Exocelina pusilla Shaverdo & Balke

Shaverdo, Helena, Sagata, Katayo & Balke, Michael, 2018, Introduction of the Exocelinacasuarina-group, with a key to its representatives and descriptions of 19 new species from New Guinea (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 803, pp. 7-70 : 35

19. Exocelina pusilla Shaverdo & Balke sp. n. Figs 10, 35

Exocelina undescribed sp. MB1364: Toussaint et al. 2014: supplementary figs 1-4, table 2; Toussaint et al. 2015: supplementary figs S1-S2, table S3.

Exocelina pusilla _New_Guinea_MB1364: Toussaint et al. 2015: supplementary information S5-S6.

Type locality.

Papua New Guinea: Madang Province, Akameku-Brahmin, Bismarck Range, 05°47.03'S, 145°24.13'E, 250-500 m a.s.l.

Type material.

Holotype: male "Papua New Guinea: Madang, Akameku-Brahmin, Bismarck Range, 250-500m, 25.xi.2006, nr 05.47.026S 145.24.131E, Balke & Kinibel (PNG 115)", "M.Balke 1364" [green] (ZSM). Paratypes: Madang: 3 males, 31 exs. with the same label as the holotype (NHMW, ZSM). Simbu: 1 male "Ibisca Niugini, PNG 9-11.xi.2012 Mount Wilhelm 200m", " -5,739897251 145,3297424 FIT-MW200-P-8/8-d16 / Plot 16 / P0835 Vial 14281-CODYTI" (ZSM). 2 females "Ibisca Niugini, PNG 11.ii-11.iv.2012 Mount Wilhelm 200m -5,739897251 145,3297424 MW0200 / P0760 Vial 07137" (ZSM). 1 female "Ibisca Niugini, PNG 2-4.xi.2012 Mount Wilhelm 200m -5,739897251 145,3297424 MW0200 / P0768 Vial 06033" (ZSM).

Description.

Body size and form: Beetle small: TL-H 2.95-3.25 mm, TL 3.2-3.6 mm, MW 1.65-1.85 mm (holotype: TL-H 2.95 mm, TL 3.25 mm, MW 1.65 mm), with oblong-oval habitus.

Coloration: Reddish to reddish brown, with head and pronotum paler. Head yellowish red to reddish, with small darker areas posterior to eyes. Pronotum yellowish red to reddish, with small brownish area on disc. Elytra reddish brown to brown, with narrow reddish sutural lines. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 10). Teneral specimens paler.

Surface sculpture: Shiny dorsally. Head with dense, coarse punctation (no spaces between punctures or spaces 2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures equal to or larger than diameter of cells of microreticulation. Pronotum and elytra with dense and coarse punctation, sparser and finer than on head. Pronotum and elytra with weakly 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 fine sparse punctation.

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

Male: Antennae simple (Fig. 10). Protarsomere 4 with anterior angle slightly expanded and large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 long and narrow, with anterior band of ca 40 and posterior row of 12 relatively long, thin setae (Fig. 35D). Median lobe in lateral view simple, slightly curved; in ventral view, evenly tapering to broadly pointed apex, side of apex slightly thickened. Paramere slightly concave on dorsal side and with dense setae on subdistal part; proximal setae finer and much sparser (Fig. 35 A–C). Abdominal ventrite 6 with 5-10 lateral striae on each side.

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

Affinities.

Exocelina pusilla sp. n. is very similar to E. cyclops sp. n. in body shape, coloration, and surface sculpture but differs in having distinctly thinner and distally narrowed median lobe. It is also similar to E. adelbertensis sp. n., E. bewani sp. n., and E. sumokedi sp. n. but has coarser dorsal punctation and differently shaped median lobe. See also under E. pseudopusilla sp. n.

Distribution.

Papua New Guinea: Madang and Simbu Provinces (Fig. 50).

Etymology.

The species name derives from the Latin “pusillus” (small, tiny) to express small size of these beetles. The species name is an adjective in the nominative singular.