A review of Microdytes J. Balfour-Browne, 1946 from Thailand, Laos, and Cambodia with descriptions of five new species and new records (Coleoptera, Dytiscidae) Author Okada, Ryohei https://orcid.org/0000-0002-8488-0660 Thailand Natural History Museum, National Science Museum, Technopolis, Pathum Thani, Thailand & Coleopterological Society of Japan, National Museum of Nature and Science, Tsukuba, Japan wasserinsekt@kub.biglobe.ne.jp Author Jaitrong, Weeyawat https://orcid.org/0000-0003-1362-0754 Thailand Natural History Museum, National Science Museum, Technopolis, Pathum Thani, Thailand Author Wewalka, Guenther https://orcid.org/0000-0002-2994-8001 Starkfriedgasse 16 / 1 / 3, A - 1190 Vienna, Austria text ZooKeys 2023 2023-04-25 1159 87 119 http://dx.doi.org/10.3897/zookeys.1159.99218 journal article http://dx.doi.org/10.3897/zookeys.1159.99218 1313-2970-1159-87 CD97DD120549412F976508D8DE21605B ECCECB868071523DB7628E304850BD62 Microdytes ubonensis Okada & Wewalka sp. nov. Figs 6 , 11 , 16 , 40A Type locality. Thailand, Ubon Ratchathani Province, Si Mueang Mai Dist., Nam Thaeng, 15°32'19"N , 105°24'08"E , alt. 200 m. Type material. Holotype (THNHM): ♂, "THAI: Ubon Ratchathani Si Mueang Mai Dist., Nam Thaeng St. 242 (alt. 200 m) 23.V.2021 R. Okada leg." [printed white label] / HOLOTYPE Microdytes ubonensis sp. nov. Okada & Wewalka 2022" [printed red label]. Paratypes (52 exs.): 3♂♂, 1♀, with same data as the holotype (CGW, CRO); 4♀♀, Thailand, Ubon Ratchatani Province, Nam Yuen Dist., Dom Pradit St. 221 (alt. 190 m), 14.402°N , 104.215°E , 26.II.2021 R Okada leg. (THNHM); 4♂♂, 4♀♀, Thailand, Ubon Ratchathani Province, Nam Yuen District, Dom Pradit St. 240 (alt. 260 m), 14°23'22"N , 105°09'25"E , 22.V.2021, R. Okada leg. (CRO); 18 exs., Laos, Savannakhet Province, Phou Xang He NBCA, ca. 5 km SW Ban Pa Phaknau, 17°00'N , 105°38'E , alt. 250-400 m, 31.V.-6.VI. 2011, NHMB Basel, Laos 2011 Expedition, M. Brancucci, M. Geiser, D. Hauk, Z. Kraus, A. Phantala & E. Vongphachan leg. (CGW, NMB, NMP); 1♂, Laos, Champasak Province, Bolavens Plateau, waterfall ca. 2 km E Tad Katamtok, 15°08.1'N , 106°38.8'E , alt. 415 m, 10.-12.V.2010, J. Hajek leg. (NMP); 15 exs., Laos, Champasak Province, Bolavens Plateau, ca. 1 km S Ban Lak 40 [vill.] Tad Yueang waterfall, 15°10.8'N , 106°08.3'E , alt. 900-970 m, 28.IV.2010, J. Hajek leg. (CGW, CRO, NMP); 1♂, Laos, Vientiane Province, Phou Khao Khouay NBCA ca. 46 km N Vientiane (waterfall), 18°22.4'N , 102°42.4'E , alt. 270 m, 18.V.2010, J. Hajek leg. (NMP); 1♀, Laos, Vientiane Province, 90 km E Vientiane, Phou Khao Khouay NP, Nam Leuk, 1.-8.VI.1996, H. Schillhammer leg (NMW). All paratypes are provided with printed red paratype labels. Diagnosis. Microdytes ubonensis sp. nov. is similar to M. boukali Wewalka, 1997 and M. lotteae Wewalka, 1998 in habitus, size, and pronotal coloration but differs from these species by having yellowish head and the elytral markings with distinct post-median spot near suture and finely and sparsely punctured ventral surface. M. ubonensis sp. nov. also resembles M. huangyongensis Bian et al., 2015 in habitus and coloration but it differs in size and male genitalia. Description. Measurements . TL = 1.25-1.40 mm (1.37 mm), TL-h = 1.08-1.19 mm (1.18 mm), MW = 0.87-0.95 mm (0.95 mm), TL/MW = 1.42-1.47 (1.44). Body regularly oval, moderately convex (Fig. 6 ). Coloration . Head yellowish brown. Pronotum dark brown, indistinctly yellowish brown at lateral sides. Elytron dark brown with yellowish brown markings forming a distinct transverse band at base not reaching suture, with a post-median lateral spot and a triangular spot near apex and often with a distinct longitudinal post-median spot near suture (Figs 6 , 11 ). Ventral surface of head and prothorax yellowish brown; thorax, abdominal ventrites and elytral epipleuron reddish brown to dark brown. Legs, antennae and palpi yellowish brown. Sculpture and structure . Head finely, sparsely, and relatively regularly punctured; almost entirely microreticulate; clypeus not bordered (Fig. 40A ). Pronotum quite regularly, sparsely, and fairly strongly punctured, coarser punctures along the posterior margin; without microreticulation; lateral margins very finely bordered, regularly rounded. Elytron moderately regularly and densely punctured, progressively finer and sparser towards lateral margin; longitudinal rows of stronger punctures not distinct; highly polished and shining; without microreticulation. Ventral surface: metacoxae and metasternum finely and sparsely punctured, abdomen without punctures; without microreticulation. Male. Median lobe of aedeagus in ventral aspect equally tapered from base to apex, with a small swelling at apex (Fig. 16A ); in lateral aspect tapered from base to apex, with a small ventral hook at apex (Fig. 16B ). Paramere narrow triangular in lateral aspect (Fig. 16C, D ). Figure 17. Microdytes balkei A median lobe in ventral aspect B median lobe in lateral aspect C left paramere in lateral aspect D right paramere in medial aspect. Scale bar: 0.25 mm. Female. Without secondary sexual characters. Sclerotized spermatheca not found. Variation. Variation of markings is shown in Fig. 11 . Etymology. This species is named after the popular provincial name of the type locality. Habitat. This species was collected in a variety of habitats. At the type locality, specimens were collected from a small stream on a more or less deforested bedrock (Fig. 48 ). At other localities, specimens were collected in small pit holes near small forest streams with rich leaf deposits. Distribution. Thailand: Ubon Ratchathani Province; Laos: Savannakhet, Champasak, and Vientiane provinces.