Exocelina amabilis Shaverdo & Balke, 2020

Shaverdo, Helena, Surbakti, Suriani, Sumoked, Bob & Balke, Michael, 2020, Three new species of Exocelina Broun, 1886 from the southern slopes of the New Guinea central range, with introduction of the Exocelina skalei group (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 1007, pp. 129-143 : 129

Exocelina amabilis Shaverdo & Balke sp. nov. Figs 5 , 6 , 7

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 [River], 359m, 9.vi.2015, -5,05718389 140,722535848617, Sumoked (Pap051)" (MZB). Paratypes: 3 males, 8 females with the same label as the holotype, 2 males additionally with green text label “6997” and “6998” (KSP, MZB).

Description.

Body size and form: Beetle small: TL-H 2.65-3.45 mm, TL 3.55-3.85 mm, MW 1.75-1.9 mm (holotype: TL-H 3.25 mm, TL 3.65 mm, MW 1.8 mm), with oblong-oval habitus (Fig. 6 ).

Colouration: Dorsally piceous (Fig. 6 ), with dark brown posterior part of head and lateral parts of pronotum, and sometimes with middle part of pronotum and elytral sutural lines; head appendages and legs yellowish-red, metathoracic legs darker distally.

Surface sculpture: Relatively shiny dorsally, with very fine, sparse punctation and distinctly impressed microreticulation. Head with dense punctation (spaces between punctures 1-3 times size of punctures), distinctly finer and sparser anteriorly and posteriorly; diameter of punctures almost equal to diameter of cells of microreticulation. Pronotum with much sparser and finer punctation than head. Elytra with very sparse and fine punctation, often inconspicuous. Pronotum and elytra with distinctly impressed microreticulation; head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine and sparse punctation.

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 lateral bead and few setae.

Male: Antenna simple. Pro- and mesotarsomeres 1-3 not dilated. Protarsomere 4 cylindrical, narrow, with medium-sized, thick, slightly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior row of 12 and posterior row of 6 short, thick, pointed setae (Fig. 7D ). Median lobe with slightly discontinuous outline (see apically); in lateral view, more or less evenly curved, with broadly pointed apex; in ventral view, tapering to broadly pointed apex (Fig. 7A, B ). Paramere with very deep dorsal notch, separating subdistal part; subdistal part broad, transverse, situated under apex of proximal part, with large tuft of dense, thick, flattened setae; proximal setae sparse, thin, much more inconspicuous than subdistal (Fig. 7C ). Abdominal ventrite 6 with extremely weak, small medial impression, visible only apically, concave apically, with 12-16 lateral striae on each side.

Female: Pro- and mesotarsi not modified. Abdominal ventrite 6 slightly truncate or very slightly concave apically, without medial impression and lateral striae.

Habitat.

The specimens were collected from the gravel banks of a primary forest stream. The beetles were mainly hidden in the coarse gravel and were only obtained after some digging.

Distribution.

Indonesia: Papua Province. The species is known only from the type locality (Fig. 5 ).

Etymology.

The species name is a Latin adjective and means “loveable”.

Affinities.

The species evidently belongs to the E. ekari group due to the discontinuous outline of its median lobe. It is similar to E. utowaensis Shaverdo, Hendrich & Balke, 2012 in modification of the abdominal ventrite 6, body size, colouration and shape but distinctly differs from it in having a pronotal bead (absent in E. utowaensis ) and different shape of the median lobe, paramere, and anterolateral hook-like seta of the male protarsomere 4 (it is also larger in E. utowaensis ). The species is also similar to E. athesphatos in modification of the abdominal ventrite 6 and paramere, but distinctly differs from it in smaller size and having simple male antennae.

Figures

Figure 5. Map of the western part of New Guinea showing the species distribution.

Figure 6. Habitus and colouration of Exocelina amabilis sp. nov., holotype.

Figure 7. Exocelina amabilis sp. nov., paratype A median lobe in ventral view B median lobe in lateral view C right paramere in external view D right male protarsomeres 4 - 5 in ventral view.