Austrelatus riberai, Hájek & Shaverdo, 2024

Hájek, Jiří & Shaverdo, Helena, 2024, Two new species of Austrelatus diving beetles from continental Southeast Asia, linking the distribution area of the genus (Coleoptera: Dytiscidae: Copelatinae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 64 (2), pp. 243-247 : 246-247

Austrelatus riberai sp. nov.

( Figs 2, 5–6 )

Type locality. Myanmar, Shan State, SE of Mintaingbin Forest Camp, ca. 20°55.64′N 96°33.63′E.

Type material. HOLOTYPE: Ô ( NHMW),labelled: ‘ MYANMAR (151) Shan State / SE Mintaingbin Forest Camp / forest pools and in leaf litter / near stream, 17.06.2004 / leg. Shaverdo & Schillhammer [p] // HOLOTYPE Ô / AUSTRELATUS / riberai sp. nov. / J. Hájek & H. Shaverdo det. 2024 [p, red label]’. PARATYPE: 1 Ô, labelled: ‘ MYANMAR: Shan State / Inle Lake, E-shore, 13.5.1999 / 10 km S Nyaungshwe, 940 m / 20°36.48′N 96°56.53′E / leg.Schillhammer & Schuh (39c) [p]’ ( NMPC).The paratype is provided with the respective red printed label.

Description. Male holotype. Habitus ( Fig. 2 ) elongate oblong oval, broadest in anterior third of elytral length, dorsally convex; body outline continuous, without angle between base of pronotum and elytra. Dorsal surface submatt.

Colouration. Head dark brown, clypeus orange; pronotum dark brown, laterally broadly orange, anterior and posterior margins orange-brown translucent; elytral disc dark brown, with broad, irregularly shaped, basal orange band reaching suture, lateral sides orange; appendages orange; ventral side brown.

Head moderately broad, ca. 0.71× width of pronotum, semicircular. Anterior margin of clypeus indistinctly concave. Antenna with antennomeres long and slender. Reticulation consisting of moderately deeply impressed polygonal isodiametric meshes. Punctation double, consisting of coarse setigerous punctures and fine punctures spread sparsely on surface; row of coarse punctures present alongside inner margin of eyes, several punctures present at frontal level of eyes, and antero-laterally to eyes in fronto-clypeal depressions.

Pronotum transverse (width/length ratio = 2.40), broadest before posterior angles, lateral margins moderately curved. Lateral sides with beading very thin and indistinct. Reticulation similar to that of head. Punctation similar to that of head; rows of coarse setigerous punctures present along anterior margin, close to lateral sides, several punctures present also in shallow basolateral depressions along basal margin. Pronotum baso-laterally with several longitudinal strioles. Centre of disc with indistinct median longitudinal smooth line.

Scutellum transversely triangular.

Elytra. Base of elytra as broad as pronotal base; lateral margins of elytra slightly diverging in basal third, then distinctly narrowing to apex. Four shallowly impressed and fragmented dorsal striae present on each elytron: all striae beginning posterior to base; stria 1 shortest, ending at two thirds of elytral length; striae 2–3 longer, ending at three fourths of elytral length; stria 4 beginning more closely to base, apically fragmented, ending at second third of elytral length. Submarginal stria absent. Reticulation similar to that of head and pronotum, but less impressed. Punctation consisting of coarse setigerous punctures and very fine sparse punctures; coarse punctures present along elytral striae and lateral margins of elytra.

Legs. Protibia broadened anteriorly, club shaped. Pro- and mesotarsomeres 1–3 distinctly broadened, with rows of adhesive setae on their ventral side; posterior (outer) protarsal claw shorter and more curved than anterior claw.

Ventral surface. Prosternum sinuate anteriorly, obtusely keeled medially. Prosternal process shortly lanceolate, in cross-section convex, apex obtuse; process distinctly bordered laterally; reticulation imperceptible. Metaventrite with reticulation consisting of transverse 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 a few long transverse and numerous shorter longitudinal strioles; reticulation consisting of elongate, longitudinal 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 antero-medially on ventrites III–V; ventrite VI with setigerous punctures laterally on either side. 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 in lateral view sickle-shaped, broadest at mid-length, tapering continuously to dorsally bent truncate apex ( Fig. 5a ); in ventral view, tapering to left-curved obtusely pointed apex ( Fig. 5b ); ventral lobe closely pressed from left side to dorsal lobe in ventral view ( Fig. 5b ). Paramere triangular; basal two thirds broad, laterally rounded; distal third slender, with indistinct setation on medial margin; apical lobes club-shaped ( Fig. 6 ).

Female. Unknown.

Variability. Both specimens of the type series are rather uniform in habitus, reticulation and colouration. They differ slightly in elytral striation – striae are more fragmented in paratype specimen; minor variability can be seen also in shape and size of yellow elytral markings.

Measurements. TL: holotype: 4.3 mm; paratype: 4.2 mm. TL-h: holotype: 3.8 mm; paratype: 3.7 mm. MW: holotype and paratype: 1.85 mm.

Differential diagnosis. The new species can be easily recognised from all other Austrelatus by the combination of small body length, disc of elytra with four longitudinal striae ( Fig. 2 ) and the shape of male genitalia ( Fig. 5 ). It is most similar to Sino-Japanese A. parallelus (Zimmermann, 1920) (see JIANG et al. 2023), but their relationships are presently not clear.

Etymology. The new species is dedicated to the late Ignacio Ribera (1963–2020), renowned specialist on aquatic beetles; the specific epithet is a noun in the genitive case. Collecting circumstances. The Mintaingbin Forest Camp specimen was among the beetles collected from a deep pool between limestone rocks (size ca. 5 × 3 m, steep banks, water transparent, bottom of limestone gravel covered with leaf litter), small, shallow puddles with leaf litter near it and from the ground among leaf litter in the forest close to a stream, at the altitude ca. 1250 m. The Inle Lake specimen was collected at light.

Distribution. Austrelatus riberai sp. nov. is so far known only from two close localities (situated ca. 55 km apart) in Shan State, central Myanmar.

Figures

Figs 1–6. 1–2 – habitus of Austrelatus holotypes: 1 – A. mirai sp. nov.; 2 – A. riberai sp. nov. 3–6 – male genitalia of Austrelatus: 3–4 – A. mirai sp. nov.; 5–6 – A. riberai sp. nov. 3, 5 – median lobe in lateral (a) and ventral (b) view; 4, 6 – parameres. Scale bar = 0.5 mm (Figs 3–6).