Platynectes barana, 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 : 58-62

Platynectes barana sp. nov.

( Figs 1 , 8 )

Type locality. Solomon Islands, Guadalcanal, 3.5 km SE of Barana vill. Type material. HOLOTYPE: J ( NMPC), labelled: ‘ SOLOMON ISLANDS, GUADALCANAL / ca. 3.5 km SE of BARANA vill. / (drying up stream in shaded gorge) / 09°29.8′S, 159°59.5′E; 190 m / Jiří Hájek leg., 24.xi.- 14.xii.2013 [p] // HOLOTYPE J / PLATYNECTES / barana sp. nov. / J. Hájek et al. det. 2021 [p, red label]’. PARATYPES: 19 JJ 18 ♀♀, same label data as holotype but two specimens with ‘DNA M. Balke 6320 and 6321’[p, white label] ( BPBM, JSCL, NMPC, ZSMG); 1J 2♀♀, labelled: ‘ SOLOMON ISLANDS, GUADALCANAL / Mt.Austine - BARANA vill.env. / (secondary forest, gardens, stream) / 09°28.0′S, 159°58.4′E; 280 m / Jiří Hájek leg., 23.xi.-8.xii.2013 [p]’ ( NMPC); 2 ♀♀, labelled: ‘ SOLOMON ISLANDS, GUADALCANAL / LUNGA river env., Honiara reg. / 5-15km S of Barana vill. / 50-100 m, 22.xi.-18.xii.2016 / St. Jákl leg.’ ( NMPC); 1 ♀, labelled: ‘ SOLOMON ISLANDS, GUADALCANAL / Koso vill. env. / 15-18km SSE of Honiara / 500-650 m, 1.-18.xii.2016 / St. Jákl leg.’ ( NMPC); 34JJ 28♀♀, labelled: ‘ Solomon Islands / GUADALCANAL I., Honiara reg. / Barana vill. env. 100-300 / XI-XII.2018 / St. Jakl leg. / Coll. Hendrich’ ( LHCM, NMPC, ZSMG); 10 JJ 4 ♀♀, labelled: ‘from / small stream [hw] // SOLOMON IS.: [red underlined] / Guadalcanal I. / Tapenanje. c. 1,100 ft. / 21-23.xii.1953. / J.D.Bradley [p] // RENNEL I. / Expedition./ B.M.1954-222 [p]’ ( BMNH); 8JJ 6♀♀, with same label data, but locality label handwritten ( BMNH); 1♀, labelled:‘swift stream [hw] // SOLOMON ISLANDS [red underlined] / GUADALCANAL / MONITEZ CREEK / 3.VII.1965 / P.N.LAWRENCE [hw]’ ( BMNH); 1 J 1 ♀, labelled: ʻSalomonen: C-Guadalcanal, / 0.5 km N Mbaole, 2799 feet / S 09°37.69 E 160°06.69E / 2007 K. Mailautoka leg. [p]’, both specimens with additional label: ‘DNA / M. Balke / 3335 [2908 respectively] [p, green label]’ ( ZSMG); 5 JJ 6 ♀♀, labelled: ʻSOLOMON IS. / Guadalcanal / Betikama R. / VIII.1960 // W.W. Brandt collector / Bishop[p]’ ( BPBM).All paratypes with the respective red printed label.

Description. Male holotype. Habitus ( Fig. 1 ) elongate oblong oval, broadest in one third of elytral length, dorsally convex; body outline continuous, without angle between base of pronotum and elytra. Dorsal surface shiny.

Colouration. Surface black. Head with orange-brown clypeus, big round orange spot medially on frons and two small spots on vertex; appendages orange-brown. Pronotum with narrowly orange-brown sides and large triangular orange spot antero-laterally; basal margin somewhat reddish translucent. Scutellum black. Elytron black with brownish lateral margin and epipleura, disc with distinct yellowish pattern consisting of subbasal transverse band, two postmedial spots in two thirds of elytral length, and one subapical spot; subbasal band reaching neither lateral margin nor suture, broadest in lateral half, narrowed in medial half, slightly concave on its posterior margins; lateral postmedial spot transverse, medial spot round; preapical spot roundish, trace of thin line connecting lateral postmedial and preapical spot perceptible. Legs orange-brown. Ventral surface brown-blackish, median part of metacoxae and metacoxal processes reddish-brown; abdominal ventrites II–IV with orange-brown spots laterally.

Head. Moderately broad, ca. 0.58× width of pronotum, transversely elliptical. Anterior margin of clypeus truncate. Antennae with antennomeres elongate; club-shaped. Eyes emarginate anterolaterally. Punctation double; several large setigerous punctures present in fronto-clypeal grooves, in depressions on frons, and in rows along eyes; fine punctures distributed sparsely and irregularly on head surface, mostly on lines of reticulation. Reticulation consisting of heterogeneous polygonal meshes, meshes mostly incomplete (not closed); reticulation absent anteriorly on clypeus. Microreticulation (i.e. secondary reticulation inside meshes) absent.

Pronotum. Transverse, broadest at posterior angles. Both anterior and posterior angles acute. Sides slightly and evenly curved, with distinct, broad lateral beading except for anterior angles. Anterior margin straight, posterior margin slightly sinuate. Punctation double, similar to that of head; row of coarse setigerous punctures present along anterior and basal margin (except for medially); fine punctures distributed irregularly on pronotal surface, present mostly on lines of reticulation. Reticulation similar to that of head, consisting of heterogeneous polygonal meshes; reticulation reduced in centre of disc, meshes larger, incomplete and less impressed on disc, becoming smaller, closed and deeply impressed near sides. Microreticulation absent. Centre of pronotal disc with small fossa.

Scutellum broadly triangular.

Elytra with sides evenly rounded, lateral margin bordered. Punctation double; coarse punctures present in two discal and a lateral relatively distinct longitudinal lines, few punctures present also along suture and lateral margin; fine punctures distributed irregularly over elytral surface, occurring mostly on lines of reticulation. Reticulation similar to that of head and pronotum but slightly less impressed, consisting of heterogeneous polygonal meshes; meshes often incomplete. Traces of microreticulation hardly perceptible in apical half of elytra.

Legs. Meso- and metafemora with bunch of spiniform setae along posterolateral margin. Pro- and mesotibia club shaped, densely punctured with spiniferous punctures over ventral surface. Metatibia with two lines of coarse spiniferous punctures over ventral surface. Pro- and mesotarsomeres 1–3 moderately dilated, ventrally with adhesive setae. Pro- and mesotarsal claws simple, evenly curved; anterior claw longer and less curved than posteri- or one. Metatarsal claws subequal; anterior (outer) claw longer, thicker and more straight than posterior (inner) one. Surface of legs with distinct reticulation consisting of elongate oblique or transverse meshes. Elongate natatorial setae present in lesser extent on dorsal surface or pro- and mesotarsomeres 1–3, and in high number on dorsal margin of meso- and metatibiae, as well as on both, dorsal and ventral margin of metatarsomeres.

Ventral surface. Genae reticulated with polygonal meshes. Prosternum sinuate anteriorly, obtusely keeled medially. Lateral portions of prosternum rugosely punctate, with transverse reticulation. Prosternal column with sparse fine punctation. Prosternal process broadly lanceolate, in cross-section slightly convex; distinctly bordered in basal half, apex pointed; surface with irregular sparse double punctation. Medial part of metaventrite without microsculpture, shiny, with sparse fine punctation; lateral parts of metaventrite (‘metasternal wings’) slender, tongue-shaped, transversely reticulated. Ratio WC/WS = 5.0. Metacoxal lines well impressed, incomplete anteriorly, almost parallel-sided. Metacoxal plates reticulated with polygonal meshes, punctation consisting of sparse fine punctures. Abdominal ventrites I–V with reticulation consisting of longitudinal (I), oblique (II) or transverse (III–V) meshes. Punctation double; 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; fine punctures distributed sparsely and irregularly on ventrite surface. Apical abdominal ventrite (VI) with posterior margin regularly rounded, distinctly beaded; reticulation present only baso-laterally; surface posterolaterally with long and deep longitudinal grooves; punctation sparse but coarser than on other ventrites.

Male genitalia. Median lobe ( Fig. 8a ) in lateral aspect simple, sickle-shaped, slender in median part and distinctly broadened in apical third; apex broadly rounded, distinctly setose on ventral side. Parameres ( Fig. 8b ) narrowly triangular, slender, incised basally; dorsal surface densely setated; apical lobe long.

Female. Identical to male in habitus. Reticulation of dorsal surface more impressed; pro- and mesotarsomeres 1–3 not dilated and without adhesive setae; abdominal ventrite VI with sublateral grooves less developed.

Measurements. TL: 5.4–6.0 mm (mean value: 5.75 ± 0.15 mm); holotype: 5.7 mm. TL-h: 4.8–5.4 mm (mean value: 5.15 ± 0.10 mm); holotype: 5.1 mm. MW: 3.0– 3.5 mm (mean value: 3.25 ± 0.10 mm); holotype: 3.2 mm.

Variability. All specimens of the type series are rather uniform in habitus, reticulation and colouration; minor variability can be seen only in shape and size of yellow elytral markings.

Differential diagnosis. The new species can be recognized from all other Platynectes from the Solomon Islands by combination of extensive yellow dorsal surface pattern ( Fig. 1 ) and the shape of male genitalia ( Fig. 8 ).

Etymology. The new species is named after its area of occurrence – Barana village, in the vicinity of which the new species was collected. The specific epithet is a noun in the nominative singular, standing in apposition.

Collecting circumstances. At the type locality, the species was collected in shaded pools of temporary forest stream ( Fig. 22 ). At the other places, the specimens were collected in pools with muddy bottom made by forest stream. At all places, P. barana sp. nov. was syntopic with P. lunga sp. nov.; at the type locality, both Platynectes were collected together with Carabdytes guadalcanalensis ( Balke, 1998) , Copelatus baranensis Hájek et al., 2021 , C. variistriatus Hájek et al., 2021 , Hyphydrus eldenbecki Biström, 1982 , and Sandracottus femoralis Heller, 1934 .

Distribution. The new species is known from low and medium altitude area (ca. 190–650 m) in north-central Guadalcanal ( Fig. 25A ).

Figures

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.

Figs 8–11. Male genitalia of Platynectes. 8 – P. barana sp. nov.; 9 – P. lunga sp. nov.; 10 – P. makira sp. nov.; 11 – P. malaita sp. nov. a – median lobe in lateral view; b – parameres. Scale bar = 0.5 mm.

Figs 22–24. Habitat of Platynectes in Guadalcanal. 22–23 – type locality of P. barana sp. nov. and P. lunga sp. nov.: 22 – large pool on drying-up stream in forested gorge; 23 – small spring with wet cliff where Platynectes were observed to crawl at night. 24 – forest spring near “Japanese Camp”.

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