Platynectes popomanaseu, Hájek & Šťastný & Hendrich & Balke, 2023

Hájek, Jiří, Šťastný, Jaroslav, Hendrich, Lars & Balke, Michael, 2023, A review of the genus Platynectes from the Solomon Islands (Coleoptera: Dytiscidae: Agabinae), Acta Entomologica Musei Nationalis Pragae 63 (1), pp. 57-74 : 68-70

Platynectes popomanaseu sp. nov.

( Figs 7 , 15 )

Type locality. Solomon Islands, Guadalcanal, Mount Popomanaseu, ca. 9°42.2′S, 160°03.7′E.

Type material. HOLOTYPE: J ( BMNH), labelled: ‘SOLOMON IS: [red underlined] / Pres./ P.J.M.Greenslade./ B.M.1966-477.[p] // SOLOMON IS. / Guadalcanal [p] / Popamanasiu />7000′ [hw] / 22/10 [hw] 196 [p] 5 [hw] / 20063.[hw] / P.Greenslade [p] // HOLOTYPEJ / PLATYNECTES / popomanaseu sp. nov. / J. Hájek et al. det. 2021 [p, red label]’. PARA- TYPE: 1♀, same label data as holotype [pinned on same card as holotype] ( BMNH). The paratype with the respective red printed label.

Description. Male holotype. Habitus. Broadest before elytral midlength; body outline discontinuous, base of pronotum narrower than base of elytra.

Colouration ( Fig. 7 ). Surface dark brown. Head with orange-brown clypeus, indistinct reddish-brown spot medially on frons and two spots on vertex; appendages orange. Pronotum with broadly orange sides; basal and anterior margins indistinctly paler, reddish-brown; with two indistinct reddish-brown spots on disc. Scutellum reddish-brown. Elytron with indistinct reddish-brown stripe along suture; sides light brown; epipleura orange-brown; elytral markings consisting of thin sublateral longitudinal yellow line in apical half, line almost interrupted subapically and then broadened to triangular subapical spot. Legs orange-brown. Ventral surface with orange-brown prosternum, including prosternal process; metaventrite indistinctly paler, reddish-brown; metacoxal processes orange-brown; abdominal ventrites indistinctly paler laterally, apical ventrite orange-brown medio-posteriorly.

Head ca. 0.65× width of pronotum, transversely elliptical. Meshes of reticulation often incomplete (not closed).

Pronotum. Reticulation similar to that of head, meshes often incomplete; meshes finer and less impressed on disc, becoming larger and deeply impressed near sides. Microreticulation absent. Centre of pronotal disc with small indistinct longitudinal furrow.

Elytra. Punctation double; coarse punctures present in two discal and two lateral relatively distinct longitudinal lines, few punctures present also along suture; fine punctures distributed irregularly over elytral surface, occurring mostly in intersections of reticulation. Reticulation similar to that of head and pronotum but slightly less impressed, consisting of heterogeneous polygonal meshes; meshes often incomplete. Microreticulation absent.

Ventral surface. Medial part of metaventrite with sparse fine punctation. Ratio WC/WS = 4.80. Metacoxal lines incomplete anteriorly, almost parallel-sided. Metacoxal plates reticulated with polygonal meshes, punctation consisting of sparse fine punctures. Abdominal ventrites with bunch of coarse setigerous punctures present in centre of ventrites III–V, additional setigerous punctures arranged sparsely in transverse line in medial part of ventrites.

Male genitalia. Median lobe ( Fig. 15a ) in lateral aspect slender in median part; apex expanded, broadly rounded with subapical notch on dorsal side, distinctly setose on ventral side. Parameres ( Fig. 15b ) narrowly triangular, slender, deeply incised basally; dorsal surface densely setated; apical lobe very long.

Female. Identical to male in habitus.

Measurements. (N = 2). TL: J = 6.30 mm; ♀ = 6.20 mm. Tl-h: J ♀ = 5.50 mm. MW: J = 3.40 mm; ♀ = 3.50 mm.

Differential diagnosis. The new species can be recognized from all other Platynectes from the Solomon Islands by combination of small body size, elongate habitus with discontinuous body outline, dorsal surface pattern ( Fig. 7 ) and the shape of male genitalia ( Fig. 15 ).

Etymology. The new species is named after its area of occurrence – volcano Mount Popomanaseu, the highest place on the Guadalcanal Island. The specific epithet is a noun in the nominative singular, standing in apposition.

Collecting circumstances. Unknown.

Distribution. The new species is so far known only from the type locality, Mount Popomanaseu in south-central Guadalcanal ( Fig. 25A ).

Platynectes insularis

J. Balfour-Browne, 1939, status reinstituted

( Figs 16–21 )

Platynectes insularis J. Balfour-Browne, 1939: 466 . Platynectes insularis ab. semilineatus Guignot, 1939: 180 (unavailable name). Platynectes semperi Régimbart, 1899 : GUḖORGUIEV (1972): 53 (partim).

Type locality. ‘Banks Islands: Vanua Lava’ [ Vanuatu: Torba Province]. Type material. HOLOTYPE J ( BMNH),labelled:‘Holo [hw] / Type [p] /J [hw] [round label with red frame] // New Hebrides: [orange underlined] / Banks Is. / Vanua Lava. / x.1929. / L.E.Cheesman. / B.M. 1930-477. [p] // Platynectes / insularis Type![hw] / J.Balfour-Browne det. [p]’. PARATYPES: 1 ♀, labelled: ‘Allo [hw] / Type [p] / ♀ [hw] [round label with red frame] // New Hebrides: [orange underlined] / Banks Is. / Vanua Lava. / x.1929. / L.E.Cheesman. / B.M. 1930-477. [p] // Platynectes / insularis n. sp. [hw] / J.Balfour-Browne det. [p]’; 9 JJ 5 ♀♀, same locality label data as holotype, but ‘Para- / type [p, round label with yellow frame]’, one male with additional label ‘ Platynectes / insularis m. [hw] / J.Balfour-Browne det. [p]’; 5 JJ 3♀♀, labelled:‘Para- / type [p, round label with yellow frame] // New Hebrides:[orange underlined] / Aneityum. / xi.1930. / L.E.Cheeseman. / B.M.1931-141. [p]’, one male with additional label ‘ Platynectes / insularis m. [hw] / J.Balfour-Browne det. [p]’; 1 ♀, labelled: ‘Para- / type [p, round label with yellow frame] // New Hebrides: [orange underlined] / Erromanga. / vii.1930. / L.E.Cheeseman. / B.M.1930-477. [p]’; 2 JJ, labelled: ‘Para- / type [p, round label with yellow frame] // New Hebrides: [orange underlined] / Malekula. / Malua Bay. / vi.1929. / L.E.Cheeseman. / B.M.1929-410. [p]’; 1 ♀, labelled: ‘Para- / type [p, round label with yellow frame] // New Hebrides: [orange underlined] / Tanna. / x.1930. / L.E.Cheeseman. / B.M.1931-141. [p]’ (all BMNH).

Additional material examined. VANUATU: AMBRYM: Mts., Marum et Bembow, 1935-1936 E. Aubert de la Rue, PARATYPE, Platynectes insularis Balf.Br. ab. semilineatus Guignot, 1J 1♀ ( MNHN). ANEITYUM: 3 m. NE ofAnelgauhat,Red Crest, 1,200 ft., iii.1955, L.E.Cheesman coll., 1 J 2♀♀ ( BMNH). ESඉIRITU SANTO: Penaorou, xi.2006, IBISCA SANTO Project, J. Schmidl leg., 1 J ( ZSMG); SW Manatagopa, 300 m, 28.viii. 1957, J.L. Gressitt leg., 3 JJ 1 ♀ ( BMNH). TANNA: Lenakel, 100-200 m, in small puddle – road, 29.i.1981, N.L.H. Krauss leg., 1 ♀ ( BMNH).

Diagnosis. Small species. Rather variable in dorsal colouration: Typical specimens with round orange spot between eyes and two transverse spots on vertex; pronotum with lateral side and anterior corners broadly orange; elytron with transverse postmedian yellow-orange spot, two short longitudinal lines in apical third of elytron, and lateral band beginning before elytral midlength ( Fig. 16 ). However, in some specimens, lines in apical third of elytron may be prolonged (ab. semilineatus), confluent into transverse spot, lateral band may be extended to basal third of elytron, or, on the other hand, spots on elytron may be absent and only lateral band is present. Reticulation consisting of heterogeneous polygonal meshes, meshes mostly complete (closed); fine punctures presenting both on lines of reticulation and inside meshes. Traces of microreticulation perceptible laterally and in apical third of elytra. Prosternal column steep, almost roof-shaped; prosternal process broadly lanceolate, in cross-section slightly convex; distinctly bordered in basal half, apex pointed. Ratio WC/ WS = 4.30. Metacoxal lines incomplete anteriorly, slightly divergent. Median lobe ( Figs 18a, 19–21 ) in lateral aspect simple, sickle-shaped, slender in median part and slightly broadened in apical third; apex broadly rounded, distinctly setose on ventral side. Parameres ( Figs 17b ) narrowly triangular, slender, incised basally; dorsal surface densely setated; apical lobe long.

Measurements (N = 20). TL: 4.95–5.90 mm (mean value: 5.45 ± 0.20 mm). Tl-h: 4.30–5.30 mm (mean value: 4.85 ± 0.20 mm). MW: 2.55–3.15 mm (mean value: 2.90 ± 0.15 mm). Notes. BALFOUR- BROWNE (1939) stated the measurements (based on the same specimens) incorrectly as TL: 5.91–6.27 mm (mean value: 6.09); MW: 3.0– 3.36 mm (mean value: 3.18 mm).

Comments on classification. GUḖORGUIEV (1972) synonymised P. insularis with P. semperi Régimbart, 1899 , without providing any detailed information. The identity of P. semperi is unclear as the syntype series contains specimens from the Philippines, Indonesian Sulawesi and New Guinea (RḖGIMBART 1899), and probably represent several species. So far a lectotype for this taxon was not designated. On the other hand, based on a molecular analysis by TOUSSAINT et al. (2017: Fig. 2 ), P. insularis is closely related to species from Solomon Islands and differs significantly in COI sequence from taxa from the Philippines, Sunda Islands or New Guinea. Therefore, we reinstituted Platynectes insularis J. Balfour-Browne, 1939 here as a valid species. Platynectes insularis differs from all Solomon Islands’ species, but P. owaraha sp. nov., in smaller body length and colouration of dorsal surface. For separation of P. insularis and P. owaraha sp. nov. see under the latter species.

Platynectes insularis in current concept is rather widespread and morphologically variable species. There are differences between populations in both, dorsal colouration ( Figs 16–17 ) and the shape of the male genitalia ( Figs 18–21 ). However, we were not able to find any constant pattern in colouration, while the differences in the shape of the median lobes may be (at least partially) artificial due to incomplete unfolding of median lobe of very old specimens during moistening process in KOH and glycerine. Additional, especially DNA grade material is necessary to answer the question whether P. insularis represent one variable species or a complex of species occurring on particular islands. The paratype specimens from Santa Ana ( Solomon Islands, Owaraha) were recognised as a distinct species different from P. insularis (see under P. owaraha sp. nov.). Collecting circumstances. Unknown.

Distribution. Vanuatu (Ambrym, Aneityum, Erromango, Espiritu Santo, Malakula, Tanna, Vanua Lava) ( Fig. 25B ).

Figures

Fig 7. Habitus of Platynectes popomanaseu sp. nov. in dorsal (a) and frontolateral (b) view.

Figs 12–15. Male genitalia of Platynectes. 12 – P. mbaole sp. nov. (holotype); 13 – P. mbaole sp. nov. (paratype, Sutakiki); 14 – P. owaraha sp. nov.; 15 – P. popomanaseu sp. nov. a – median lobe in lateral view; b – parameres. Scale bar = 0.5 mm.

Fig. 25. Distribution of Platynectes species in the Solomon Islands (A) and Vanuatu (B).

Figs 16–21. Platynectes insularis J. Balfour-Browne, 1939. 16 – paratype (Vanua Lava); 17 – ab. semilineatus (Ambrym); 18 – holotype (Vanua Lava); 19 – ab. semilineatus (Ambrym); 20 – paratype (Aneityum); 21 – paratype (Malekula). 16–17 – Habitus in dorsal (a) and frontolateral (b) view. 18–21 – Male genitalia: a – median lobe in lateral view; b – parameres. Scale bar = 0.5 mm.

Figs 1–3. Habitus of Platynectes in dorsal (a) and frontolateral (b) view. 1 – P. barana sp. nov.; 2 – P. lunga sp. nov.; 3 – P. makira sp. nov. Not to scale.