong River [Ž濃ë], 22.996017°N 120.638178°E, 229m, 24.VI.2020. Hsing-Che Liu & Uitsiann Ong leg. KINMEN: 2 males, 20 spec. (HCLC, NCHU): Main Island, 5-10. VII. 2020, Hsing-Che Liu leg. Diagnosis. Small species, body length 1.7–2.2 mm, body width 1.0– 1.3 mm. Body elongate oval (Fig. 13), weakly convex. Head dark, with distinct preocular spots. Pronotum pale, with small dark oval spot in median, spot leaving large lateral portions of the pronotum yellow. (Figs. 22). Scutellar shield dark. Elytra pale, with densely arranged small dark spots, larger spots present medially and laterally. Leg pale or yellowish. Male genitalia (Fig. 17): Aedeagus 0.4 mm long. Median lobe wide, its apex rounded, with a pair of diverging lines running from apex; parameres slender, larger than median lobe, slightly bent inward. Differential diagnosis. Laccobius roseiceps may be easily recognized by the pronotum with small oval dark spot. In this character, it may resemble L. hoi sp. nov. from which it mainly differs in smaller body size (1.7–2.2 mm in L. roseiceps, 2.5–2.7 mm in L. hoi sp. nov.). The structure of the median lobe (with the diverging lines) is very typical and hard-to-confuse with any other Laccobius species. Distribution. China (Hong Kong), Japan (Honshu, Kyushu, Tanegashima), Taiwan (Kinmen islands) (Nakajima et al. 2020; Przewoźny, 2020, Liu et al. 2021). First record for Taiwan island (Fig. 27). Bionomics. All specimens were collected from very slowly running streams. In southern Taiwan, the species co-occurred syntopically with L. hoi sp. nov. and L. formosus (Fig. 25)., Published as part of Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, pp. 587-599 in Zootaxa 4963 (3) on pages 595-596, DOI: 10.11646/zootaxa.4963.3.11, http://zenodo.org/record/4704278, {"references":["Nakajima, J., Hayashi, M., Ishida, K., Kitano, T. & Yoshitomi, H. (2020) Aquatic Coleoptera and Hemiptera of Japan. Bun-ichi Sogo Shuppan, Tokyo, 351 pp.","Przewozny, M. (2020) Catalogue of Palearctic Hydrophiloidea (Coleoptera). Internet version 2020 - 01 - 01. Available from: http: // www. waterbeetles. eu (accessed 9 April 2020)","Liu, H. - C., Ma, C. - H. & Fikacek, M. (2021) Water scavenger beetles of Kinmen County, Taiwan (Coleoptera: Hydrophilidae). Taiwan Journal of Biodiversity, 32 (1), 39 - 62."]}

Fikáček, Martin, Hu, Fang-Shuo, Aston, Paul, Jia, Feng-Long, Liang, Wei-Ren, Liu, Hsing-Che, Minoshima, Yûsuke N. (2020): Comparative morphology of immature stages and adults of Hydroscapha from Taiwan, with description of a new species from Hong Kong (Coleoptera: Myxophaga: Hydroscaphidae). Raffles Bulletin of Zoology 68: 334-349, DOI: 10.26107/RBZ-2020-0051

Thysanarthria hongsonensis Hebauer, 2001 (Figs 1D, 8 F–J, 11) Thysanarthria hongsonensis Hebauer, 2001: 398. Type material exmined. HOLOTYPE: ♂ (SMNS), THAILAND: MAE HONG SON: ʻThai, N. Mae Hong Son / prov. Soppong env., 600m / 19´27´´N 98´20´´E, 28.5.- / 2.6.1999, D. Hauck leg.’ Additional material examined. THAILAND: MAE HONG SON: 1 ♂, 2 spec. (NHMW, NMPC): Mae Ping, at light, 6.ix.1991, lgt. Malicky; 1 ♂, 1 spec. (NHMW): same locality and collector, 24.–25.vi. 1991. Redescription. Body length 1.5 mm, maximum body width 0.9 mm. Head and labrum black; pronotum dark brown in the middle, becoming weakly paler towards margins; elytra uniformly yellowish; legs yellowish. Head without microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.3× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 8 F–H) 0.5 mm long. Phallobase at the base of parameres slightly widened, but not wider than parameres combined; very slightly constricted more basally, strongly arcuate in lateral view. Parameres narrow and elongate, narrow basally, gradually narrowing into a rather acute apex, outer face of parameres sinuate. Median lobe nearly reaching apex of parameres, narrow, membranous and rounded apically, without paired subapical projections. Differential diagnosis. The species is characterized by a tiny body size, absence of dorsal microsculpture and very characteristic aedeagus with narrow elongate parameres. In narrow parameres it may resemble T. madurensis but may be distinguished from it by sinuate lateral face of parameres (arcuate in T. madurensis), median lobe without paired subapical projections (with the projections in T. madurensis) and only indistinctly widened base of the phallobase (abruptly widened in T. madurensis). Biology. Unknown, most examined specimens were collected at light. Distribution. So far only known from two nearby localities in northern Thailand (Mae Hong Son Province) (HEBAUER 2001)., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on page 244, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Fikáček, Martin, Liu, Hsing-Che (2019): A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini). Acta Entomologica Musei Nationalis Pragae 59 (1): 229-252, DOI: 10.2478/aemnp-2019-0020

Thysanarthria trifida sp. nov. (Figs 6 F–J, 11) Type material. HOLOTYPE: ♂ (NHMB), LAOS: BOLI KHAM XAI: 8 km NE of Ban Nape, 600 m, 1.–18.v.2001, lgt. Pacholátko. PARATYPES: 25 spec. (NHMB, NHMW, NMPC):same data as the holotype; 1♂ (SMNS): Ban Nape, Kaew Nua, 18.iv.1998 – 1.v.1998, lgt. E. Jendek & O. Šauša. Description. Body length 1.9–2.0 mm (holotype 1.9 mm), maximum body width 1.0– 1.1 mm (holotype 1.0 mm). Head and labrum black; pronotum uniformly yellowish or slightly darkened centrally; elytra uniformly yellowish or with slightly darkened striae; legs yellowish. Head with weak granulate microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 2.8× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 6 F–J) 0.6 mm long. Phallobase weakly and gradually narrowing from base of parameres towards base, slightly widened basally, weakly arcuately bent in lateral view; c. 1.5× longer than parameres. Paremeres narrowly elongate, gradually narrowing towards apex, lateral face nearly continuously arcuate, apex bluntly rounded. Median lobe wide at level of gonopore, distinctly constricted basally of it, apex membranous, acutely pointed; subapical part with two triangular membranous lobes; apex reaching c. level of apex of parameres; gonopore transversely oval, situated below bases of paired projections. Differential diagnosis. Thysanarthria trifida closely resembles T. bifida in external characters and genitalia morphology; see under the latter species for diagnostic characters. The other three species with paired subapical projections on the median lobe (T. brincki, T. cardamona and T. madurensis) can be differentiated from T. trifida easily by a very different shape of parameres. Species which may resemble T. trifida in the shape of the parameres (T. championi, T. hongsonensis, T. persica) all lack the paired projection on the median lobe. Etymology. The species name refers to the apex of the median lobe bearing three lobes (the apex plus the pair of subapical projections). We purposely select the name sounding similar to that of T. bifida which is the most similar species to T. trifida. Adjective. Biology. Unknown. Distribution. So far only known from the Ban Nape area in central Laos., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on page 250, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918

Thysanarthria madurensis Hebauer, 2001 (Figs 8 K–O, 11) Thysanarthria madurensis Hebauer, 2001: 398. Type material examined. HOLOTYPE: ♂ (MZLU), SRI LANKA: ʻCeylon, E. Prov. / Madura Oya / 15 mls NNW Bibile / 13.III.62 Loc. 138 // near river // Lund University / Ceylon Expedition 1962 / Brinck-Andersson- / Cederholm // MZLU / Type no. / 3121:1 // Photo 2017 / by MZLU // MZLU / 2017 / 466’. Additional material examined. INDIA: KERALA: 1 ♂ (NHMW): Shoranur, bank of Ponnani river, 31.i.1994, lgt. Z. Kejval. NEPAL: 1 ♂, 2 spec. (SMNS, NMPC): Narayani, Sauraha, Rapti River bank, light trap, 18.iv.2000, lgt. A. Weigel. Redescription. Body length 1.3 mm, maximum body width 0.9 mm. Head and labrum black; pronotum uniformly yellowish; elytra uniformly yellowish; legs yellowish. Head with weak granulate microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 4.0× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with weak granulate microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 8 K–O) 0.4 mm long. Phallobase moderately wide at base of parameres, c. as wide as paramares combined, gradually narrowing towards basal fifth, base abruptly widened, arcuate in lateral view. Parameres narrow and elongate, gradually narrowing towards a pointed apex, apices slightly divergent, outer face of parameres arcuate. Median lobe narrow, not reaching apex of parameres, with a pair of pointed lobes subapically, apex cut off between these projections; gonopore transversely oval, subapical. Differential diagnosis. In the tiny body size, dorsal surface without microsculpture and narrowly elongate pointed parameres, T. madurensis only resembles T. hongsonensis. See under the latter species for diagnostic charactares. Biology. Unknown, the Nepalese specimens were collected at light. Distribution. The species is known from three very distant localities (Sri Lanka, southern India and Nepal). If the label data especially of the Nepalese specimens are correct, the species is likely widely distributed in the Indian peninsula, but overlooked., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 244-246, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Thysanarthria cardamona sp. nov. (Figs 5 F–J, 11) Type material. HOLOTYPE: ♂ (NHMW), INDIA: KERALA: Cardamon Hills, 50 km NW of Pathanamthitta, Pambaiyar river, at light, 6.–9.v.1994, lgt. Z. Kejval. PARATYPES: 9 specimens (NHMW, NMPC): same data as the holotype. Description. Body length 1.4–1.7 mm (holotype 1.4 mm), maximum body width 0.8–1.0 mm (holotype 0.8 mm). Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with weak microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.5× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with weak microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals flat at midlength, weakly convex near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus 0.5 mm long. Phallobase wide at base of parameres (but narrower than bases of parameres combined), strongly constricted at c. midlength into narrowly tubular base, in lateral view slightly bent shortly below parameral bases. Paramere wide basally, strongly narrowing up to the apical third, apical half membranous on outer face; apical part projecting into sharp tooth laterally and narrow rounded lobe mesally. Median lobe membranous, rounded apically, not widening subapically; subapically with a pair of rounded projections; apex not reaching the level of apex of parameres; gonopore transversely oval, situated below the base of paired projections. Differential diagnosis. Thysanarthria cardamona is easy to distinguish by its very characteristic aedeagus which only slightly resembles that of T. brincki; see under the latter species for the differences. Etymology. The species name refers to the Cardamon Hills where the type locality of the species is situated.Adjective. Biology. The type series was collected at light, no more information is available. Distribution. Only known from the type locality., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on page 240, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918

Thysanarthria saurahana sp. nov. (Figs 9 A–E, 11) Type material. HOLOTYPE: ♂ (SMNS): NEPAL: ʻNepal, Narayani, Sauraha, Rapti River bank, light trap, 180, 84.49695, 27.56667, 2000- 04-18, A. Weigel, NEPAL, Prov. Narayani / Sauraha, Rapti River / Ufer, 180mNN, 27°34´80´´N, 84°29´49´´E / LF, 18.IV.2000 / leg. Weigel // Thysanarthria / madurensis / det. F. Hebauer’. Description. Body length 1.7 mm, maximum body width 1.0 mm. Head and labrum black; uniformly yellowish; elytra uniformly yellowish; legs yellowish. Head with strong mesh-like microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 2.7× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with strong mesh-like microsculpture. Elytra with 10 striae sharply impressed except anteromedially (widely around scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 9 A–E) 0.5 mm long. Phallobase slightly widened at base of parameres, c. as wide as parameres combined, slightly narrowed towards basal fifth and abruptly widened at base; arcuate in lateral view. Paramere narrowly elongate, subequal in width throughout, apex abruptly narrowing into a short mesoapical ʻtooth’. Median lobe much shorter than parameres, with strongly sclerotized shorter part arcuate apically, and membranous apical part rounded apically; gonopore large, triangular, situated subapically. Differential diagnosis. Thysanarthria saurahana is the only species in Himalaya with strong mesh-like microsculpture on the pronotum (in contrast to pronotum without microsculpture in T. championi and T. siamensis, and with weak granulate microsculpture in T. madurensis). It can be distinguished from all these species as well as from all other Thysanarthria by the shape of parameres and the unique morphology of the median lobe which is not similar to any other species of the genus. Etymology. The species name refers to the village of Sauraha at the border of the Chitwan National Park in Nepal where the holotype was collected. Adjective. Biology. Unknown. Distribution. Only known from the type locality., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 246-247, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Thysanarthria brittoni Balfour-Browne, 1951 (Figs 4 K–O, 11) Thysanarthria brittoni Balfour-Browne, 1951: 215. Thysanarthria brittoni: HEBAUER (1997: 267, catalogue); HANSEN (1999: 105, catalogue). Type material examined. HOLOTYPE: ♂ (BMNH), ʻType // W ADEN PROT / Wadi at foot of / Jebel Harir / ca. 5,000 ft / 1,2. xi.1937 // B. M. Exp. to / S. W. Arabia / H. Scott & / E. B. Britton / B. M. 1938-246 // J. Balfour-Browne det. / Thysanarthria / brittoni Type!ʼ. Redescription. Body length 1.6 mm, maximum body width 1.0 mm. Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with weak microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.1× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with weak microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; interval punctation sparse, setiferous; interstices without distinct microsculpture. Aedeagus (Figs 4 K–O) c. 0.5 mm long. Phallobase strongly widened at base of parameres, c. as wide as bases of parameres combined, strongly constricted at c. midlength, slightly bent in lateral view. Paremere widely rounded basally, slightly narrowing in apical third, apex rounded, apices divergent from each other. Median lobe narrow, membranous apically, without subapical projections; apex reaching c. level of apex of parameres; gonopore transversely oval, situated in distal third. Variability. BALFOUR- BROWNE (1951) mentions that the dorsal microsculpture of the head and pronotum, which is very weakly developed in the holotype, is stronger in some of the paratypes which are hence externally undistinguishable from T. atriceps. Differential diagnosis and discussion. Thysanarthria brittoni is very similar to T. atriceps in all characters including male genitalia, which only differ in the proportions of the parameres including their slightly diverging apices, and by the more strongly constricted phallobase (see under T. atriceps for details). The difference of the genitalia of T. brittoni from the examined specimens of T. atriceps is bigger than the observed intraspecific variability of T. atriceps, which is the reason why we consider T. brittoni a separate species at the moment. Biology. Unknown. Distribution. Only known from the type locality in western Yemen, Arabian Peninsula (BALFOUR- BROWNE 1951)., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on page 238, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["BALFOUR-BROWNE J. 1951: Coleoptera: Haliplidae, Dytiscidae, Gyrinidae, Hydraenidae, Hydrophilidae. Pp 179 - 220 + pls 10 - 11. In: Expedition to South-west Arabia 1937 - 1938. British Museum (Natural History), London, xiv + 504 pp.","HEBAUER F. 1997: Annotated checklist of the Hydrophilidae and Helophoridae (Insecta: Coleoptera) of the Arabian Peninsula with a description of a new genus and species. Fauna of Saudi Arabia 16: 255 - 276.","HANSEN M. 1999: Hydrophiloidea (s. str.) (Coleoptera). World Catalogue of Insects 2: 1 - 416."]}

Thysanarthria bifida sp. nov. (Figs 6 A–E, 11) Type material. HOLOTYPE: 1 ♂ (NHMW), THAILAND: MAE HONG SON: Mae Ping, at light, 6.i.–30.ix.1991, lgt. Malicky. PARATYPES: 6 specimens (NHMW, NMPC): same data as the holotype. CHIANG MAI: 2 spec. (NHMW): Chiang Mai, Zoo, at light, 18.–25.iv.1988, lgt. Chantaramongkol & Malicky. SONGKHLA: 3 spec. (NHMW): ʻab Ton Nga Chang WF’, 4.–5.v.1993. Description. Body length 1.2–1.5 mm (holotype 1.3 mm), maximum body width 0.8–0.9 mm (holotype 0.9 mm). Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with weak mesh-like microsculpture on interstices; punctation sparse, each puncture bearing a seta. Eyes separated by 4.0× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices smooth, without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus 0.5 mm long. Phallobase weakly and gradually narrowing from base of parameres towards base, slightly widened basally, weakly arcuately bent in lateral view; c. 2× longer than parameres. Paremeres short, wide basally, gradually narrowing towards apex, lateral face nearly continuously arcuate, apex bluntly rounded. Median lobe wide at level of gonopore, indistinctly constricted basally of it, apex membranous, widely rounded; subapical part with two triangular membranous lobes; apex reaching c. level of apex of parameres; gonopore transversely oval, situated below bases of paired projections. Differential diagnosis. Thysanarthria bifida is easy to regonize by the median lobe bearing a pair of subapical membranous projections combined with the short parameres arcuately narrowing into simply rounded apices. In these characters it closely resembles T. trifida sp. nov. from which it mainly differs in smaller body size (1.2–1.5 mm in T. bifida, 1.9–2.0 mm in T. trifida), shorter and wider parameres (compare Figs 6 A–E to 6 F–J) and the membranous apex of the median lobe widely rounded (compared to the pointed one in T. trifida). Etymology. The species name refers to the subapical pair of projections on the median lobe which make the apex of the median lobe seemingly bifid when observed under the microscope. Adjective. Biology. Most examined specimens were collected at light, no more data are available about the biology. Distribution. The species is so far known from three localities, two of which are situated in northwestern Thailand (provinces Mae Hong Son and Chiang Mai) and the last in the southernmost Thailand close to the border with Malaysia (province Songkhla). This indicates that the species is likely quite widely distributed but overlooked and rarely collected., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 238-240, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Chaetarthria sp. (Figs 11, 12 A–K) Material examined. SAUDI ARABIA: 1 ♂ 4 spec. (NMPC): Jizan, Wadi Atoud, 17.8°N 42.366°E, at light, 245 m, 8.ii.2016, lgt. J. Bezděk & D. Král. Diagnosis. Body 1.7–2.0 mm long; head and labrum black; pronotum and elytra uniformly yellowish; legs reddish to yellowish; dorsal surface without microsculpture; setae on dorsal surface peg-like (Figs 12 J–K); elytron without elytral striae except sharply impressed sutural stria; lateral portion of elytra with weakly developed lateral-most series of punctures not impressed into stria; posterior margin of abdominal ventrites 2–5 bearing stout acute setae; male protibiae arcuate on inner margin; sternite VIII with median basal projection; sternite IX with wide tongue-like median portion; aedeagus 0.7 mm long; phallobase tubular, c. 1.4× longer than parameres; paremeres wide basally, narrowing from c. midlength to the quadrate apex, only slightly wider basally than apically in lateral view, completely encompassing median lobe; median lobe very narrow, reaching c. the level of apical fouth of parameres, basally reaching deeply into phallobase; gonopore subapical. Discussion. The morphology of the male genitalia and the surrounding sclerites correspond precisely to those of Group 3: American Chaetarthria defined above (compare Figs 12 A–C, F–I with Figs 2 N–S). External characters support this assignment: dorsal setae are simple and cut-off apically (compare Fig. 12 K with Fig. 2 d), elytra lack longitudinal striae except for sutural stria, and pronotum and elytra are yellowish in color. The specimens above seem to stand close to the Argentinian species C. argentina Miller, 1974 and C. hermani Miller, 1974 of the C. atra group defined by MILLER (1974). When compared with the genitalia drawings and descriptions provided by MILLER (1974) it seems that the specimens examined here represent an undescribed species. We are however leaving it undescribed, as it is likely introduced and a more detailed comparison with the American species would be necessary to diagnose the species properly. The presence of the species which is clearly an element of Neotropical fauna in Saudi Arabia is very unexpected. The first author discussed the problem with both collectors (J. Bezděk and D. Král) and with the person who mounted the specimens for NMPC (P. Pacholátko), and all of them excluded any possibility of mislabeling or mixing the Saudi Arabian material with Neotropical samples at any stage of the processing. Another alternative would be an unintended introduction of this species with some imported cargo. That could be facilitated by the fact that the species comes to light and may have been attracted to the cargo by strong lights usual in the cargo depositories and harbors. The introduction scenario is however called into question by the fact that both C. argentina and C. hermani (i.e. the species most similar to the Arabian one) live in dry areas of western Argentina (provinces of Tucumán and La Rioja) which is far from any harbor. The locality in Saudi Arabia where the specimens were collected is also quite far from the coast (c. 30 km) as well as from the nearest trade harbor (c. 100 km north). Even the introduction would hence need to be confirmed by a repeated catch., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 250-251, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["MILLER D. C. 1974: Revision of the New World Chaetarthria (Coleoptera: Hydrophilidae). Entomologica Americana 49 (1): 1 - 123."]}

Thysanarthria atriceps (Régimbart, 1903) (Figs 2a, 3B,G,H, 4 A–J) Hydrobius atriceps Régimbart, 1903: 33. Hydrobius atriceps: KNISCH (1924a: 169, catalogue); ZAITZEV (1908: 373, catalogue). Thysanarthria atriceps: ORCHYMONT (1926a: 195, transfer to Thysanarthria); ORCHYMONT (1926b: 242, transfer to Thysanarthria explained in more detail, comparison with T. championi); BALFOUR--BROWNE (1952: 134, distribution); BALFOUR- BROWNE (1957: 21, distribution); HANSEN (1999: 105, catalogue); HEBAUER (2001: 394, redescription and update of distribution); HEBAUER (2005: 39, distribution); HEBAUER (2006: 24, catalogue). Type material. Not examined. Additional material examined. MALAWI: 2 ♀♀ (NMPC): Nkhotakota env., 12.92716°S 34.2831°E, 2–3.i.2002, J. Bezděk lgt. REPUBLIC OF SOUTH AFRICA: WESTERN CAPE: 3 ♂♂, 2 unsexed specimens (NMPC): 8 km NEE of Stanford, in gravel/sand and small isolated pools at the sandy stream and on/in sandy banks along the stream, 34°25.0′S 19°32.4′E, 4–5.xii.2015, Arriaga, Fikáček, Seidel & Vondráček lgt. (RSA 49). ZIMBABWE: 1 ♂, 7 unsexed specimens (NMPC): 20 km W Gwanda, 120 km SE Bulawayo, 6.xii.1999, F. Kantner lgt. Redescription. Body length 1.4–2.0 mm, maximum body width 1.1–1.3 mm. Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with strongly granulate microsculpture on interstices; punctation sparse. Eyes separated by 2.7× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with strongly granulate microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; interval punctation sparse, setiferous; interstices without distinct microsculpture. Aedeagus (Figs 4 A–J) c. 0.5–0.6 mm long. Phallobase slightly widened at base of parameres, slightly narrower than bases of parameres combined, weakly constricted at c. midlength, slightly bent in lateral view. Paremere widely rounded basally, narrowing in apical third, apex rounded. Median lobe narrow, membranous apically, without subapical projections; apex reaching c. level of apex of parameres; gonopore transversely oval, situated in distal third. Variability. The examined specimens from the Republic of South Africa and Zimbabwe differ slightly in the shape of the basal part of the parameres (compare Figs 4 A–E and 4F – J) but seem to be identical in all other aspects including the morphology of the median lobe. Examination of much larger material from Africa covering the known distribution would be needed to reveal whether these differences may be constant and correlated with geography; without such a study we consider the observed differences to be intraspecific variation for the moment. Differential diagnosis. Thysanarthria atriceps seems to be the only species occurring in Africa and is hence easy to identify. In form of the median lobe and parameres it resembles only the Arabian T. brittoni from which it differs in relatively longer and narrower parameres and less constricted phallobase. Biology. The species seems to be usually collected at light. Examined South African specimens were collected from wet sandy banks of a small lowland stream (Fig. 11E), the beetles were found when the sandy parts were flooded with water or pressed to get submerged, which caused the beetles to float on the water surface. Distribution. Central and southern part of Africa and Madagascar (where the type locality is situated); on African continent so far recorded from Togo, the Ivory Coast, Angola, Rwanda, Burundi, Malawi, Zimbabwe, Mozambique, and the Republic of South Africa (HEBAUER 2006)., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 236-238, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["REGIMBART M. 1903: Coleopteres aquatiques (Haliplidae, Dytiscidae, Gyrinidae et Hydrophilidae) recueillis dans le Sud de Madagascar par M. Ch. Alluaud (Juillet 1900 - mai 1901). Annales de la Societe Entomologique de France 72: 1 - 51.","KNISCH A. 1924 a: Hydrophilidae. In: JUNK W. & SCHENKLING S. (eds): Coleopterorum Catalogus. Vol. 14, part 79. W. Junk, Berlin, 306 pp.","ZAITZEV F. A. 1908: Catalogue des Coleopteres aquatiques des familles Dryopidae, Georyssidae, Cyathoceridae, Heteroceridae et Hydrophilidae. Horae Societatis Entomologicae Rossicae 38: 283 - 420.","ORCHYMONT A. d' 1926 a: Note sur Thysanarthria n. g. Bulletin et Annales de la Societe Entomologique de Belgique 66: 195 - 196.","ORCHYMONT A. d' 1926 b: Contribution a l'etude des Hydrophilides VI. Bulletin et Annales de la Societe Entomologique de Belgique 66: 201 - 248.","HANSEN M. 1999: Hydrophiloidea (s. str.) (Coleoptera). World Catalogue of Insects 2: 1 - 416.","HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400.","HEBAUER F. 2005: Contribution to the knowledge of the Hydrophilidae of Malawi (Coleoptera: Hydrophilidae). Acta Coleopterologica 21 (1): 37 - 40.","HEBAUER F. 2006: Checklist of the Hydrophiloidea of Africa and adjacent archipelagos (Coleoptera: Epimetopidae, Georissidae, Helophoridae, Hydrochidae, Hydrophilidae, Spercheidae). Entomologische Zeitschrift 116: 19 - 36.","BALFOUR-BROWNE J. 1951: Coleoptera: Haliplidae, Dytiscidae, Gyrinidae, Hydraenidae, Hydrophilidae. Pp 179 - 220 + pls 10 - 11. In: Expedition to South-west Arabia 1937 - 1938. British Museum (Natural History), London, xiv + 504 pp."]}

Thysanarthria bengalensis Hebauer, 2001 (Figs 1A, 5 K–M, 11) Thysanarthria bengalensis Hebauer, 2001: 395. Type material examined. HOLOTYPE: ♂ (SMNS), ʻEAST PAKISTAN / Dinajpur / X-1969 Barbe // HOLOTYPUS / Thysanarthria / bengalensis sp.n. / des. F. Hebauerʼ. Redescription. Body length 2.2 mm, maximum body width 1.3 mm. Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with strong mesh-like microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.0× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with strong mesh-like microsculpture. Elytra with 10 striae, sharply impressed except basally; intervals distintcly convex at midlength and near apex; interval punctation sparse, setiferous; interstices with very faint mesh-like microsculpture. Aedeagus c. 0.6 mm long. Phallobase wide at base of parameres, strongly constricted at midlength into a very narrowly tubular basal part, bent in nearly right angle in lateral view close to parameral base, c. 1.3× longer than parameres. Paremeres wide, c. of same width throughout, arcuately bent, cut off apically and projecting into a small denticle apicomesally. Median lobe not examined as it is absent (damaged) in the holotype. Differential diagnosis. Thysanarthria bengalensis is the largest species of the genus and differs from all other species in all elytral series (including the mesal ones) nearly reaching the base of the elytra. In the presence of strong microsculpture on the head and pronotum it resembles T. brincki and T. saurahana, from which it can be easily distinguished by the morphology of male genitalia. The form of the phallobase (extremely constricted in dorsal/ ventral views, and bent in nearly right angle in the lateral view ‒ Fig. 5M) is also unique for this species, and makes it easy to distinguish. Biology. Unknown. Distribution. Only known from the type locality in northern Bangladesh (HEBAUER 2001)., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on page 238, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Thysanarthria siamensis Hebauer, 2001 (Figs 1C, 9 F–J, 11) Thysanarthria siamensis Hebauer, 2001: 399. Type material examined. HOLOTYPE: ♂ (NHMW), THAILAND: MAE HONG SON: ʻN-THAILAND 1993 / Mae Hong Son env. / Ban Huai Po 24-30.VI. / leg. Schneider’. Additional material examined. 1 ♂, 5 spec. (NHMW, NMPC): INDIA: UTTARKHAND: Gauri (str.), Pauri Garhwal, left tributary of River Alaknanda, ca. 2 km upstream from Thamdar, along road to Marud, ca. 8 km from Srinagar, 730 m, 11.xi.2006, lgt. M. A. Jäch; 1 ♂, 2 spec. (NHMW):River Suhma, Dehradun district, right tributary of river Ganga, ca. 5 km S Raiwala, ca. 10 km N Haridwar, 340 m, 9.ix.2006, lgt. M. A. Jäch. NEPAL: 1 ♂, 3 spec. (NHMW): Gorkha, 26.–31.v.1992, lgt. Ivo Jeniš. LAOS: VIENTIANE: 1 ♂, 2 spec. (NHMB): Laos, Vientiane, Vang-Vieng, 300, 102.4486, 18.92306, 10.v.2001 – 6.vii.2001, J. Kolibáč. THAILAND: MAE HONG SON: 1 ♂, 2 spec. (NHMW): Huai Sua Tao, 11–17.v.1992, lgt. Jan Strnad. Redescription. Body length 1.7–2.0 mm (holotype 1.8 mm), maximum body width 1.0– 1.2 mm (holotype 1.0 mm). Head and labrum black; pronotum uniformly yellowish or brown centrally and gradually getting paler towards margins; elytra uniformly yellowish to pale brown, with slightly darkened striae; legs yellowish. Head without microsculpture on interstices; punctation sparse, each puncture bearing yellowish pointed seta. Eyes separated by 3.1× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 9 F–J) 0.7 mm long. Phallobase widened in apical half, widest shortly below bases of parameres (slightly wider than parameres combined); weakly arcuate in lateral view. Parameres short, narrowly elongate, constricted at midlength, widened into rounded lobes apically; widely triangular in lateral view. Median lobe narrow, shorter than parameres, sharply pointed, without membranous apex of paired subapical lobes; gonopore circular, situated subapically. Differential diagnosis. Thysanarthria siamensis is very characteristic by a relatively large aedeagus with lanceolate parameres and sharply pointed median lobe and is hence hard to be confused with any other species of the genus. Biology. Specimens from India: Uttarkhand were collected at the sides of small to large stony rivers, microhabitat is unknown (M. A. Jäch, pers. comm.). Distribution. The species is widespread, ranging from western Himalaya to central Thailand and northern Laos., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 247-248, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Thysanarthria championi (Knisch, 1924) (Figs 2 H–M,b, 3 A,C–F, 7 A–J, 11) Chaetarthria championi Knisch, 1924b: 40. Thysanarthria championi: ORCHYMONT (1926a: 195, transfer to Thysanarthria); ORCHYMONT (1926b:242, transfer to Thysanarthria explained in more detail, comparison with T. atriceps); HANSEN (1999: 105, catalogue); HEBAUER (2001:398, redescription and update of distribution). Chaetarthriomorphus sulcatus Chiesa, 1967: 276, syn. nov. Thysanarthria sulcata: HANSEN (1991: 126, transfer to Thysanarthria); HANSEN (1999: 105, catalogue).All other records of this species refer to different species, see under T. persica sp. nov. and T. wadicola sp. nov. Type material examined. Chaetarthria championi. LECTOTYPE (here designated): ♂ (BMNH), INDIA: UTTARKHAND: ʻRanikhet / Kumaon / India, H. G. C. // G. C. Champion / Brit. Mus. / 1924-42. // Chaetarthria / championi / Knisch // det. Knisch / W. E. Z. 1924ʼ. PARALECTOTYPES: 1 spec. (BMNH), same label data as the lectotype; 1 spec. (BMNH): ʻW. Almora / Kumaon U.P. / India, H. G. C. // G. C. Champion / Brit. Mus. / 1924-42. // Chaetarthria / championi / Knisch // Knisch det. 1922 / Chaetarthria / championiʼ; 1 spec. (BMNH): ʻW. Almora / Kumaon / India, H. G. C. // G. C. Champion / Brit. Mus. / 1924-42. // Chaetarthria / championi / Knisch // Knisch det. 1922 / Chaetarthria / championiʼ Chaetarthriomorphus sulcatus: LECTOTYPE (here designated): ♂ (HNHM): AFGHANISTAN: ʻNO.Afghan.1953 / J. Klapperich // Nuristan, 1200 m / Bashgultal, 20.IV. // Paratypus 1964 / Chaetarthriomorphus / sulcatus / Chiesa // CHAETARTHRIOMORPHUS / sulcatus / CHIESA / CHIESA DET. // AEDEAGUS / DRAWN BY / P. D. PERKINS’. Additional material examined. NEPAL: 1 ♂ (NMPC), S Ganesh Himal village,near Kali Sundhara Bazar, 700 m, 24.–25.v.1996,lgt.Ahrens, Kulbe & Rulik; 1 ♂, 3 specimens (SMNS): Narayani, Sauraha, bank of Rapti River, light trap, 180, 84.49695, 27.56667, 2000-04-18, A. Weigel; 1 ♂ (SMNS):same label data but lgt.A. Skale. INDIA: UTTARANCHAL: 1 ♂, 22 specimens (NMPC): ca. 13 km NW of Nainital, Khaira [= Khairna] bridge, near river, at light, 900 m, 13.–17.vii.2003, lgt. Z. Kejval & M. Trýzna. ARUNACHAL PRADESH: 1 ♂, 8 specimens (NMPC): 8 km S Jamiri-Sesa vicinity, 350 m, 4.–26.v.2006, lgt. P.Pacholatko. CHINA: YUNNAN: 1 ♂, 2 spec. (NHMW): 100 km W of Kunming, Diaolin Nature Reserve, 22.v.–2. vi.1993, lgt.E. Jendek & O.Šauša; 1♂, 2 spec. (NMPC):Tongbiguan vill., near river, at light, 1340 m, 24°36.7ʹN 97°39.4ʹE, 24.–26.vi.2018, lgt. J. Hájek &J.Růžička. MYANMAR: 1♂, 6 specimens (NHMW): Mandalay, ca. 50 km NW Kalaw,Myitsona river, 450 m, 25.x.1998,lgt.Schillhammer. Redescription. Body length 1.5–2.0 mm (holotype 1.9 mm), maximum body width 1.0– 1.1 mm (holotype 1.0 mm). Head and labrum black; pronotum yellowish with vaguely delimited darker central spot of variable extent or in some specimens (incl. holotype) completely dark brown; elytra yellowish with darkened elytral striae, or with darker lateral parts, or uniformly brown (incl. in holotype); legs yellowish to brown. Head with weak microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.1× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible (but darker spots may be present, resembling real punctures); intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 7 A–J) c. 0.5 mm long. Phallobase not much wider at base of parameres than more basally, only indistinctly narrowed at midlength; arcuate in lateral view. Paremere wide basally, gradually narrowing towards apex, outer face nearly continuously arcuate, slightly bisinuate in apical fourth, apex bluntly pointed; mesal face with short cuticular asperities (visible in cleaned aedeagus only, Fig. 7E). Median lobe widely bottle-shaped, without paired subapical projections; apex nearly reaching level of parameral apices, membranous, rounded in relaxed position (Figs 7D, I–J), with a pair of backwards directed lobes when fully everted (not usually visible); gonopore rounded, situated subapically. Differential diagnosis. Thysanarthria championi resembles T. bifida sp. nov., T. trifida sp. nov., and T. chui sp. nov. in the general morphology of the aedeagus and the basally wide parameres arcuately narrowing into widely to narrowly rounded apex; of these T. bifida and T. trifida can be distinguished by the presence of a pair of subapical projections on the median lobe (absent in T. championi); T. chui lacks these lobes, but its parameres are relatively shorter and more abruptly narrowed apically, projecting into rounded lobes. Thysanarthria championi is one of four species co-occurring in Himalaya, along with T. madurensis, T. saurahana sp. nov., and T. siamensis; it can be easily distinguished from all of them by the morphology of male genitalia. Comments on synonymy. The above type specimen of Chaetarthriomorphus sulcatus is the only found in the Klapperich collection in HNHM. It is largely damaged, with prothorax and one elytron completely missing. However, the abdomen and male genitalia are present, and the morphology of the aedeagus corresponds completely with that of the lectotype of T. championi. The elytron is paler, not dark brown, which further supports the fact that C. sulcatus cannot be conspecific with the specimens from southern Iran (described here as T. persica sp. nov.) and the northern Arabian Peninsula (described here as T. wadicola sp. nov.) as erroneously reported by HEBAUER (1997) and FIKÁČEK et al. (2010). Following these facts, the examined specimen is designated as the lectotype, and Chaetarthriomorphus sulcatus is here placed in synonymy with Chaetarthria championi. Biology. Part of the examined specimens was collected at light on river banks, no more information is available. Distribution. The species is widely distributed in the foothills of the Himalaya Mts. and the adjacent mountain systems in eastern Afghanistan (Hindukush Mts.), southwestern China (Yunnan), and Myanmar. The specimens listed by HEBAUER (2001) from Laos are females and hence their identity cannot be confirmed., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 242-243, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["KNISCH A. 1924 a: Hydrophilidae. In: JUNK W. & SCHENKLING S. (eds): Coleopterorum Catalogus. Vol. 14, part 79. W. Junk, Berlin, 306 pp.","KNISCH A. 1924 b: Neue palpicornier aus dem sudlichen Himalaya (Col. Hydrophilidae - Op. 15). Wiener Entomologische Zeitung 41: 29 - 41.","ORCHYMONT A. d' 1926 a: Note sur Thysanarthria n. g. Bulletin et Annales de la Societe Entomologique de Belgique 66: 195 - 196.","ORCHYMONT A. d' 1926 b: Contribution a l'etude des Hydrophilides VI. Bulletin et Annales de la Societe Entomologique de Belgique 66: 201 - 248.","HANSEN M. 1999: Hydrophiloidea (s. str.) (Coleoptera). World Catalogue of Insects 2: 1 - 416.","HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400.","CHIESA A. 1967: Compimento di una revisione di Hydrophilidae del Afghanistan (Coleoptera: Hydrophilidae). Annales Historico-Naturales Musei Nationalis Hungarici 59: 275 - 277.","HANSEN M. 1991: The hydrophiloid beetles. Phylogeny, classification and a revision of the genera (Coleoptera, Hydrophiloidea). Biologiske Skrifter 40: 1 - 368.","HEBAUER F. 1997: Annotated checklist of the Hydrophilidae and Helophoridae (Insecta: Coleoptera) of the Arabian Peninsula with a description of a new genus and species. Fauna of Saudi Arabia 16: 255 - 276.","FIKACEK M., GENTILI E. & SHORT A. E. Z. 2010: Order Coleoptera, family Hydrophilidae. Pp. 135 - 165. In: HARTEN A. VAN (ed.): Arthropod Fauna of the United Arab Emirates. Volume 3. Al Ummah Printing, Publishing, Distribution and Advertising, Abu Dhabi, 700 pp."]}

Thysanarthria Orchymont, 1926 Thysanarthria Orchymont, 1926a:195. Type species: Hydrobius atriceps Régimbart, 1903 by original designation. = Chaetarthriomorphus Chiesa, 1967: 276. Type species: C. sulcatus Chiesa, 1967 by monotypy. Synonymized by HANSEN (1991: 126). Diagnosis. The genus can be recognized from other co-occurring genera of the Hydrophilidae based on the following combination of characters: body small to medium sized (1.4–2.2 mm); head black, pronotum and elytra yellowish to pale brown in most species, uniformly brown in the remaining ones (Figs 1 A–D); head with large exposed well sclerotized labrum (e.g., Fig. 1B); antenna with 9 antennomeres, scape very long, pedicel bulbose, antennomeres 3–5 very small, cupule and three-segment antennal club pubescent (Fig. 3D); maxillary palpomere 4 basally with row of many peg-like setae (Fig. 3E); mentum projecting anteromedially, with row of setae along anterior margin (Fig. 3A); gular sutures contiguous (Fig. 3C); mesoventrite distinctly divided from anepisterna by sutures, sutures widely separated on anterior margin of mesothorax (Fig. 3B); mesoventrite flat except of small semicircular elevation posteromesally (Fig. 3B); metaventrite short, sparsely pubescent only mesally and anterolaterally (Fig. 3B); elytra with 10 sharply impressed striae (Figs 1 A–D); whole dorsal surface covered by sparsely arranged setae which are trifid basally with a long median projection (Figs 1C, 2 a–b); profemora pubescent in basal half (Fig. 3C); mesofemora pubescent anterobasally (Fig. 3B); metafemora bare except on anterobasal margins (Fig. 3B); tarsi rather short and stout, metatarsus with all tarsomeres c. equal in length (Fig. 3F); abdomen with 5 ventrites, basal two bearing shallow cavity covered by long setae arising from base of ventrite 1, holding whitish gelatinous substance (Figs 3 G–H); ventrite 1–2 with median carina; male abdominal sternite 8 with narrow median projection (Fig. 2H); male sternite 9 V-shaped medially (Fig. 2J); aedeagus with long tubular phallobase, base of median lobe not reaching deeply into phallobase (Figs 4–9). Differential diagnosis. The base of abdomen with series of long setae covering a gelatinous substance and antenna with bulbous pedicel distinguish Thysanarthria from all other non-chaetarthriine genera. Within Chaetarthriini, the well sclerotized and widely exposed labrum differentiates it from Hemisphaera Pandellé, 1876 (which is also smaller and has more depressed body: see FIKÁČEK et al. 2012, JIA et al. 2013) which can co-occur with Thysanarthria, and from the Neotropical genus Guyanobius Spangler, 1986 (see GUSTAFSON & SHORT 2010). Thysanarthria can be distinguished from all three groups of Chaetarthria defined above by the elytra with 10 sharply impressed striae (Figs 1 A–D). Most species of the genus are easy to recognize in the samples by their small body size and pale coloration of pronotum and elytra constrasting with the black head (this coloration is not present only in the Near East T. persica sp. nov. and T. wadicola sp. nov.). Characters important for species-level identification. All known species of Thysanarthria are very similar to each other in most external characters, and their tiny size makes the observation of many characters very difficult. The only external characters are (1) the presence/absence of the microsculpture on the head and labrum, pronotum and elytra, which can be either strongly mesh-like, weak and granulate, or totally absent; and (2) the body shape which can be wider (Fig. 1A) or more elongate (Figs 1B, D), but this is hard to compare in specimens which are not mounted in extended position on labels. Body coloration differs between species, with pronotum and elytra either uniformly yellowish (Figs 1A, C) or partly darkened (e.g. pronotum in Fig. 1D) or uniformly dark brown (Fig. 1B). However, examination of longer series of some species (T. championi and T. siamensis) revealed that the coloration can vary within a species, and hence is not always reliable for identification. The same is true for the dorsal body microsculpture which seems to vary in intensity, at least in T. brittoni (see under that species). The body size also differs between species, and the presence of specimens of different size in the same series may indicate the presence of multiple species. However, in species in which more specimens were available, the body size was revealed to vary to some extent as well, and the body size can be hence used as an additional character only. Therefore, examination of the male genitalia is necessary for reliable identification in all cases. Ideally, the genitalia should be examined under a medium magnification of the compound microscope, and attention should be paid also to the membranous structures on the apical part of the median lobe (including short, paired, subapical projections which are present only in some species, e.g. Figs 5 D–E, I–J, 6 D–E, I–J). The proportions of parameres may be uneasy to observe as they are partly affected by the position of the aedeagus, and the genitalia should be carefully observed under slightly different angles in case of doubts. The ratio of paramere length to phallobase length should be evaluated in lateral view, due to the strongly bent phallobase in many species. The examination of the material used for this study shows that especially the form of the median lobe is constant and diagnostic, whereas the shape of parameres may slightly vary. The apex of the median lobe is membranous in many species, even though usually rather constant in shape, and it seems that at least in some species it can include parts which are normally inverted and hence not easy to observe, and may sometimes get fully everted after the treatment in KOH (which however may distort other parts of the aedeagus; see e.g. 4J and 7E which show fully everted apical membranous parts). Since the observation of this part is difficult, we did not consider it for species diagnosis. As male genitalia are the only reliable character for species identification, below we provide detailed illustrations of the genitalia with which new specimens to be identified should be compared. Once the candidate species is found based on genital morphology, the external characters mentioned above (body size and coloration, presence/ absence of the microsculpture) should be compared with the (re)descriptions provided below. No identification key is hence provided. Species groups. The limited number of characters makes it difficult to group the species into supposedly monophyletic species groups. Based on the genital morphology, the African Thysanarthria atriceps is very similar to the Arabian T. brittoni, and these two species seem to form a group of closely related species. The presence of subapical membranous lobes on the median lobe in T. brincki, T. bifida, T. cardamona, T. madurensis, and T. trifida (Figs 5 D–E, I–J; 6 D–E, I–J; 8 N–O) may also point to a close relationships. Thysanarthria brincki and T. cardamona may form a clade within this group characterized by lateroapical spine on the paramere (Figs 5 A–J). Function of the abdominal gelatinous substance. All members of the tribe Chaetarthriini including Thysanarthria bear a series of long setae on the base of the abdomen which cover a shallow depression in ventrites 1–2 filled in by whitish gelatinous substance (Figs 3 G–H). When submerged, Thysanarthria floats with dorsal body surface facing up, i.e. in the position usual for most other Hydrophilidae. The gelatinous substance hence does not serve to increase the buoyancy of the beetle as might be the case in the non-related genus Amphiops Erichson, 1843 which bears similar-looking gelatinous substance at the base of abdomen and is swimming in an upside-down position when submerged (Fikáček & Angus, pers. observ.). Moreover, the gelatinous substance does not interfere with the ventral air bubble of the submerged beetle: the bubble covers the whole ventral side of the beetle including the whole abdomen. Therefore, it seems that the substance cannot be functional in submerged beetle but may be an adaptation to its usual environment on the wet sand outside water. The gelatinous substance is sticky in alive specimens. Its function remains unknown., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 234-236, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["ORCHYMONT A. d' 1926 a: Note sur Thysanarthria n. g. Bulletin et Annales de la Societe Entomologique de Belgique 66: 195 - 196.","REGIMBART M. 1903: Coleopteres aquatiques (Haliplidae, Dytiscidae, Gyrinidae et Hydrophilidae) recueillis dans le Sud de Madagascar par M. Ch. Alluaud (Juillet 1900 - mai 1901). Annales de la Societe Entomologique de France 72: 1 - 51.","CHIESA A. 1967: Compimento di una revisione di Hydrophilidae del Afghanistan (Coleoptera: Hydrophilidae). Annales Historico-Naturales Musei Nationalis Hungarici 59: 275 - 277.","HANSEN M. 1991: The hydrophiloid beetles. Phylogeny, classification and a revision of the genera (Coleoptera, Hydrophiloidea). Biologiske Skrifter 40: 1 - 368.","FIKACEK M., DELGADO J. A. & GENTILI E. 2012: The hydrophiloid beetles of Socotra Island (Coleoptera: Georissidae, Hydrophilidae). Acta Entomologica Musei Nationalis Pragae 52 (supplementum): 107 - 130.","JIA F., FIKACEK M. & SONG K. 2013: Hemisphaera orientalis new species, the first species of Hemisphaera from the Oriental Region (Coleoptera: Hydrophilidae: Chaetarthriini). Journal of the Kansas Entomological Society 86: 301 - 306.","SPANGLER P. J. 1986: Three new species of water scavenger beetles of the genus Chaetarthria from South America (Coleoptera: Hydrophilidae). Proceedings of the Biological Society of Washington 99: 509 - 516.","GUSTAFSON G. T. & SHORT A. E. Z. 2010: Revision of the Neotropical water scavenger beetle genus Guyanobius Spangler, 1986 (Coleoptera: Hydrophilidae: Chaetarthriini). Aquatic Insects 32: 245 - 258.","KNISCH A. 1924 a: Hydrophilidae. In: JUNK W. & SCHENKLING S. (eds): Coleopterorum Catalogus. Vol. 14, part 79. W. Junk, Berlin, 306 pp."]}

Thysanarthria ceylonensis Hebauer, 2001 (Figs 6 K–O, 11) Thysanarthria ceylonensis Hebauer, 2001: 396 Type material examined. HOLOTYPE: ♂ (MZLU), SRI LANKA: NORTHERN PROVINCE: ʻCeylon, N. Prov. / Kudattanai / 6 mls SE Point Pedro / 13.II.62, Loc. 70 // At pond in semi- / desert // Lund University / Ceylon Expedition 1962 / Brinck-Andersson- / Cederholm // MZLU / Type no. / 3120:1 // Photo 2017 / by MZLU // MZLU / 2017 / 511’. Additional material examined. INDIA: MADHYA PRADESH: 1 ♂, 2 specimens (NHMW, NMPC): River Denwa, ca. 8 km SSE Matkuli, Satpura Range, 400 m, 28.ii.2008, lgt. M. Jäch, S. & P. Sharma; 1 ♀ (NHMW): Hoshangabad Distr., Bandrabhan, ca. 60 km SSE Bhopal, ca. 5 km NE Hoshangabad, River Narmada, 280 m, 23.‒24.ii.2008, lgt. M. Jäch, S. & P. Sharma; 1 spec. (NHWM): Chhindwara Distr., Bhadhua Chora (stream), ca. 10 km E Matkuli near Mahul Jhir, 400 m, 28.ii.2008, lgt. M. Jäch, S. & P.Sharma; 1♀ (NHMW): Hoshangabad Distr., Dhobighat Nala (stream), ca. 2 km SE Pachmarhi,Saphura Range, 900 m, 27.ii.2008, lgt. M. Jäch, S. & P. Sharma. Redescription. Body length 1.5–1.7 mm (holotype 1.5 mm), maximum body width 0.9–1.0 mm (holotype 0.9 mm). Head and labrum black and pronotum uniformly yellowish; elytra yellowish with slightly darker lateral parts; legs reddish to yellowish. Head with strong microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.5× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 6 K–O) 0.4 mm long. Phallobase not much wider at base of parameres than more basally, only indistinctly narrowed at midlength; arcuate in lateral view. Paremere moderately wide basally, slightly narrowing towards apex, apex widely angulate. Median lobe widely bottle-shaped, rounded apically, without paired subapical projections; apex not reaching level of parameral apices; gonopore rounded, situated far from apex. Differential diagnosis. Thysanarthria ceylonensis resembles T. bengalensis, T. brincki and H. saurahana in having strong mesh-like microsculpture on the head, but it can be easily distinguished from all these species as well as from all other Thysanarthria by a very characteristic aedeagus. Biology. Specimens from Madhya Pradesh were collected at the sides of small to large rivers with stony banks (e.g., Fig. 11D) but precise microhabitat is not known (M. A. Jäch, pers. comm.). Distribution. Described from Sri Lanka (HEBAUER 2001) but here recorded from central India (Madhya Pradesh), hence the species is likely widespread in the Indian Peninsula., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 240-242, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400."]}

Thysanarthria persica sp. nov. (Figs 1B, 10 A–E, 11) Thysanarthria cf. sulcata (part): FIKÁČEK et al. (2010: 139; misidentification). Type material. HOLOTYPE: ♂ (NMPC), IRAN: SISTAN AND BALUCHESTAN: Iran, Baluchistan, 16 km SE of Tange-Sarhe, 61 km, NNW of Nik-shahr, 10.iv.1973, Expedition National Museum Prague,locality 154. PARATYPES: 4 spec. (NMPC), same data as the holotype. FARS: 1 ♂ (NMPC): Iran, Fars,Ali-abad, 75 km NW of Djahrom,wadi of the river Shur, 10.vii.1970, Expedition National Museum Praha,locality 53. KERMAN: 1 ♂ (NHMW): Iran, Kerman, Manujan, 110 km E Bandarabaas, at light, 2.vi.1974, lgt. Pretzmann, Exp. Nat. Hist. Mus. Vindob. [= expedition of the Natural History Museum, Vienna]. Description. Body length 1.7–1.9 mm (holotype 1.7 mm), maximum body width 1.0– 1.1 mm (holotype 1.0 mm). Head and labrum black; pronotum dark brown in centre, becoming slightly paler towards margins; elytra uniformly dark brown; legs brown. Head without microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 2.5× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except in basal fourth where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 10 A–E) 0.5 mm long. Phallobase slightly widened at base of parameres, c. as wide as parameres combined, slightly narrowing towards base, arcuately bent in lateral view. Parameres narrowly elongate, gradually narrowing towards apex, outer face arcuate or indistinctly sinuate. Median lobe narrow with widely rounded membranous apex nearly reaching level of parameral apices, paired subapical projections absent; gonopore transversely oval, situated in distal fourth of median lobe. Differential diagnosis. Unlike most other Thysanarthria except T. wadicola sp. nov., T. persica has uniformly dark pronotum and elytra. Its genitalia are characteristic by rather elongate parameres with arcuate lateral face and widely rounded apex (in contrast to T. wadicola with prolonged acuminate apices of parameres). It also differs from T. wadicola in the median lobe nearly reaching the level of apices of parameres (in contrast to very short median lobe in T. wadicola), in parameres c. one third as long as phallobase when seen in lateral view (c. as long as phallobase in T. wadicola) and in moderately wide bases of parameres in lateral view (very wide base narrowing into a very narrow apex in lateral view in T. wadicola). Etymology. The name refers to Persia, the historical name of Iran this new species is described from. Adjective. Biology. Based on HOBERLANDT (1981), the type locality was a rocky bank of a mountain torrent without vegetation at c. 900 m of altitude on stony mountains slopes; the specimens were collected from small gravel strands on the bank of the brook. The paratype from Fars was collected in a wadi with a stream with muddy and sandy banks (HOBERLANDT 1974). Distribution. So far only known from southern Iran., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on page 246, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["FIKACEK M., GENTILI E. & SHORT A. E. Z. 2010: Order Coleoptera, family Hydrophilidae. Pp. 135 - 165. In: HARTEN A. VAN (ed.): Arthropod Fauna of the United Arab Emirates. Volume 3. Al Ummah Printing, Publishing, Distribution and Advertising, Abu Dhabi, 700 pp.","HOBERLANDT L. 1981: Results of the Czechoslovak-Iranian entomological expeditions to Iran. Introduction to the Second expedition 1973. Acta Entomologica Musei Nationalis Pragae 40: 5 - 32 + photos 1 - 42.","HOBERLANDT L. 1974: Results of the Czechoslovak-Iranian entomological expedition to Iran 1970. Np. 1: Introduction. Acta Entomologica Musei Nationalis Pragae, Supplementum 6: 9 - 20 + Figs 1 - 22."]}

Thysanarthria wadicola sp. nov. (Figs 10 F–J, 11) Thysanarthria sulcata (misidentification): HEBAUER (1997: 267; records from Oman, illustration of genitalia); HEBAUER (2001:399, taxonomic revision). Thysanarthria cf. sulcata (part): FIKÁČEK et al. (2010: 139; misidentification). Thysanarthria sp. (SLE127): SHORT & FIKÁČEK (2013; molecular phylogeny). Thysanarthria wadicola: RIBERA et al. (2019: 264; review of Oman aquatic beetles). Type material. HOLOTYPE: ♂ (NMPC): OMAN: Wadi Andam, 20 km N Samad, 650 m, 17.–18.iv.1985, lgt. C. Holzschuh. PARATYPES: 2 ♂♂ (SMNS): same data as the holotype; 3 spec. (IBEB): Murri env., wadi Bani Ghafir, 759 m, stream with pools, 23º29′46.2″N 56º53′34.8″E, 7.iv.2010, Ribera & Cieslak lgt.; 1 spec. (IBEB): Said Bin Sahran env., wadi Indam, Rd. 33, 463 m, residual pools, 22º45′15.2″N 58º00′56.9″E, 8.iv.2010, Ribera & Cieslak lgt. Additional material examined. UNITED ARAB EMIRATES: 1 ♀ (NMPC): Hatta, at light, 8.–26.iv.2006, lgt, A. van Harten. This female specimen was collected very close to the type locality of the species and externally corresponds well with the Oman specimen, we hence consider it conspecific. As no male is available from the locality, We are however not including it into the type series. Redescription. Body length 1.6–1.7 mm (holotype 1.6 mm), maximum body width 0.9–1.0 mm (holotype 0.9 mm). Head and labrum black; pronotum uniformly dark brown; elytra uniformly dark brown; legs brown. Head without microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.3× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (around scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus (Figs 10 F–J) 0.4 mm long. Phallobase slightly widened at bases of parameres, slightly narrower than parameres combined, weakly narrowing more basally in ventral/dorsal view, in lateral view phallobase c. as long as parameres, arcuate, and strongly constricted subbasally. Parameres wide basally, continually narrowing into prolonged pointed apex, outer face slightly sinuate, in lateral view very wide basally and very narrow apically. Median lobe very short, less than half the length of parameres, without distinct membranous part on the apex, without paired projections, gonopore circular, situated apically. Differential diagnosis. Thysanarthria wadicola differs from most species of the genus except T. persica in uniformly dark brown pronotum and elytra. For differences from T. persica see under that species. Etymology. The species name is a combination of wadi (an Arabic word for seasonally dried-up riverbed) and the suffix -cola derived from the word incola (Latin, = inhabitant). Noun in apposition. Biology. Part of the specimens was collected at margins of small rocky pools at the side of a drying-up stream (see RIBERA et al. 2019: Figs 7–8). Distribution. The species is so far known only from few closely situated localities on the northeastern tip of the Arabian Peninsula., Published as part of Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), pp. 229-252 in Acta Entomologica Musei Nationalis Pragae 59 (1) on pages 248-250, DOI: 10.2478/aemnp-2019-0020, http://zenodo.org/record/4488918, {"references":["HEBAUER F. 1997: Annotated checklist of the Hydrophilidae and Helophoridae (Insecta: Coleoptera) of the Arabian Peninsula with a description of a new genus and species. Fauna of Saudi Arabia 16: 255 - 276.","HEBAUER F. 2001: The species of the genus Thysanarthria d'Orchymont, 1926 (Coleoptera: Hydrophilidae). Beitrage zur Entomologie 51: 393 - 400.","FIKACEK M., GENTILI E. & SHORT A. E. Z. 2010: Order Coleoptera, family Hydrophilidae. Pp. 135 - 165. In: HARTEN A. VAN (ed.): Arthropod Fauna of the United Arab Emirates. Volume 3. Al Ummah Printing, Publishing, Distribution and Advertising, Abu Dhabi, 700 pp.","SHORT A. E. Z. & FIKACEK M. 2013: Molecular phylogeny, evolution and classification of the Hydrophilidae (Coleoptera). Systematic Entomology 38: 723 - 752.","RIBERA I., HERNANDO C. & CIESLAK A. 2019: Aquatic Coleoptera of North Oman, with description of new species of Hydraenidae and Hydrophilidae. Acta Entomologica Musei Nationalis Pragae 59: 253 - 272."]}