Copelatus laevipennis, 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 laevipennis sp. nov. Figures 4 , 18 , 23

Type locality.

Solomon Islands, Guadalcanal , 0.5 km N of Mbaole Village , 09°37.69'S, 160°06.69'E .

Type material.

Holotype: ♂, labelled: " Salomonen: C- Guadalcanal , / 0.5 km N Mbaole , 2799 feet / S 09°37.69 E 160°06.69E / 2007 K. Mailautoka leg. [p] // DNA / M. Balke / 2907 [green label, p] // HOLOTYPE ♂ / COPELATUS / Copelatus laevipennis sp. nov. / Hájek, Shaverdo, Hendrich & Balke det. 2020 [red label, p]" ( ZSMG) .

Paratypes: 1 ♂, same locality data as holotype, with additional label: "DNA / M. Balke / 3334 [green label, p]" ( NMPC) ; 2 ♀♀, labelled: " Solomon Islands: C- Guadalcanal , / 0.5 km N Mbaole , 853 m, 2007, / 09°37.69S, 160°06.88E, K. Mailautoka [p]" ( NMPC, ZSMG) ; 10 ♂♂, 7 ♀♀, labelled: "SOLOMON IS.: / Guadalcanal Is. / Suta / 27.vi.1956 [p] // E.S.Brown / B.M.1957-201 [p]" ( NHMUK, NMPC, ZSMG) ; 1 ♂, labelled: "5327 [on side, hw] / SOLOMON IS. [red underlined] / Guadalcanal [p] / Suta / 27.vi. [hw] 195 [p] 6 [hw] / E.S.Brown [p] / Sangava / R [on reverse, hw] // E.S.BROWN coll / C.I.E. 1957-24 [hw] // E.S.Brown / B.M.1957-201 [p]" ( NHMUK) ; 1 ♂, labelled: " ♂ [p] // Type [round label with red frame, p] // SOLOMON IS: / GUADALCANAL / Tenaru R. headwaters. / 1820' 5.viii.53. / In hole in tree trunk. [hw] // Brit.Mus. / 1987-14 [p] // aC 2 [hw] // Copelatus / torosus Type! [hw] / J. Balfour-Browne det., 195 [p] 3 [hw]" ( NHMUK) . All paratypes with the respective printed red label .

Description of male holotype.

Habitus: Elongate, oblong-oval, broadest shortly before mid-length of elytra; body distinctly convex in lateral view. Body outline continuous, without discontinuity between pronotum and elytra. Dorsal surface shiny (Fig. 4 ).

Colouration: Body colour pitchy brown; sides of pronotum (except for lateral margin) and appendages paler, ferruginous.

Head: Moderately broad, ca. 0.65 × width of pronotum, trapezoidal. Anterior margin of clypeus indistinctly concave. Antenna with antennomeres long and slender. Reticulation consisting of moderately deeply impressed 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, few punctures present at frontal level of eyes, and several punctures anterolaterally to eyes in fronto-clypeal depressions.

Pronotum: Transverse (width/length ratio = 2.78), broadest between posterior angles, lateral margins moderately curved. Sides with lateral 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, laterally in longitudinal depression close to sides, several punctures present also in basolateral depressions along basal margin. Disc of pronotum with shallow medial longitudinal scratch.

Elytra: Base of elytra as broad as pronotal base; lateral margins of elytra subparallel-sided in basal half, distinctly narrowing in apical half. Elytral striae absent. Reticulation similar to that of head and pronotum, meshes somewhat elongated longitudinally. Punctation consisting of coarse setigerous punctures and very fine sparse punctures. Coarse punctures arranged in three distinct longitudinal puncture lines: two discal and one lateral; another row of punctures present along lateral margin of elytra, and few coarse punctures present also in interspace between discal and lateral puncture lines.

Legs: Protibia modified, angled near base, distinctly broadened anteriorly, club shaped. Pro- and mesotarsomeres 1-3 distinctly broadened, with adhesive setae on their ventral side.

Ventral side: Prosternum sinuate anteriorly, obtusely keeled medially. Prosternal process shortly lanceolate, in cross-section convex, apex obtuse; process distinctly bordered laterally; reticulation almost effaced. 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 laterally with long, deep longitudinal strioles; reticulation consisting of extremely elongated, longitudinal polygonal meshes. Metacoxal processes rounded and incised at posterior margin. Abdominal ventrites I and 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.

Genitalia: Median lobe of aedeagus (Fig. 18 ) sickle-shaped, with evident dorsal and ventral sclerites; dorsal sclerite without surface sculpture and divided into two parts in apical half: left part shorter than right one, both slightly curved, with small crests, notches and truncate apexes (Fig. 18A, B ); ventral sclerite divided into two parts apically: left part more strongly sclerotised, broader, shorter, with broadly pointed apex, right part longer, partly sclerotised (medially membranous), with elongate, thin apex in shape of very weak hook (Fig. 18C ).

Lateral lobes (parameres) of narrow triangular form, with broader subdistal part due to curved setigerous dorsal margin; setae numerous, dense, and strong distally, and distinctly less numerous, weaker, and sparser basally (Fig. 18D ).

Female. Identical to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro- and mesotarsomeres not broadened, without adhesive setae.

Variability.

All specimens of the type series agree well with the holotype. There is only slight variability in body colouration: some specimens have head with pale frontal part and dark vertex, and the sides of elytra are indistinctly paler than elytral disc. Few longitudinal strioles present in depression close to posterior angles of pronotum in one female. Small differences were detected also in the shape of the male median lobe: a notch on right part of dorsal sclerite can be almost absent in some specimens (cf. Figs 18B , 23 ).

Measurements.

TL: 6.3-7.2 mm (mean value: 6.9 ± 0.2 mm); holotype: 6.9 mm. TL-h: 5.7-6.4 mm (mean value: 6.2 ± 0.2 mm); holotype: 6.3 mm. MW: 3.2-3.6 mm (mean value: 3.4 ± 0.1 mm); holotype: 3.4 mm.

Differential diagnosis.

Based on the absence of elytral striae, the new species can be included into the C. hydroporoides species group (or haemorrhoidalis, in earlier studies). This species group contains currently 55 species distributed predominantly in Afrotropical and Neotropical regions ( Nilsson and Hájek 2020). Only two species of this group were recently described from the Oriental (Maluku, Indonesia) and Australian regions ( Papua New Guinea) by Hájek et al. (2010) and Megna et al. (2017), respectively.

Based on shape of the median lobe and paramere, C. laevipennis sp. nov. is without any doubt closely related to C. variistriatus sp. nov., which it resembles also in size, body shape, and colouration, and C. urceolus sp. nov. The type localities of C. laevipennis sp. nov. and C. variistriatus sp. nov. are only ca. 20 km apart, although they differ significantly in altitude. Due to great variability of elytral striation in C. variistriatus sp. nov. described below, we hesitated first to describe another species, which may represent only a non-striated population of one species. Finally, we have decided to describe both species, because of: 1) C. laevipennis sp. nov. has more parallel habitus than C. variistriatus sp. nov.; 2) there are no intermediate specimens, i.e., there are no specimens of C. variistriatus sp. nov. without elytral striae, and no specimens of C. laevipennis sp. nov. with traces of striae; 3) minor differences in the shape of the median lobe can be detected between both species, mainly in shape of the apexes of parts of the dorsal and ventral sclerites (cf. Figs 18 , 22 - 25 ); 4) there is significant genetic divergence between both species: uncorrected genetic distances between the sequenced CO1 haplotypes of C. laevipennis sp. nov. and C. variistriatus sp. nov. are ca. 7% (pers. obs.).

Etymology.

The species name is composed from Latin adjective laevis (- is, - e, = smooth) and noun penna (- ae, feminine, = wing), referring to smooth elytra without striae.

Distribution.

The species is known only from medium altitude area (ca. 600-900 m) in north-central Guadalcanal .

Habitat.

Largely unknown; according to label data, one specimen was collected in a water-filled hole in tree trunk.

Figures

Figure 18. Male genitalia of Copelatus laevipennis 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 22. Male genitalia of Copelatus variistriatus 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 3, 4. Habitus of Copelatus 3 C. kietensis sp. nov. (holotype; TL: 6.3 mm) 4 C. laevipennis sp. nov. (holotype; TL: 6.9 mm).

Figures 23 - 25. Variability of Copelatus male genitalia: median lobe in lateral view, left side 23 Copelatus laevipennis sp. nov. (paratype) 24, 25 C. variistriatus sp. nov. (paratypes). Scale bar: 0.5 mm.