Exocelina oksibilensis Shaverdo, Surbakti, Warikar & 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

9. Exocelina oksibilensis Shaverdo, Surbakti, Warikar & Balke sp. nov. Figs 15 , 21

Type locality.

Indonesia: Papua Province, Pegunungan Bintang Regency, south from Ok Sibil, tributary Digul River 05°03'25.9"S, 140°43'21.1"E, 359 m a.s.l.

Type material.

Holotype: male "Indonesia: Papua, S Ok Sibil, tributary Digul Riv, 359m, 9.vi.2018, -5,05718389 140,722535848617, Sumoked (Pap051)" (MZB). Paratypes: 4 males, 13 females with the same label as the holotype, 2 males with additional labels “6996” [green text], “7001” [green text] (KSP, MZB, ZSM).

Description.

Body size and form: Beetle small: TL-H 3.05-3.35 mm, TL 3.5-3.7 mm, MW 1.7-1.85 mm (holotype: TL-H 3.35 mm, TL 3.7 mm, MW 1.85 mm), usually with oval, egg-shaped habitus.

Colouration: Reddish brown to brown. Head reddish brown to dark brown, paler anteriorly. Pronotum dark brown on disc and narrower or broader reddish on sides. Elytra reddish brown to dark brown, with reddish sutural lines. Head appendages and legs proximally yellowish, legs distally darker, reddish brown ( Fig. 15 ).

Surface sculpture: Shiny dorsally, with fine punctation and weakly impressed microreticulation. Head with fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures equal to or smaller than diameter of cells of microreticulation. Pronotum and elytra with much finer and sparser punctation than on head, sometimes 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. Punctation on venter invisible; inconspicuous on two last abdominal ventrites.

Structures: Pronotum with narrow lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct bead and few setae laterally. Abdominal ventrite 6 slightly truncate.

Male: Protarsomere 4 with anterolateral seta rather long and thing, evenly curved, smaller than more laterally situated large seta. Protarsomere 5 ventrally with anterior band of more than 60 and posterior row of 4 relatively long setae ( Fig. 21D ). Abdominal ventrite 6 with 3-6 lateral striae on each side. Median lobe simple, evenly tapering to broadly pointed apex in lateral and ventral views ( Fig. 21A, B ). Paramere as in Fig. 21C .

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

Affinities.

The species is very similar to E. bacchusi in shape of the median lobe but can be distinguished from it by smaller size and egg-shaped habitus and shorter setae of male protarsomere 4. From the other species co-occurring in the same province ( E. ascendens , E. aipomek , E. takime , the E. ekari group: E. eme Shaverdo and E. bifida , the E. danae group: E. damantiensis and E. danae , the E. okbapensis group: E. ketembang , E. talaki and E. okbapensis , and all species of the E. aipo group), it can be separated by body size and form, presence of pronotal bead, and the shape and setation of its median lobe, paramere, and male protarsomere 4. For the affinities within the group, see the “Key”.

Distribution.

Indonesia: Papua Province, Pegunungan Bintang Regency, Ok Sibil area ( Fig. 25 ).

Etymology.

The species is named after Ok Sibil River. The name is an adjective in the nominative singular.

Figures

Figure 25. Map of the eastern part of New Guinea showing distribution of the species of the E. bacchusi group.

Figures 12 - 17. Habitus and colouration 12 Exocelina oiwa sp. nov. 13 E. akameku sp. nov. 14 E. erteldi (Balke, 1998) 15 E. oksibilensis sp. nov. 16 E. bacchusi (Balke, 1998) 17 E. bacchusi herzogensis sp. nov.

Figures 20, 21. 20 Exocelina erteldi (Balke, 1998) 21 E. oksibilensis 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.