Copelatus bougainvillensis, Hájek & Shaverdo & Hendrich & Balke, 2021

Hajek, Jiri, Shaverdo, Helena, Hendrich, Lars & Balke, Michael, 2021, A review of Copelatus diving beetles from the Solomon Islands, reporting the discovery of six new species (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 1023, pp. 81-118 : 81

Copelatus bougainvillensis sp. nov. Figures 2 , 16

Type locality.

Papua New Guinea: Autonomous Region of Bougainville, Kieta .

Type material.

Holotype: ♂, labelled: " Papua New Guinea: Bougainville, / Kieta , 620 m, 16.vi.2008, 06.13.035S / 155.30.401E, Posman, (PNG179a) [p] // HOLOTYPE ♂ / COPELATUS / Copelatus bougainvillensis sp. nov. / Hájek, Shaverdo, Hendrich & Balke det. 2020 [red label, p]" ( ZSMG) .

Paratypes: 20 ♂♂, 15 ♀♀, same data as holotype ( NHMUK, NHMW, NMPC, ZSMG) .

Description of male holotype.

Habitus: Elongate, oblong-oval, broadest before mid-length of elytra; body moderately convex in lateral view. Body outline continuous, with only indistinct discontinuity between pronotum and elytra. Dorsal surface shiny (Fig. 2 ).

Colouration: Body colour ferruginous; head on vertex, disc of pronotum, elytra along striae, and metaventrite darkened, brown blackish.

Head: Moderately broad, ca. 0.64 × width of pronotum, trapezoidal. 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 very small punctures spread sparsely on surface; row of coarse punctures present around inner margin of eyes, several punctures present at frontal level of eyes, and anterolaterally to eyes in fronto-clypeal depressions.

Pronotum: Transverse (width/length ratio = 2.50), broadest between posterior angles; lateral margins almost straight in basal two thirds, slightly curved in anterior third. Sides with lateral beading very thin but distinct, except for anterior angles. Reticulation similar to that of head. Punctation similar to that of head; rows of coarse setigerous punctures present along anterior margin, laterally in longitudinal depression close to sides, several punctures present also in basolateral depressions along basal margin. Disc of pronotum laterally with few short, irregularly distributed longitudinal strioles; several strioles present also in depressions close to posterior angles. Centre of disc with medial longitudinal smooth line.

Elytra: Base of elytra as broad as pronotal base; lateral margins of elytra slightly diverging in basal third, distinctly narrowing in apical half. Eleven discal and a submarginal longitudinal striae present on each elytron: stria 1 beginning posterior from scutellum; striae 2, 4, 6, 8 complete; striae 3, 5, 7, 9, 10 absent at base; stria 9 and 10 somewhat fragmented basally; all odd striae generally shortened apically. Submarginal stria present only as few short striolae in two thirds of elytral length. Surface reticulation similar to that of head and pronotum, meshes slightly smaller and less impressed. Punctation double, consisting of row of coarse setigerous punctures along elytral striae 4, 6, 8 and along lateral margin of elytra, and very fine sparsely distributed punctures.

Legs: Protibia simple, slightly broadened anteriorly, club shaped. Pro- and mesotarsomeres 1-3 distinctly broadened, with adhesive setae on their ventral side. Anterior protarsal claw broad basally, slightly constricted in apical third, strongly curved.

Ventral side: Prosternum sinuate anteriorly, obtusely keeled medially. Prosternal process shortly lanceolate, in cross-section convex, apex obtuse; process distinctly bordered laterally; reticulation consisting of shallow, hardly perceptible polygonal meshes. Metaventrite with microsculpture consisting of polygonal meshes; lateral parts of metaventrite ("metasternal wings") tongue-shaped, slender. Metacoxal lines well impressed, nearly complete, absent only close to metaventrite. Metacoxal plates covered with long, deep longitudinal strioles; reticulation consisting of elongated, longitudinal polygonal meshes. Metacoxal processes rounded and indistinctly incised at posterior margin. Abdominal ventrites I-II with longitudinal strioles; ventrites III and 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 and II, oblique on ventrite III and transverse on ventrites IV-VI. Punctation consisting of fine, sparsely distributed punctures; punctures coarser and denser laterally on apical ventrite.

Genitalia: Median lobe of aedeagus (Fig. 16 ) sickle-shaped, with pointed apex and distinct rugose surface sculpture visible in lateral view (Fig. 16A, B ); consisting of dorsal and ventral sclerites; dorsal sclerite divided into two parts of different shape in apical half, left part with lateral margin slightly curved and apex pointed (Fig. 16C ); ventral sclerite with left part strongly sclerotised, its apex in shape of a small hook visible in lateral left view (Fig. 16B ), right part membranous; apexes of dorsal and ventral sclerites elongate, more or less pressed together.

Lateral lobes (parameres) of narrow triangular form, with almost straight setigerous dorsal margin; setae numerous, dense, and strong distally, and distinctly less numerous, weaker, and sparser basally (Fig. 16D ).

Female. Identical to male in habitus. Pro- and mesotarsomeres not broadened, without adhesive setae; protarsal claws simple.

Variability.

The specimens of the type series vary in extent of infuscation of the pronotal disc and elytra; in some specimens, the pronotum is largely brown blackish with ferruginous sides, and the centre of elytral disc is almost uniformly brown blackish. There is also a variation in number and position of longitudinal strioles on pronotum. Finally, there is a little variability in elytral striation: striae 2-9 may all beginning at the base of elytra, but also the odd striae 3, 5, 7, 9 may be fragmented at the base of elytra.

Measurements.

TL: 5.2-5.7 mm (mean value: 5.5 ± 0.1 mm); holotype: 5.2 mm. TL-h: 4.7-5.2 mm (mean value: 5.0 ± 0.1 mm); holotype: 4.7 mm. MW: 2.4-2.7 mm (mean value: 2.6 ± 0.1 mm); holotype: 2.5 mm.

Differential diagnosis.

Based on the presence of eleven dorsal striae and a submarginal stria, the new species can be classified within C. trilobatus species group, see under C. baranensis sp. nov. Copelatus bougainvillensis sp. nov. differs from all species of the C. trilobatus group by combination of small body length, dorsal surface colouration and the shape of the male genitalia.

On the other hand, in general appearance and structure of the male genitalia, Copelatus bougainvillensis sp. nov. is very similar (and probably closely related) to C. baranensis sp. nov. It can be distinguished from the latter species by habitus with pronotal sides almost straight in basal two thirds, and elytra diverging in basal third (not subparallel), and by median lobe apically more elongate and more slender, with apex differently shaped (cf. Figs 15 , 16 ). For differentiation from sympatric C. kietensis sp. nov., see below.

Etymology.

The species is named after the Bougainville Island where it was collected. The specific epithet is an adjective in the nominative singular.

Distribution.

The species is to date only known from the type locality on the eastern coast of the Bougainville Island .

Habitat.

Unknown.

Figures

Figure 15. Male genitalia of Copelatus baranensis sp. nov. (holotype) A median lobe in lateral view, right side B median lobe in lateral view, left side C median lobe in ventral view D left paramere in external view. Scale bar: 0.5 mm.

Figure 16. Male genitalia of Copelatus bougainvillensis sp. nov. (holotype) A median lobe in lateral view, right side B median lobe in lateral view, left side C median lobe in ventral view D left paramere in external view. Scale bar: 0.5 mm.

Figures 1, 2. Habitus of Copelatus 1 C. baranensis sp. nov. (holotype; TL: 5.9 mm) 2 C. bougainvillensis sp. nov. (holotype; TL: 5.2 mm).