Microdytes sekaensis Okada & Wewalka, 2023

Okada, Ryohei, Jaitrong, Weeyawat & Wewalka, Guenther, 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, pp. 87-119 : 87

Microdytes sekaensis Okada & Wewalka sp. nov.

Figs 5 , 10 , 15

Type locality.

Thailand, Bueng Kan Province, Seka District, Ban Tong, 18°08'16"N, 103°59'35"E, alt. 190 m.

Type material.

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, NMB, NMP). All paratypes are provided with printed red paratype labels.

Diagnosis.

Microdytes sekaensis sp. nov. resembles M. hainanensis Wewalka, 1997 and M. schwendingeri Wewalka, 1997 (Figs 34 , 40B ) in habitus and size but differs by elytral markings and clypeus not bordered. Size and coloration of M. sekaensis sp. nov. is also similar to those of M. gabrielae Wewalka, 1997 (Fig. 23 ), but it is distinguishable from the latter by the more rounded-oval body and finely and sparsely punctured ventral surface.

Description.

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. 5 ).

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 5 , 10 ). Ventral surface predominantly yellowish brown. Legs, antennae and palpi yellowish brown.

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. 15A ); in lateral aspect slightly curved with an arrowhead shaped apical expansion (Fig. 15B ). Paramere narrowly trapezoid in lateral aspect (Fig. 15C, D ).

Female. Without secondary sexual characters. Sclerotized spermatheca not found.

Variation.

Variation of markings is shown in Fig. 10 .

Etymology.

This species is named after the district name of the type locality.

Habitat.

This species was collected in the remaining water pools in a dried-up stream which had a sandy bottom with rich leaf deposits (Fig. 47 ).

Distribution.

Thailand: Bueng Kan Province; Laos: Bolikhamsay Province.

Figures

Figures 2 - 6. Habitus of 2 Microdytes eliasi sp. nov., female, paratype 3 M. jeenthongi sp. nov., male, holotype 4 M. maximiliani sp. nov., male, holotype 5 M. sekaensis sp. nov., male, holotype 6 M. ubonensis sp. nov., male, holotype. Scale bar: 1.0 mm.

Figures 7 - 11. Variation of markings of 7 Microdytes eliasi sp. nov. 8 M. jeenthongi sp. nov 9 M. maximiliani sp. nov. 10 M. sekaensis sp. nov. 11 M. ubonensis sp. nov. Scale bar: 1.0 mm.

Figures 15, 16. 15 Microdytes sekaensis sp. nov. 16 M. ubonensis sp. nov. 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.

Figures 18 - 37. 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.

Figures 38 - 40. 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).

Figures 45 - 48. 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.