Exocelina mekilensis Shaverdo & Balke

Shaverdo, Helena, Surbakti, Suriani, Warikar, Evie L., Sagata, Katayo & Balke, Michael, 2019, Nine new species groups, 15 new species, and one new subspecies of New Guinea diving beetles of the genus Exocelina Broun, 1886 (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 878, pp. 73-143 : 73

3. Exocelina mekilensis Shaverdo & Balke sp. nov. Figs 3 , 9

Exocelina undescribed sp. MB0686: Toussaint et al. 2014: supplementary figs 1-4, tab. 2; Toussaint et al. 2015: supplementary figs S1, S2, tab. S3, and information S5, S6.

Type locality.

Papua New Guinea: Sandaun Province, Ofektaman, 05°04.11'S, 141°35.84'E, 820 m a.s.l.

Type material.

Holotype: male "Papua New Guinea: Sandaun, Ofektaman, 820m, 17.x.2008, 5.04.113S 141.35.841E, Ibalim (PNG 190)", "DNA M.Balke 3723" (ZSM). Paratypes: 1 male with the same label as the holotype (NHMW). 1 male "Papua New Guinea: Sandaun, Sokamin4, 1200m, 19.x.2003, 4 50.845S 141 37.865E, K. Sagata (WB102)", "DNA M. Balke 665" [green text] (ZSM). 1 male, 4 females "Papua New Guinea: Sandaun, MekilW100, 1718m, 14.x.2003, 4 48.637S 141 38.994E, K. Sagata (WB19)" (NHMW, ZSM). 1 male "DNA M. Balke 686" [green text], "Papua New Guinea: Sandaun, Mekil (WB19), 13.x.2003, K. Sagata, DNA M Balke: MB 686" (ZSM).

Description.

Body size and form: Beetle medium-sized: TL-H 3.85-4.4 mm, TL 3.45-3.95 mm, MW 1.8-2.05 mm (holotype: TL-H 3.8 mm, TL 4.2 mm, MW 2.0 mm), with oblong-oval habitus.

Colouration: Dark brown, with paler sides of pronotum and head anteriorly. Head dark brown, piceous posteriorly; pronotum dark brown, with brown sides; elytra uniformly dark brown; head appendages and legs proximally reddish, legs distally darker, reddish brown ( Fig. 3 ). Teneral specimen paler, brown to reddish brown with yellowish pronotal sides.

Surface sculpture: Shiny dorsally, with fine, sparse punctation and weakly impressed microreticulation. Head with relatively fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures almost equal to or smaller than diameter of cells of microreticulation. Pronotum and elytra with much finer and sparser punctation than on head, inconspicuous. Pronotum and elytra with weakly impressed microreticulation. Head with microreticulation slightly stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Venter with extremely inconspicuous punctation, more evident on metacoxal plates and two last abdominal ventrites.

Structures: Pronotum without lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, with distinct bead and few setae laterally. Abdominal ventrite 6 slightly truncate.

Male: Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior band of ca. 60 and posterior row of ten relatively long setae ( Fig. 9D ). Abdominal ventrite 6 with 6-10 lateral striae on each side. Median lobe simple, slightly curved, in lateral view, apex thick, short and slightly curved downwards, its minuscule tip curved upwards ( Fig. 9A, B ). Paramere without notch on dorsal side, evenly tapering to distal part, with numerous small spines and without long setae ( Fig. 9C ).

Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.

Affinities.

From most species co-occurring in the same area ( E. sandaunensis , E. tabubilensis Shaverdo & Balke, 2014, E. damantiensis , E. okbapensis Shaverdo & Balke, 2017, and E. may Shaverdo & Balke, 2017), E. mekilensis sp. nov. can be distinguished by its smaller size and absence of the pronotal bead, and simple male antennae. From the species without pronotal bead ( E. pseudobifidae Shaverdo & Balke, 2014, E. pseudoeme Shaverdo & Balke, 2014, and E. ibalimi Shaverdo & Balke, 2018), it can be differentiated by the shape and setation of its median lobe and paramere, which are very characteristic and resemble those of the E. ullrichi group ( Shaverdo and Balke 2014).

Distribution.

Papua New Guinea: Sandaun Province ( Fig. 11 ).

Etymology.

The species is named after Mekil Village where most specimens of the species were found. The name is an adjective in the nominative singular.

Figures

Figure 9. Exocelina mekilensis sp. nov. A median lobe in ventral view B median lobe in lateral view C paramere in external view D male protarsomeres 4 - 5 in ventral view.

Figure 11. Map of the eastern part of New Guinea showing distribution of the species of the monotypic groups.

Figures 1 - 4. Habitus and colouration 1 Exocelina aipomek (Balke, 1998) 2 E. mekilensis sp. nov. 3 E. koroba sp. nov. 4 E. morobensis sp. nov.