Copelatus nakai Jiang, Jia & Hajek 2025, sp. nov.
Creators: name: Jiang, Zhuo-Yin
name: Hájek, Jiří
name: Zheng, Yi-Li
name: Jia, Feng-Long
name: Wang, Bei-Xin
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Dytiscidae
Copelatus
Copelatus nakai

description: Copelatus nakai Jiang, Jia & Hájek, sp. nov.
(Figs 1C–D, 2E–G)
Type locality. Laos, Khammouane Province, Nakai env., ca. 17°43’N, 105°09’E, 500–600 m.
Type material. Holotype: ♂ (NMPC), labelled: “ LAOS centr., 22.v-8.vi.2001 / Khammouan prov. / NAKAI env., alt. 500–600 m, / N 17°43’, E 105°09’, / E. Jendek & O. Šauša leg. [p] // HOLOTYPUS ♂ / COPELATUS / nakai sp. nov. / Jiang, Jia & Hájek det. 2024 [red label, p]”. Paratypes: 3 ♀ (NMPC), same label data as holotype. All paratypes with the appropriate printed red label.
Description of holotype. Habitus (Fig. 1C) oblong-oval, with continuous outline, broadest in anterior fourth of elytral length, dorsally slightly convex. Dorsal surface submatt.
Colouration. Head reddish brown, darker posterior to eyes; clypeus and labrum orange. Pronotum brown blackish on disc, laterally broadly reddish Elytra brown with lighter, orange brown apex and sides laterally from elytral stria 6, and orange broad basal transverse band. Ventral surface brown blackish. Appendages orange to red.
Head. Moderately broad, ca. 0.7× width of pronotum, transversely semicircular. Anterior margin of clypeus indistinctly concave. Antenna with antennomeres long and slender. Reticulation consisting of fine, well impressed isodiametric polygonal meshes. Punctation double; several large setigerous punctures present in fronto-clypeal depressions, frontal depressions at level of anterior margin of eyes, and in depressions alongside inner margin of eyes; fine punctures smaller and sparser on clypeus, becoming larger and denser posteriorly.
Pronotum. Transverse (width/length ratio = 2.5), broadest between posterior angles, lateral margins moderately curved. Lateral sides with thin beading perceptible only in dorsolateral view. Reticulation and punctation similar to that of head; rows of coarse setigerous punctures present along anterior margin and laterally close to sides; several punctures present also in shallow basolateral depressions along basal margin. Basolateral depressions and sides close to posterior corners with several short longitudinal striolae. Centre of disc with short shallowly impressed medial longitudinal smooth line.
Elytra. Base of elytra as broad as pronotal base; lateral margins of elytra almost parallel in basal third, then narrowing to apex. Six discal and one submarginal longitudinal striae present on each elytron: striae 2–4 beginning shortly behind base, striae 1, 5–6 beginning more posteriorly; stria 1 longest, ending close to apex; striae 2–5 somewhat shorter, ending subapically; stria 6 ending at apical fourth; submarginal stria long, beginning before elytral mid-length and ending subapically, at same level as dorsal striae 2–5. Reticulation similar to that of head and pronotum, but less impressed. Punctation consisting of scattered very fine sparse punctures and coarse setigerous punctures present along elytral striae and lateral margins of elytra.
Legs. Protibia modified, angled proximally, distinctly broadened distally, club shaped. Pro- and mesotarsomeres 1–3 distinctly broadened, with rows of adhesive setae on their ventral side; claws simple. Longer spur of metatibia straight.
Ventral side. Prosternum medially elevated, anterior margin sinuate. Prosternal process lanceolate, in cross-section convex, distinctly bordered laterally; reticulation not perceptible. Metaventrite with microsculpture consisting of polygonal meshes; lateral parts of metaventrite (“metasternal wings”) tongue-shaped, slender. Metacoxal lines nearly complete, absent only very close to metaventrite. Metacoxal plates covered with long oblique strioles; reticulation consisting of oblique elongate polygonal meshes. Metacoxal processes rounded at posterior margin. Abdominal ventrites I–II with longitudinal strioles; ventrites III–IV with oblique strioles laterally. Tuft of setae present medially on ventrites III–V; ventrite VI with setigerous punctures laterally. Abdominal reticulation consisting of elongate polygonal meshes, longitudinal on ventrites I–II, oblique on ventrite III and transverse on ventrites IV–VI. Punctation consisting of fine, sparsely distributed punctures.
Male genitalia. Median lobe of aedeagus sickle-shaped in lateral view (Fig. 2E), broader in basal half and slender in apical half, distinctly broadened subapically, apex rounded; at mid-length with two irregularly shaped auricular processes, which are placed laterally to longitudinal axis of median lobe. In ventral view, median lobe turned right in apical fifth of its length (Fig. 2F). Parameres as in Fig. 2G.
Female. Female identical to male in habitus. Protibia simple, not angled proximally and only slightly broadened distally; pro- and mesotarsomeres not broadened, without adhesive setae. Head in posterior part between eyes with several short longitudinal or oblique striolae; whole surface of pronotum covered with rather densely distributed long longitudinal striolae; disc of elytra in basal two thirds covered with moderately densely distributed long longitudinal striolae, striolae becoming shorter and sparser posteriad and laterad (Fig. 1D).
Variability. No substantial variability, except for sexual dimorphism, can be seen in the limited number of specimens available to us.
Measurements. TL: 4.6–5.0 mm (mean value: 4.8 ± 0.1 mm); holotype: 5.0 mm. TL-h: 4.1–4.5 mm (mean value: 4.3 ± 0.1 mm); holotype: 4.5 mm. MW: 2.2–2.4 mm (mean value: 2.3 ± 0.1 mm); holotype: 2.4 mm.
Differential diagnosis. Based on the presence of six dorsal striae and a submarginal elytral stria, Copelatus nakai sp. nov. can be classified within the Copelatus irinus group sensu Guignot (1961: 662). The characteristic shape of the median lobe with two auricular processes on the ventral side (Figs 2E–F) distinguishes the new species from all other Oriental Copelatus, except for C. liwu sp. nov. described above. Both species can only be distinguished based on the shape of the male genitalia: the median lobe is more regularly curved in lateral view in C. nakai sp. nov. than in C. liwu sp. nov.; the apex of the median lobe is not broadened in C. liwu sp. nov., but subapically distinctly broadened in C. nakai sp. nov.; one auricular process is placed in longitudinal axis of the median lobe and the other one is perpendicular to that process in C. liwu sp. nov., whereas both processes are positioned somewhat more laterally from the longitudinal axis of the median lobe in C. nakai sp. nov.; both species differ also in the shape of the auricular processes (see Figs 2A–B and 2E). As for now, females of C. liwu sp. nov. are identical to males in elytral sculpture (i.e. without striolae), but females of C. nakai sp. nov. have the disc of elytra in basal two thirds covered with moderately densely distributed long longitudinal striolae; however, we are aware that this observation can only be caused by the limited number of specimens available for the study and both female forms may occur in any of those species.
Etymology. The species is named after its type locality, Nakai Village in Khammouane Province, Central Laos; the name is a noun in the nominative singular, standing in apposition.
Distribution. Copelatus nakai sp. nov. is so far only known from the type locality in central Laos (Fig. 4).
description: Published as part of Jiang, Zhuo-Yin, Hájek, Jiří, Zheng, Yi-Li, Jia, Feng-Long & Wang, Bei-Xin, 2025, Two new species of Oriental Copelatus Erichson, 1832, with additional records of the genus from China (Coleoptera: Dytiscidae: Copelatinae), pp. 42-50 in Zootaxa 5632 (1) on pages 45-48, DOI: 10.11646/zootaxa.5632.1.2, http://zenodo.org/record/15371613