Platynectes owaraha, 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 : 67-68

Platynectes owaraha sp. nov.

( Figs 6 , 14 )

Platynectes insularis J. Balfour-Browne, 1939: 466 (partim). Platynectes semperi Régimbart, 1899 : GUḖORGUIEV (1972): 53 (partim).

Type locality. Solomon Islands, Owaraha.

Type material. HOLOTYPE: J ( BMNH), labelled: ‘Para- / type [p, round label with yellow frame] // British Solomons [p] / … [illegible] 193 [p] 2 [hw] / R.J.A.W.Lewer [p] / [on reverse:] Santa Ana [hw] // Pres.by / Imp.Inst.Ent. / B.M.1936-90. [p] // Platynectes / insularis m. [hw] / J.Balfour-Browne det. [p] // HOLOTYPE J / PLATYNECTES / owaraha sp. nov. / J. Hájek et al. det. 2021 [p, red label]’. PARATYPE: 1 ♀, labelled: ‘Para- / type [p, round label with yellow frame] // with stream [hw] British Solomons [p] / … [illegible] 193 [p] 2 [hw] / R.J.A.W.Lewer [p] / [on reverse:] Santa / Ana [hw] // Pres.by / Imp.Inst.Ent. / B.M.1936-90. [p] // Platynectes / insularis m. [hw] / J.Balfour-Browne det. [p]’ ( BMNH). The paratype with the respective red printed label.

Additional material studied. 1 J (immature specimen without left elytron): San Cristoval [Makira], Pagato R. [River], camp 2 [ca. 10°34.9′S, 162°02.7′E], rocks in midstream, 3.viii.[19]65, Roy. Soc. Exped. ( BMNH).

Description. Male holotype. Habitus. Broadest in one third of elytral length; body outline continuous.

Colouration ( Fig. 6 ). Head along anterior margin anteriorly from eyes orange-brown, with round orange spot between eyes and two transverse spots on vertex; appendages orange-brown. Pronotum with broadly orange-brown sides and anterior corners; basal margin and disc of pronotum somewhat brownish translucent. Scutellum black, brownish translucent. Elytron black with brownish lateral margin and epipleura, disc with distinct yellow-orange pattern consisting of, one postmedial spot in two thirds of elytral length, one subapical spot and band along lateral margin; postmedial spot transverse, somewhat divided longitudinally to two parts, connected with longitudinal lateral band; preapical spot large, connected with longitudinal lateral band; lateral longitudinal band broad and distinct, starting at about elytral midlength and ending close to apex. Legs orange-brown. Ventral surface with brown head, prosternum, mesoventrite and lateral parts of metaventrite; medial part of metaventrite, metacoxal plates and abdominal ventrites darker, brown-blackish; apical ventrite orange-brown medio-posteriorly.

Head ca. 0.65× width of pronotum, transversely elliptical. Meshes of reticulation mostly complete (not closed); reticulation absent anteriorly on clypeus. Microreticulation absent.

Pronotum. Reticulation similar to that of head, consisting of heterogeneous polygonal meshes; meshes smaller, incomplete and less impressed on disc, becoming larger, closed and deeply impressed near sides. Microreticulation absent. Centre of pronotal disc with small longitudinal furrow.

Elytra. Punctation double; coarse punctures present in two discal and two lateral longitudinal lines; fine punctures 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 third of elytra.

Ventral surface. Medial part of metaventrite without microsculpture, shiny, with sparse fine punctation. Ratio WC/WS = 4.50. Metacoxal lines incomplete anteriorly, slightly divergent. Metacoxal plates reticulated with polygonal meshes; surface with short longitudinal strioles; 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. 14a ) in lateral aspect slender in median part, only slightly widened to apex; apex broadly rounded, distinctly setose on ventral side. Parameres ( Fig. 14b ) narrowly triangular, slender, incised basally; dorsal surface densely setated; apical lobe long.

Female. Identical to male in habitus. Elytral reticulation slightly more impressed, traces of microreticulation better perceptible.

Measurements. TL: 5.6–5.9 mm; holotype: 5.6 mm. TL-h: 5.0– 5.4 mm; holotype: 5.05 mm. MW: 3.0– 3.1 mm; holotype: 3.0 mm.

Variability. No substantial variability can be seen in the limited material available for the study.

Differential diagnosis. Smallest (5.6–5.9 mm) of all Platynectes from Solomon Islands. Platynectes owaraha sp. nov. differs from similar and sympatric P. makira sp. nov. in more parallel-sided habitus; reticulation of pronotum well developed also on centre of disc; in different elytral colouration comprising only one postmedian and one subapical spot, and broad lateral longitudinal band which is beginning at about elytral midlength (cf. Figs 3 and 6 ); and in male median lobe, which is slightly widened to broadly rounded apex in lateral view ( Fig. 14 ).

Two specimens of P. owaraha sp. nov. from Santa Ana (Owaraha) were part of the type series of P. insularis occurring in Vanuatu. Indeed, with small body length, and with elytral pattern, P. owaraha sp. nov. resembles the latter species. However, P. owaraha sp. nov. differs from P. insularis in more parallel-sided, dorsally more convex habitus; much broader beading of lateral sides of pronotum; elytral reticulation less impressed with meshes much more frequently incomplete (not closed); longitudinal lines of serial punctures on elytra more distinct; and prosternal column broadly convex.

Etymology. The new species is named after its area of occurrence – Owaraha Island, also known as Santa Ana. The specific epithet is a noun in the nominative singular, standing in apposition.

Collecting circumstances. Based on the label data, the specimens were collected in streams. Probably a lowland species; the highest point of Owaraha reaches altitude 150 m a.s.l., the single specimen from Makira was collected at altitude about 40 m a.s.l.

Distribution. The new species is known from small island Owaraha and nearby Makira Island ( Fig. 25A ).

Figures

Figs 4–6. Habitus of Platynectes in dorsal (a) and frontolateral (b) view. 4 – P.malaita sp. nov.; 5 – P.mbaole sp. nov.; 6 – P.owaraha sp. nov. Not to scale.

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.

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.

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