Research Article |
Corresponding author: Ryohei Okada ( wasserinsekt@kub.biglobe.ne.jp ) Academic editor: Mariano Michat
© 2023 Ryohei Okada, Weeyawat Jaitrong, Günther Wewalka.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Okada R, Jaitrong W, Wewalka G (2023) A review of Microdytes J. Balfour-Browne, 1946 from Thailand, Laos, and Cambodia with descriptions of five new species and new records (Coleoptera, Dytiscidae). ZooKeys 1159: 87-119. https://doi.org/10.3897/zookeys.1159.99218
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The diving beetle genus Microdytes J. Balfour-Browne, 1946 in Thailand, Laos, and Cambodia is reviewed, and five new species are described: Microdytes eliasi Wewalka & Okada, sp. nov. (Thailand, Cambodia), M. jeenthongi Okada & Wewalka, sp. nov. (Thailand), M. maximiliani Wewalka & Okada, sp. nov. (Laos, China), M. sekaensis Okada & Wewalka, sp. nov. (Thailand, Laos), M. ubonensis Okada & Wewalka, sp. nov. (Thailand, Laos). Two species are the first country records: M. balkei Wewalka, 1997 (Laos, Cambodia) and M. wewalkai Bian & Ji, 2009 (Laos). For 12 and 8 species, the first provincial records from Thailand and Laos, respectively, are given. A checklist, a key to the 25 known Microdytes species from these countries, and habitus images and illustrations of diagnostic characters are provided. Distribution maps of the recorded species are presented, and species distribution patterns are also briefly discussed.
Diving beetles, faunistics, key to species, Southeast Asia, taxonomy, zoogeography
The dytiscid genus Microdytes J. Balfour-Browne, 1946 contains 47 described species classified in the tribe Hyphydrini of the subfamily Hydroporinae (
During 2018–2022, as part of the field survey by the senior author to reveal diversity of Thailand diving beetles, a total of 228 Microdytes specimens were collected from 30 localities. For comparative purposes, we also studied specimens from Thailand, Laos, and Cambodia, mainly collected as part of the “NHMB Basel, Laos Expeditions” in 2011 and 2012 (
In this paper, we describe five new species from Thailand, Laos, and Cambodia, increasing the number of known Microdytes species to 52. New and first regional records from those countries are also given. A checklist and a key to all Microdytes species known from these countries are provided. To facilitate the identification of the species, photographs of habitus and discriminant characters are provided for the first time. Distribution maps of the recorded Microdytes species are also presented, and their distribution patterns and microhabitat preferences are briefly discussed.
The study was based on the examination of 695 specimens: 241 from Thailand, 420 from Laos, and 34 from Cambodia. These specimens are deposited in the following institutions and private collections:
CGW Collection Günther Wewalka, Vienna, Austria;
CRO Collection Ryohei Okada, Tokyo, Japan;
THNHM Thailand Natural History Museum, Pathum Thani, Thailand.
Beetles were pin mounted on square or triangular card points. Male genitalia were dissected, then put on cards for detailed observation. The holotypes, paratypes, and lectotype of the closely related species were examined. Specimens from Myanmar were also used for comparisons.
The beetles were studied with an Olympus SZX10 compound microscope equipped with Nomarsky optics up to 1000×. Habitus photographs were taken using a Canon EOS 7D Mark II digital camera with attached Canon MP-E65 mm f/2.8 macro lens with 5:1 optics. Male genitalia were illustrated wet, using an Olympus BHT transmitted light microscope with a RICOH GX6 attachment. Composite images were created using the image stacking software Helicon Focus (Helicon Soft Ltd., Kharkov), and subsequently edited with Adobe Photoshop elements (2008) (Adobe Systems Inc., USA) where necessary.
The terminology to denote the orientation of the genitalia follows
Body measurements were made with a compound microscope equipped with a micrometer eyepiece. The abbreviations of measurements used in this study are as follows: TL (total body length), TL-H (body length without head), MW (maximum width of body). The ratio TL/MW was also calculated. Measurements of holotypes are added between round brackets. Label data of holotype specimens are cited between quotation marks. A backslash (\) indicates separate labels. Our comments are given between square brackets.
All localities where Microdytes species were recorded in Thailand, Laos, and Cambodia are shown in Fig.
Known localities of Microdytes species in Thailand, Laos, and Cambodia, including literature records, sampling sites and additional records in this study. For those records where specific information of province was not reported, the location was mapped by dotted lines. Ecoregion classification is given following
T Thailand;
L Laos;
C Cambodia;
KAY Kayah-Karen montane rain forest;
NIN northern Indochina subtropical forests;
LUA Luang Prabang montane rain forests;
NAN northern Annamites rain forests;
NKH northern Khorat Plateau moist deciduous forests;
SEI southeastern Indochina dry evergreen forests;
CIN central Indochina dry forests;
CAR Cardamom Mountains rain forests;
CHA Chao Phraya lowland moist deciduous forests.
Cambodia, Koh Hong Province, 20 km SW Koh Hong, Tatai River, 11°34'N, 103°07'E, alt. 50–300 m.
Holotype
(
Microdytes eliasi sp. nov. very closely resembles M. maculatus (Motschulsky, 1860) (Figs
Measurements. TL = 1.64–1.85 mm (1.76 mm), TL-H = 1.49–1.65 mm (1.55 mm), MW = 1.12–1.25 mm (1.24 mm), TL/MW = 1.33–1.44 (1.42). Body regularly oval, moderately convex (Fig.
Coloration. Head reddish brown. Pronotum reddish brown, narrowly dark brown along anterior and posterior margins. Elytron dark brown with yellowish brown markings forming a distinct transverse band near base not reaching suture connected along lateral margin with a post-median transverse lateral band, with a small post-median spot near suture, and a triangular spot near apex (Figs
Sculpture and structure. Head finely, sparsely, and relatively regularly punctured; anterior half to two-thirds finely microreticulate; clypeus not bordered. Pronotum quite regularly, sparsely, and fairly strongly punctured, with coarser punctures along posterior margin; without microreticulation; lateral margins finely bordered, regularly rounded. Elytron quite regularly, moderately densely and fairly strongly punctured, progressively finer and sparser towards lateral margin; without longitudinal rows of stronger punctures; highly polished and shining; without microreticulation. Ventral surface: metacoxae and metasternum strongly but sparsely punctured, abdomen finely and sparsely punctured; without microreticulation.
Male. The two parts of the median lobe expanded laterally at apex in ventral aspect (Figs
Female. Without secondary sexual characters. Sclerotized spermatheca not found.
Variation of markings is shown in Fig.
This species is dedicated to Elias Bramböck, Vienna, Austria. The species epithet is a name in the genitive singular.
In Thailand, this species was collected in small streams at low altitude lower than 200 m (Fig.
Thailand: Saraburi, Sa Kaeo, Chonburi, and Chanthaburi provinces; Cambodia: Koh Hong Province.
Thailand, Chiang Mai Province, Mae Chaem District, Tha Pha, 18°30'46"N, 98°25'25"E, alt. 720 m.
Holotype
(THNHM): ♂, “THAI: Chiang Mai Mae Chaem Dist., Tha Pha St. 166 (alt. 720 m) 15.VIII.2020” [printed white label] \ “HOLOTYPE Microdytes jeenthongi sp. nov. Okada & Wewalka 2022 [printed red label]”. Paratypes (3 exs.): 2♂♂, same data as the holotype (CGW,
Microdytes jeenthongi sp. nov. resembles M. shunichii Satô, 1995 (Fig.
Measurements. TL = 1.77–1.82 mm (1.79 mm), TL-H = 1.23–1.26 mm (1.26 mm), MW = 1.18–1.23 mm (1.23 mm), TL/MW = 1.46–1.50 (1.49). Body regularly oval, moderately convex (Fig.
Coloration. Head reddish brown. Pronotum reddish brown, along the anterior margin narrowly and along the posterior margin more widely dark brown, especially medially. Elytron dark brown with a distinct transverse band at the base not reaching suture, continuing along the margin to a post-median transverse band and a triangular spot near the apex, and a small round post-median spot near suture (Figs
Sculpture and structure. Head finely and sparsely, slightly irregularly punctured; anterior forth finely microreticulate; clypeus not bordered. Pronotum punctured moderately irregularly, finely, and sparsely, very coarsely along posterior margin; without microreticulation; lateral margins finely bordered, regularly rounded. Elytron very sparsely and finely punctured, progressively finer and sparser towards lateral margin; one longitudinal row of punctures distinct; highly polished and shining; without microreticulation. Ventral surface: metasternum and metacoxae very finely, sparsely, and irregularly punctured; abdomen almost without punctures; without microreticulation.
Male. The two parts of the median lobe expanded and pointed at apex forming the unique arrowhead shape in ventral aspect (Fig.
Female. Unknown.
Variation of markings is shown in Fig.
This species is dedicated to Tadsanai Jeenthong, collection manager of National Science Museum, Thailand. The species epithet is a name in the genitive singular.
This species was collected in a small, shallow stream with gravel bottom flowing through a small valley. In this stream, specimens were collected from a restricted point where tree roots were exposed along the river bottom (Fig.
Thailand: Chiang Mai Province.
Laos, Louang Namtha Province, 10 km E Muang Sing, 21°09–10'N, 101°13–15'E, alt. 750–1400 m.
Holotype
(
Microdytes maximiliani sp. nov. resembles M. satoi Wewalka, 1997 in coloration of pronotum and elytra but differs from this species by darker head, larger size, a distinct impression on lateral side in anterior third of elytron (Fig.
Measurements. TL = 1.60–2.00 mm (1.86 mm), TL-h = 1.40–1.80 mm (1.61 mm), MW = 1.30–1.35 mm (1.30 mm), TL/MW = 1.23–1.43 (1.43). Body broad and regularly oval, quite convex (Figs
Coloration. Head dark reddish brown, darker on vertex and along eyes. Pronotum dark brown. Elytron dark brown with yellowish brown markings forming a distinct transverse band near base not reaching suture and lateral margin, a post-median lateral spot often connected with a triangular spot near apex (Figs
Sculpture and structure. Head finely and sparsely punctured, stronger punctures along eyes and on vertex; with fine microreticulation missing on vertex; clypeus not bordered. Pronotum irregularly punctured with sparse fine punctures and strong punctures concentrated along posterior margin and sparsely on disc; without microreticulation; lateral margins finely bordered, scarcely rounded. Elytron quite regularly, moderately densely and fairly strongly punctured, with traces of two longitudinal rows of punctures; highly polished and shining; without microreticulation; with a distinct impression on lateral side in anterior third (Fig.
Male. Median lobe of aedeagus in ventral aspect slightly tapered from base to apex, expanded before apex, apex truncate (Fig.
Female. Without secondary sexual characters. Sclerotized spermatheca not found.
Variation of markings is shown in Fig.
This species is dedicated to Maximilian Bramböck, Vienna, Austria. The species epithet is a name in the genitive singular.
The species was collected in Yunnan in a 1–2-m wide stream flowing through dense primary forest (
Laos: Louang Namtha Province; China: Yunnan Province.
Thailand, Bueng Kan Province, Seka District, Ban Tong, 18°08'16"N, 103°59'35"E, alt. 190 m.
Holotype
(THNHM): ♂, “THAI: Bueng Kan Seka Dist., Ban Tong St. 206 (alt. 190 m) 28.XII.2020 R. Okada leg. \ HOLOTYPE Microdytes sekaensis sp. nov. Okada & Wewalka 2022” [printed red label]. Paratypes (37 exs.): 1♂, with same data as the holotype (CGW); 36 exs., Laos, Bolikhamsay Province, Nam Kading NPA, Tad Paloy campsite, 18°21–23'N, 104°09'E, alt. 250–400 m, 24.–28.V.2011, NHMB Basel Laos 2011 Expedition, M. Geiser, D. Hauk, A. Phantala & E. Vongphachan leg. (CGW, CRO,
Microdytes sekaensis sp. nov. resembles M. hainanensis Wewalka, 1997 and M. schwendingeri Wewalka, 1997 (Figs
Measurements. TL = 1.34–1.36 mm (1.36 mm), TL-h = 0.92–0.93 mm (0.93 mm), MW = 0.99–1.01 mm (1.01 mm), TL/MW = 1.35–1.36 (1.35). Body broadly oval, strongly convex (Fig.
Coloration. Head yellowish brown. Pronotum yellowish brown, along posterior margin narrowly dark brown. Elytron reddish brown to dark brown with two yellowish brown spots: one basal spot not reaching base, one anterior lateral spot continuing along the lateral margin to a post-median lateral spot and a transverse spot near apex, also with a round median spot near suture (Figs
Sculpture and structure. Head very finely and sparsely, slightly irregularly punctured; entirely and distinctly microreticulate; clypeus not bordered. Pronotum quite irregularly, finely, and sparsely punctured on the disc, additionally with coarser punctures at medial part of posterior margin; without microreticulation; lateral margins finely bordered, regularly rounded. Elytron fairly finely, regularly, and moderately densely punctured, progressively finer and sparser towards lateral margin; two longitudinal rows of punctures moderately distinct; highly polished and shining; without microreticulation. Ventral surface: metacoxae and metasternum finely and sparsely punctured, epipleura and abdomen almost without punctures; without microreticulation.
Male. Median lobe of aedeagus in ventral aspect slightly tapered from base to apex and narrowly constricted before apex, apex spoon shaped (Fig.
Female. Without secondary sexual characters. Sclerotized spermatheca not found.
Variation of markings is shown in Fig.
This species is named after the district name of the type locality.
This species was collected in the remaining water pools in a dried-up stream which had a sandy bottom with rich leaf deposits (Fig.
Thailand: Bueng Kan Province; Laos: Bolikhamsay Province.
Thailand, Ubon Ratchathani Province, Si Mueang Mai Dist., Nam Thaeng, 15°32'19"N, 105°24'08"E, alt. 200 m.
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,
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
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.
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
Sculpture and structure. Head finely, sparsely, and relatively regularly punctured; almost entirely microreticulate; clypeus not bordered (Fig.
Male. Median lobe of aedeagus in ventral aspect equally tapered from base to apex, with a small swelling at apex (Fig.
Female. Without secondary sexual characters. Sclerotized spermatheca not found.
Variation of markings is shown in Fig.
This species is named after the popular provincial name of the type locality.
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.
Thailand: Ubon Ratchathani Province; Laos: Savannakhet, Champasak, and Vientiane provinces.
Microdytes akitai
Wewalka, 1997: 17;
Laos, Vientiane Province, Mt. Phou Khao Khouay.
Laos: Bolikhamsay Province. 22 exs., Nam Khading National Bio-Diversity Conservation Area, Tad Paloy campsite, 18°23.17'N, 104°09.65'E, alt. 300 m, forest stream, 8.–11.VII.2010 & 24.–28.V.2011, NHMB Basel Laos 2010 & 2011 Expeditions, M. Brancucci, M. Geiser, D. Hauk, A. Phantala & E. Vongphachan leg. (CGW, CRO,
Habitus of 18 Microdytes akitai 19 M. balkei 20 M. dimorphus 21 M. feryi (paratype, from Myanmar) 22 M. franzi 23 M. gabrielae 24 M. heineri 25 M. maculatus 26 M. mariannae 27 M. menopausis 28 M. paoloi 29 M. pasiricus 30 M. pederzanii 31 M. rocchii 32 M. schoedli 33 M. schoenmanni (from Myanmar) 34 M. schwendingeri 35 M. shepardi 36 M. shunichii 37 M. zetteli. Scale bar: 1.0 mm.
Specimens from Bolikhamsay have more distinct elytral markings and darker head color than in the specimens from the type locality but no other differences have been observed, in particular, in the male genitalia.
Laos: Vientiane and Bolikhamsay (first record) provinces.
Microdytes balkei
Wewalka, 1997: 18;
Thailand, Rayong Province, Khao Chamao NP.
Thailand: Mukdahan Province. 1♂, Phu Pha Thoep N.P., small pools (23), 1.I.2000, Mazzoldi leg. (CGW); Ubon Ratchathani Province. 1♂, 1♀, Nam Yuen District, Dom Pradit St. 240 (alt. 260 m), 22.V.2021, R. Okada leg. (CRO, THNHM); Saraburi Province. 1♀, Kaeng Khoi District, Ched Khot St. 122 (alt. 140 m), 30.V.2020, R. Okada leg. (CRO); Chonburi Province. 2♂♂, 1♀, Ban Bueng District, Khlong Kiu St. 261 (alt. 200 m), 6.XI.2021, R. Okada leg. (CGW, CRO) (Fig.
Laos: Savannakhet Province. 203 exs., 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, CRO,
Cambodia: Koh Hong Province. 12 exs., 20 km SW Koh Hong, Tatai River, 11°34'N, 103°07'E, alt. 50–300 m, 3.–19.V.2005, E. Jendek & O. Šauša leg. (CGW,
Since the figure of the median lobe of this species was not depicted clearly in
Thailand: Mukdahan, Rayong, Trat, Ubon Ratchathani (first record), Saraburi (first record), and Chonburi (first record) provinces, Khao Yai NP [Nakhon Ratchatsima or Nakhon Nayok Province]; Laos (first record): Savannakhet and Sekong provinces; Cambodia (first record): Koh Hong Province.
Microdytes dimorphus
Wewalka, 1997: 22;
Thailand, Nakhon Ratchasima or Nakhon Nayok Province, Khao Yai NP.
Thailand: Chonburi Province. 1♂, Si Racha District, Bang Phra St. 269 (alt. 90 m), 26.XII.2020, R. Okada leg. (CRO) (Fig.
Microdytes dimorphus was described based on a single male specimen from Khao Yai National Park and no additional records are known so far. Therefore, this is the second record of this species.
Thailand: Khao Yai NP [Nakhon Ratchasima or Nakhon Nayok Province] and Chonburi (first record) Province.
Microdytes franzi
Wewalka & Wang, 1998: 65;
Laos, Vientiane Province, Mt. Phou Khao Khouay.
Laos: Bolikhamsay Province. 20 exs., Nam Khading National Bio-Diversity Conservation Area, Tad Paloy campsite, 18°23.17'N, 104°09.65'E, alt. 300 m, forest stream, 8.–11.VII.2010 & 24.–28.V.2011, NHMB Basel Laos 2010 & 2011 Expeditions, M. Brancucci, M. Geiser, D. Hauk, A. Phantala & E. Vongphachan leg. (CGW, CRO,
Laos: Vientiane and Bolikhamsay (first record) provinces.
Microdytes gabrielae
Wewalka, 1997: 24;
Thailand, Phetchabun Province, Huai Nam Phang.
Thailand: Phetchabun Province. 1♂, Phu Hin Rongkla NP, small stream (7), 25.XII.1999, Mazzoldi leg. (CGW) (Fig.
Thailand: Phetchabun and Phitsanulok provinces.
Microdytes heineri
Wewalka, 2011: 23;
China, Yunnan Province, Simao Prefecture.
Thailand: Chiang Mai Province. 8 exs., Mae Taeng District, Pa Pae St. 49 (alt. 1000 m), 15.VI.2019, R. Okada leg. (CGW, CRO, THNHM); 1♂, same district, Kuet Chang St. 170 (alt. 520 m), 16.VIII.2020, R. Okada leg. (CRO) (Fig.
Male specimens have distinct setae on the metacoxae (Fig.
Thailand: Nan and Chiang Mai (first record) provinces; Laos: Luang Namtha and Luang Prabang provinces; China: Yunnan Province.
Hydrovatus maculatus
Motschulsky, 1860: 42;
Desmopachria maculatus: Gschwendtner 1936: 367;
Microdytes maculatus:
“Ind or”, “Dohen [a place with this name exists in Pakistan, Jammu and Kashmir Province, but it is very unlikely that this is the type locality]”.
Thailand: Chiang Mai Province. 6♂♂, 1♀, Chom Thong District, Ban Luang St. 165 (alt. 360 m), 15.VIII.2020, R. Okada leg. (CGW, CRO) (Fig.
Diagnostic characters of Microdytes species. 38 Impression of lateral side (M. maximiliani sp. nov.) 39 ventral surface A with setae (M. heineri) B with very coarse punctures (M. schoedli) C with coarse punctures (M. maculatus) D with fine punctures (M. balkei) E with very fine punctures (M. jeenthongi sp. nov.) 40 clypeus bead A not bordered (M. ubonensis sp. nov.) B finely bordered (M. schwendingeri) C produced (M. dimorphus).
Laos: Luang Prabang Province. 4 exs., Thong Khan, 19°35'N, 101°58'E, alt. ca. 750 m, 11–12.V.2002, V. Kubáň leg. (CGW,
The lectotype of Microdytes maculatus (Fig.
41 Lectotype of Microdytes maculatus (photograph by Christophe Rivier, Muséum national d’histoire naturelle, Paris) 42 median lobe of A M. maculatus from northern Thailand B from northeastern Thailand C M. eliasi sp. nov. 43 paramere of A M. maculatus from northern Thailand B from northeastern Thailand C M. eliasi sp. nov.
There is also a geographic variation in the shapes of the median lobe and the apical part of the parameres. In specimens from Myanmar, northern Thailand, and China, the two parts of the median lobe have obtuse apical medial angles (Fig.
India: southern Andaman Islands; Myanmar: Chin and Shan states, Saganing Division; Thailand: Chiang Mai, Chiang Rai (first record), Lampang (first record), Lamphun, Mae Hong Son, Uttaradit (first record), Phetchabun (first record), Bueng Kan (first record), Mukdahan, Nakhon Phanom (first record), Sakon Nakhon (first record), Ubon Ratchathani (first record), and Kantchanaburi provinces, Khao Yai NP [Nakhon Ratchasima or Nakhon Nayok Province]; Laos: Vientiane, Luang Prabang (first record) and Khammouan provinces; China: Yunnan Province.
Microdytes mariannae
Wewalka, 1997: 28;
Thailand, Phetchabun Province, Nam Nao.
Thailand: Phetchabun Province. 8♂♂, 10♀♀, Lom Kao District, Ban Noen St. 187 (alt. 1620 m), 20.IX.2020, R. Okada leg. (CGW, CRO, THNHM) (Fig.
Thailand: Phetchabun and Loei provinces.
Microdytes menopausis
Wewalka, 1997: 29;
Thailand, Khao Yai NP.
Thailand: Nakhon Phanom Province. 1♂, 2♀♀, Bang Phaeng District, Phai Lom St. 203 (alt. 200 m), 27.XII.2020, R. Okada leg. (CGW, CRO); Sakon Nakhon Province. 1♀, Tao Ngoi District, Nan Tan St. 210 (alt. 310 m), 29.XII.2020, R. Okada leg. (CRO) (Fig.
Laos: Khammouan Province. 1♂, Nakai-Nam Theun NPA, Ban Navang env., 17°57–59'N, 105°13–16'E, alt. 600–750 m, 18.–21.V.2012, NHMB Basel, Laos 2012 Expedition, M. Brancucci, M. Geiser, K. Phanthavong & S. Xayalath leg. (
Thailand: Trat, Nakhon Phanom (first record), Sakon Nakhon (first record), and Ubon Ratchathani (first record) provinces, Khao Yai NP [Nakhon Ratchasima or Nakhon Nayok Province]; Laos: Khammouan, Savannakhet (first record) and Sekong provinces.
Microdytes paoloi
Wewalka, 2011: 24;
Thailand, Phetchabun Province, Phu Hin Rongkla NP.
Thailand: Phetchabun Province. 1♂, paratypus, Phu Hin Rongkla NP, small stream, alt. 1250 m (4), 25.XII.1999, Mazzoldi leg. (CMW) (Fig.
Thailand: Phetchabun and Loei provinces.
Hydrovatus pasiricus Csiki, 1938: 126 (including var. simplicor and var. unicolor).
Microdytes pasiricus:
Indonesia, Central Java, Sarangan near Lake Pasir.
Thailand: Chiang Rai Province. 3♂♂, Wiang Kaen District, Muang Yai St. 71 (alt. 440 m), 11.VIII.2019, R. Okada leg. (CGW, CRO) (Fig.
Thailand: Chiang Rai (first record), Chiang Mai (first record) and Phetchabun provinces; Philippines: Busuanga, Luzon, Mindoro, Palawan; Singapore; Indonesia: Java.
Microdytes pederzanii
Wewalka, 2011: 25;
Thailand, Phetchabun Province, Phu Hin Rongkla NP.
Thailand: Phetchabun Province. 2♀♀, Lom Kao District, Ban Noen St. 187 (alt. 1620 m), 20.IX.2020, R. Okada leg. (CRO); Uttaradit Province. 1♂, 1♀, Nam Pad District, Phu Soi Dao NP, pine forest, 12.VII.2020, T. Jeenthong leg. (THNHM) (Fig.
Thailand: Phetchabun and Uttaradit (first record) provinces.
Microdytes rocchii
Wewalka, 2011: 26;
Laos, Khammuan Province, Ban Khoun Ngeun.
Laos: Khammouan Province. 1♀, Ban Khon Ngeun, 18°07'N, 104°29'E, alt. ca 200 m, 19.–31.V.2001, Pacholátko leg. (CGW) (Fig.
Laos: Khammuan and Savannakhet (first record) provinces.
Microdytes schoedli
Wewalka, 1997: 33;
Thailand, Phetchabun Province, Nam Nao NP.
Thailand: Chiang Mai Province. 2♀♀, Chiang Dao District, Ping Khong St. 226 (alt. 430 m), 20.III.2021, R. Okada leg. (CRO); Lampang Province. 1♂, 1♀, Thoen District, Mae Pa St. 197 (alt. 200 m), 15.XI.2020, R. Okada leg. (CRO); Mae Hong Son Province. 1♂, Pai District, Thung Yao St. 50 (alt. 610 m), 15.VI.2019, R. Okada leg. (CRO); 2♂♂, 2♀♀, Muang Mae Hong Son District, Pha Bong St. 250 (alt. 480 m), 13.VI.2021, R. Okada leg. (CGW, CRO) (Fig.
Laos: Khammouan Province. 1♂, 2♀♀, Nakai-NamTheun NPA, Ban Navang env., 17°57–59'N, 105°13–16'E, alt. 600–750 m, 18.–21.V.2012, NHMB Basel, Laos 2012 Expedition, M. Brancucci, M. Geiser, K. Phanthavong & S. Xayalath leg. (
Thailand: Chiang Mai, Lampang (first record), Mae Hong Son (first record), Phetchabun, Tak, Mukdahan, and Kanchanaburi (first record) provinces; Laos: Khammouan (first record), Savannakhet (first record) and Sekong provinces.
Microdytes schwendingeri
Wewalka, 1997: 36;
Thailand, Sakon Nakhon Province, Phu Pan NP.
Thailand: Nakhon Phanom Province. 1♂, 1♀, Bang Phaeng District, Phai Lom St. 203 (alt. 200 m), 27.XII.2020, R. Okada leg. (CRO, THNHM) (Fig.
Laos: Savannakhet Province, 1♀, 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. (
Some specimens from Laos have less distinct elytral markings but no other differences from typical specimens have been observed.
Thailand: Nakhon Phanom (first record) and Sakon Nakhon provinces; Laos (first record): Savannakhet and Champasak provinces.
Microdytes shepardi
Wewalka, 1997: 37;
Thailand, Phetchabun Province, Nam Nao NP.
Thailand: Chiang Mai Province. 1♂, 1♀, Chiang Dao District, Ping Khong St. 226 (alt. 430 m), 20.III.2021, R. Okada leg. (CRO); Chiang Rai Province. 1♂, Wiang Kaen District, Muang Yai St. 71 (alt. 440 m), 2.VIII.2019, R. Okada leg. (CRO); Uthai Thani Province. 5♂♂, 2♀♀, Ban Rai District, Kaen Makrut St. 128 (alt. 440 m), 20.VI.2020, R. Okada leg. (CGW, CRO, THNHM) (Fig.
Laos: 1♂, Luang Prabang Province, Thong Khan, 19°35'N, 101°58'E, alt. ca. 750 m, 11.–12.V.2002, V. Kubáň leg. (
Thailand: Chiang Mai, Chiang Rai (first record), Mae Hong Son, Phetchabun, Uthai Thani (first record), Chaiyaphum and Sakon Nakhon provinces; Laos: Luang Prabang Province; China: Yunnan Province.
Microdytes shunichii
Satô, 1995: 313;
Microdytes holzmanni Wewalka & Wang, 1998: 66.
Microdytes holzmannorum: Nilsson 2007: 51 (as unjustified emendation of holzmanni).
Vietnam, Vinh Phuc Province, Mt. Tam Dao.
Thailand: Phetchabun Province. 1♀, Lom Kao District, Ban Noen St. 187 (alt. 1620 m), 20.IX.2020, R. Okada leg. (CRO); 3♂♂, 2♀♀, same locality, St. 294, 18.VI.2022, R. Okada leg. (CGW, CRO, THNHM).
Laos: Luang Namtha Province. 62 exs., 10 km E Muang Sing, Ban Oudomsinh / B. Nam Det / B. Nam Mai, 21°09–10'N, 101°13–15'E, 750–1400 m, 14.–20.V.2011, NHMB Basel, Laos 2011 Expedition, D. Hauk & M. Geiser (CGW, CRO,
Thailand: Nan, Chiang Mai, and Phetchabun (first record) provinces; Laos: Phongsali (first record), Luang Namtha (first record), Oudomxai, Luang Prabang (first record), Vientiane, Khammouan, Savannakhet (first record), and Attapeu (first record) provinces; China: Yunnan Province, Hong Kong; Vietnam: Vinh Phuc Province.
Microdytes wewalkai
Bian & Ji, 2009: 37;
China, Hainan, Lingtou (Ledong) County, Jianfengling NR.
Laos: Attapeu Province. 3♂♂, 2♀♀, Dong Amphan National Bio-Diversity Conservation Area, Nong Fa (crater lake) env., 15°05.9'N, 107°25.6'E, alt. ca. 1160 m, 30.IV.–6.V.2010, J. Hájek leg. (CGW,
Specimens from Laos have two transverse yellowish red markings on both sides of the middle of pronotum while in specimens from China (Hainan) it is completely black, but no other differences have been observed.
Laos (first record): Attapeu Province; China: Hainan Province.
Microdytes zetteli
Wewalka, 1997: 41;
Thailand, Chiang Mai Province, Doi Suthep.
Thailand: Chiang Mai Province. 12 exs., Mae Taeng District, Pa Pae St. 49 (alt. 1000 m), 15.VI.2019, R. Okada leg. (CGW, CRO, THNHM); 2♂♂, Mae Chaem District, Tha Pha St. 136 (alt. 720 m), 4.VII.2020, R. Okada leg. (CGW, CRO); 1♂, same locality St. 166 (alt. 720 m), 15.VIII.2020, R. Okada leg. (THNHM) (Fig.
Laos: 4 exs., Luang Prabang Province, 5 km W Ban Song Cha, 20°33–4'N, 102°14'E, alt. ca. 1200 m, 1.–16.V.1999, V. Kubáň leg. (CGW,
Myanmar: Shan State; Thailand: Chiang Mai, Chiang Rai (first record) and Mae Hong Son provinces; Laos: Luang Prabang Province.
Microdytes schoenmanni
Wewalka, 1997: 34;
Thailand, Trat Province, Koh Chang Island, Klong Prao.
Myanmar: 1♂, Shan State, N Aungban, halfway between Pindaya and Ye’ngan, 20°58.271'N, 96°32.488'E, ca. alt. 1241 m, stream, 10.VI.2004, Shaverdo leg. (CGW) (Fig.
India: Darjeeling; Nepal; Myanmar: Chin and Shan states, Saganing and Tanintharyi divisions; Thailand: Trat Province, Khao Yai NP [Nakhon Ratchasima or Nakhon Nayok Province]; Laos: Attapeu Province; China: Yunnan Province.
Microdytes akitai Wewalka, 1997 Laos
Microdytes balkei Wewalka, 1997 Thailand, Laos, Cambodia
Microdytes dimorphus Wewalka, 1997 Thailand
Microdytes eliasi Wewalka & Okada, sp. nov. Thailand, Cambodia
Microdytes franzi Wewalka & Wang, 1998 Laos
Microdytes gabrielae Wewalka, 1997 Thailand
Microdytes heineri Wewalka, 2011 Thailand, Laos, China
Microdytes jeenthongi Okada & Wewalka, sp. nov. Thailand
Microdytes maculatus (Motschulsky, 1860) India, Myanmar, Thailand, Laos, China
Microdytes mariannae Wewalka, 1997 Thailand
Microdytes maximiliani Wewalka & Okada, sp. nov. Laos, China
Microdytes menopausis Wewalka, 1997 Thailand, Laos
Microdytes paoloi Wewalka, 2011 Thailand
Microdytes pasiricus (Csiki, 1938) Thailand, Philippines, Singapore, Indonesia
Microdytes pederzanii Wewalka, 2011 Thailand
Microdytes rocchii Wewalka, 2011 Laos
Microdytes schoedli Wewalka, 1997 Thailand, Laos
Microdytes schoenmanni Wewalka, 1997 India, Nepal, Myanmar, Thailand, Laos, China
Microdytes schwendingeri Wewalka, 1997 Thailand, Laos
Microdytes sekaensis Okada & Wewalka, sp. nov. Thailand, Laos
Microdytes shepardi Wewalka, 1997 Thailand, Laos, China
Microdytes shunichii Satô, 1995 Thailand, Laos, China, Vietnam
Microdytes ubonensis Okada & Wewalka, sp. nov. Thailand, Laos
Microdytes wewalkai Bian & Ji, 2009 Laos, China
Microdytes zetteli Wewalka, 1997 Myanmar, Thailand, Laos
1 | Elytron with a distinct impression on lateral side in anterior third (Fig. |
M. maximiliani sp. nov. |
– | Elytron without impression on lateral side | 2 |
2 | Punctures on metacoxae very coarse (Fig. |
3 |
– | Punctures on metacoxae fine (Fig. |
18 |
3 | Elytra with two postmedian longitudinal bands (Fig. |
M. paoloi |
– | Elytra without longitudinal band | 4 |
4 | Pronotum dark brown to black with a transverse reddish-brown band on each side. TL: 1.90–2.10 mm | M. wewalkai |
– | Pronotum without transverse band | 5 |
5 | Body oval or rhomboid (Figs |
6 |
– | Body oval; small species TL: 1.30–1.40 mm | 11 |
6 | Elytra without a post-median spot near suture | 7 |
– | Elytra with a post-median spot near suture | 13 |
7 | Pronotum predominantly reddish brown to dark brown; metacoxae of male with distinct setae (Fig. |
M. heineri |
– | Pronotum predominantly yellowish brown; metacoxae without setae | 8 |
8 | Body regularly oval; cypeus not bordered; TL: 1.70–2.00 mm | M. shepardi |
– | Body rhomboid; clypeus bordered at least in the middle | 9 |
9 | Elytra predominantly yellowish brown; clypeus rounded and finely bordered; TL: 1.40–1.60 mm | M. pasiricus |
– | Elytra predominantly dark brown; clypeus straightened and slightly bordered in the middle (Fig. |
10 |
10 | Apical three sternites distinctly punctured; the coarser punctures on the elytra similar in size; TL: 1.75–1.85 mm | M. dimorphus |
– | Apical three sternites almost without punctures; the coarser punctures on the elytra distinctly of two kinds; TL: 1.40–1.70 mm | M. menopausis |
11 | Body oblong oval; pronotum predominantly dark brown; TL: 1.25–1.40 mm | M. ubonensis sp. nov. |
– | Body broadly oval; pronotum predominantly yellowish brown | 12 |
12 | Elytral markings with distinct transversal band at the base and without a post-median spot near the suture; TL: 1.30–1.40 mm | M. schwendingeri |
– | Elytral markings with two indistinct spots at the base and with a post-median spot near the suture; TL: 1.34–1.36 mm | M. sekaensis sp. nov. |
13 | Elytral punctures consisting of one kind | 14 |
– | Elytral punctures consisting of two kinds (e.g., Fig. |
15 |
14 | Body regularly oval; the two parts of the median lobe obtuse to right apical medial angles but not expanded laterally at apex; the tips of paramere narrow to rounded but not constricted; TL: 1.60–1.90 mm | M. maculatus |
– | Body more regularly oval; the two parts of the median lobe expanded laterally at apex; the tips of paramere constricted; TL: 1.64–1.85 mm | M. eliasi sp. nov. |
15 | Body oblong oval; TL: 1.90–2.15 mm | M. schoedli |
– | Body regularly oval | |
16 | Elytral marking near the base indistinct; bigger punctures on elytra coarser; TL: 1.60–1.75 mm | M. pederzanii |
– | Elytral marking near the base distinct; bigger punctures on elytra less coarse | 17 |
17 | Post-median spot near the suture rounded; TL: 1.80–1.85 mm | M. rocchii |
– | Post-median spot near the suture longitudinal; TL: 2.10–2.25 mm | M. mariannae |
18 | Body oblong oval; TL: 1.70–1.80 mm | M. balkei |
– | Body regularly oval | 19 |
19 | Elytral marking near the base indistinct and small spot; TL: 1.45–1.55 | M. gabrielae |
– | Elytral marking near the base distinct | 20 |
20 | Elytral marking dilated or waved at the shoulder; TL: 1.40–1.65 mm | 21 |
– | Elytral marking broad transverse band at the shoulder; TL: 1.60–1.90 mm | 22 |
21 | Head dark brown; pronotum dark brown; TL: 1.40–1.60 mm | M. franzi |
– | Head yellowish brown; pronotum reddish brown; 1.40–1.65 mm | M. schoenmanni |
22 | Pronotal punctures coarser; elytral punctures stronger; TL: 1.60–1.70 mm | M. akitai |
– | Pronotal punctures spacer; elytral punctures finer | 23 |
23 | Pronotum predominantly yellowish brown; elytral punctures fine but distinct; TL: 1.65–1.90 mm | M. shunichii |
– | Pronotum predominantly reddish brown; elytral punctures very fine and very sparse | 24 |
24 | Head moderately finely and sparsely punctured; TL: 1.55–1.70 mm | M. zetteli |
– | Head finely and sparsely punctured; TL: 1.79–1.82 mm | M. jeenthongi sp. nov. |
The discovery of five new species with three first country records and 40 first regional records from Thailand, Laos, and Cambodia shows how poorly the Dytiscidae fauna of these countries is known. The data on species diversity of Microdytes species are summarized in Table
Summary of distribution types of Microdytes species in main ecoregions in Thailand, Laos, and Cambodia. T Thailand L Laos C Cambodia KAY Kayah-Karen montane rain forest NIN northern Indochina subtropical forests LUA Luang Prabang montane rain forests NAN northern Annamites rain forests NKH northern Khorat Plateau moist deciduous forests SEI southeastern Indochina dry evergreen forests CIN central Indochina dry forests CAR Cardamom Mountains rain forests CHA Chao Phraya lowland moist deciduous forests.
Distribution pattern | Microdytes species | Distribution records | Limited to | Main ecoregions in Thailand, Laos, and Cambodia | N | Ratio | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Thailand | Laos | Cambodia | three countries | KAY | NIN | LUA | NAN | NKH | SEI | CIN | CAR | CHA | ||||
Widespread | maculatus | + | + | T | T | T/L | L | T | T | T | 5 | 20% | ||||
pasiricus | + | T | T | T | ||||||||||||
schoedli | + | + | + | T | T | T/L | L | T/L | ||||||||
schuichii | + | + | T | L | L | L | L | L | ||||||||
schoenmanni | + | + | T | L | T | |||||||||||
N Thailand and Laos | heineri | + | + | T | T/L | 9 | 36% | |||||||||
jeenthongi sp. nov. | + | + | T | |||||||||||||
maximiliani sp. nov. | + | L | ||||||||||||||
shepardi | + | + | T | T | T/L | |||||||||||
zetteli | + | + | T | T | L | |||||||||||
(limited to N Thailand) | gabrielae | + | + | T | ||||||||||||
mariannae | + | + | T | |||||||||||||
paoloi | + | + | T | |||||||||||||
pederzanii | + | + | T | |||||||||||||
NE Thailand to S Laos | akitai | + | + | L | L | 6 | 24% | |||||||||
franzi | + | + | L | L | ||||||||||||
rocchii | + | + | L | |||||||||||||
schwendingeri | + | + | + | T | L | T | ||||||||||
sekaensis sp. nov. | + | + | + | L | T | |||||||||||
ubonensis sp. nov. | + | + | + | L | L | L | T | |||||||||
NE and E Thailand to S Laos | balkei | + | + | + | + | L | T | L | T/C | T | 5 | 20% | ||||
dimorphus | + | + | T | T | ||||||||||||
eliasi sp. nov. | + | + | + | T | T/C | T | ||||||||||
menopausis | + | + | + | L | T | T | T | T | ||||||||
wewalkai | + | L | ||||||||||||||
Total recorded species | 20 | 17 | 2 | 16 | 8 | 8 | 13 | 10 | 6 | 8 | 8 | 4 | 3 | 25 | 100% | |
Ratio | 64% | 32% | 32% | 52% | 40% | 24% | 32% | 32% | 16% | 12% |
In view of species diversity by ecoregions, LUA has the highest number of species (13 species, 52% of total fauna). This region comprises four species which occur only in one ecoregion. NAN has the second highest number of species (10 species, 40%), including the two new species M. sekaensis sp. nov. and M. ubonensis sp. nov. KAY, NIN, SEI, and CIN also have high numbers of species (8 species, 32%), including M. jeenthongi sp. nov., M. maximiliani sp. nov., M. ubonensis sp. nov., and M. eliasi sp. nov., respectively.
The distribution pattern of Microdytes species recorded from the three countries represents four types: 1) widespread type, occurring throughout continental Southeast Asia to adjacent countries (5 species, 20%); 2) northern type, distributed mainly from northern Thailand and Laos to adjacent countries (9 species, 36%); 3) central type, recorded only from northeastern Thailand to southern Laos (6 species, 24%); 4) eastern type, occurring in northeastern and eastern Thailand and southern Laos (5 species, 20%). The conclusions made above are not definitive because there are still many unexplored areas.
Most of the Microdytes specimens examined in this study were collected at lotic habitats associated with running water flowing under primary or secondary forests, and many species were sympatric. At one locality of Tha Pha, northern Thailand, located at Kayah-Karen montane rain forests, four species were collected from the same small stream (Fig.
Collecting localities of Microdytes species in Thailand 45 Ban Kaeng, Sa Kaeo Province, one of the localities of M. eliasi sp. nov. 46 Tha Pha, Chiang Mai Province, type locality of M. jeenthongi sp. nov. 47 Ban Tong, Bueng Kan Province, type locality of M. sekaensis sp. nov. 48 Nam Thaeng, Ubon Ratchathani Province, type locality of M. ubonensis sp. nov.
Unlike the northern region of Thailand, where diving beetle surveys have been carried out relatively many times (e.g., by Dr. William D. Shepard, Dr. Manfred A. Jäch, Dr. Herbert Zettel; pers. comm.), a large part of this country remained poorly explored, especially Isan (northeastern region) and the eastern regions. Our study detected three new Microdytes species from these unexplored areas. From the southern region no Microdytes species have been reported so far, although two species (Microdytes elgae Hendrich, Balke & Wewalka, 1995 and M. pasiricus) were recorded from Singapore, situated at the southern end of the Malay Peninsula (
We thank Jiří Hájek (Prague, Czech Republic), Isabelle Zürcher-Pfander (Basel, Switzerland), Manfred A. Jäch (Vienna, Austria), and Tadsanai Jeenthong (Pathum Thani, Thailand) for providing study material. Sincere gratitude to Antoine Mantilleri (Paris, France) for checking type material. Thanks also go to Michael Cota (Pathum Thani, Thailand) for correcting the English of this manuscript. We also offer thanks to Helena Shaverdo (Vienna, Austria) and Veera Vilasri (Pathum Thani, Thailand) for their supporting loan material.