Exocelina atrata (Balfour-Browne, 1939)

Shaverdo, Helena, Sagata, Katayo & Balke, Michael, 2016, Taxonomic revision of New Guinea diving beetles of the Exocelinadanae group, with the description of ten new species (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 619, pp. 45-102 : 52-53

Taxon classification Animalia Coleoptera Dytiscidae

5. Exocelina atrata (Balfour-Browne, 1939) Figs 22, 36

Copelatus atratus J. Balfour-Browne 1939: 66; Guignot 1956: 55 (catalogue); Guéorguiev 1968: 32 (catalogue); Guéorguiev and Rocchi 1993: 161 (catalogue).

Copelatus (Papuadytes) atratus J. Balfour-Browne, 1939: Balke 1998: 326 (notes, diagnosis); Nilsson 2001: 76 (catalogue).

Papuadytes atratus (J. Balfour-Browne, 1939): Nilsson and Fery 2006: 56 (comb. n.).

Exocelina atrata (J. Balfour-Browne, 1939): Nilsson 2007: 33 (comb. n.).

Type locality.

Papua New Guinea: Oro (Northern) Province, Kokoda, approximately 08°53'S; 147°44'E, approximately 366 m a.s.l.

Type material.

Holotype: male “Type” [round, with red bead], "Under stones: river side.", "PAPUA:Kokoda. 1,200ft. viii.1933. L.E.Cheesman. B.M.1933-577.", " Copelatus atratus , ♂ Type nov.sp." [hw, blue ink, the word “type” with red ink], “Holotype” [red] (BMNH). Paratypes: 1 female “Type” [round, with red bead], "Under stones: river side.", "PAPUA:Kokoda. 1,200ft. viii.1933. L.E.Cheesman. B.M.1933-577.", " Copelatus atratus , ♀ Type nov.sp." [hw, blue ink, the word “type” with red ink] (BMNH). 4 males, 1 female “Co-type” [round, with yellow bead], "Under stones: river side.", "PAPUA:Kokoda. 1,200ft. viii.1933. L.E.Cheesman. B.M.1933-577.", " Copelatus atratus , ♂ [or ♀] Cotype nov.sp." [hw, blue ink, the word “Cotype” with red ink] (BMNH). 4 males “Co-type” [round, with yellow bead], "PAPUA:Kokoda. 1,200ft. vi-vii.1933. L.E.Cheesman. B.M.1933-427.", " Copelatus atratus , B-B ♂ Co-type." [hw, black ink] (BMNH).

Diagnosis.

Beetle medium-sized, dark brown, with paler, reddish-brown, head and pronotal sides; dorsal surface with fine punctation and evident microreticulation, shiny; pronotum with distinct lateral bead; male antennomeres simple; male protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta; median lobe broad, with almost parallel sides and broadly rounded apex in ventral view and with slightly curved apex, some short distal setae in lateral view; paramere without notch on dorsal side.

Redescription.

Size and shape: Beetle medium-sized (TL-H 4.20-4.25 mm, TL 4.75 mm, MW 2.25 mm), with rather oblong habitus, broadest at elytral middle. Coloration: Head dark brown, with reddish-brown clypeus and vertex; pronotum dark brown on disc and reddish-brown on sides; elytra uniformly dark brown; ventrally pale brown to brown, slightly darker on metacoxal plates; head appendages yellowish-brown to reddish-brown, legs darker distally (Fig. 36).

Surface sculpture: Head with dense and coarse punctation (spaces between punctures 1-2 times size of punctures); diameter of punctures smaller than diameter of cells of microreticulation. Pronotum with evident, dense punctation, finer, sparser than on head. Elytra with finer, sparser punctation than on pronotum, punctation fine but distinct. Pronotum and elytra with distinct microreticulation, dorsal surface shiny. Head with microreticulation slightly stronger. Metaventrite, metacoxa, and abdominal ventrites distinctly microreticulate, but with cells of microreticulation larger than on dorsal side. Metacoxal plates with longitudinal strioles and transverse wrinkles; abdominal ventrites with strioles. Ventrum with inconspicuous punctation, more evident on metacoxal plates and two last abdominal ventrites.

Structures: Pronotum with distinct lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, smooth anteriorly, without anterolateral extensions. Blade of prosternal process lanceolate, relatively narrow, convex, with distinct bead and few setae laterally; neck and blade of prosternal process evenly jointed. Abdominal ventrite 6 truncate apically.

Male: Antenna simple. Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with dense anterior band of ca. 70 relatively long, thin setae and posterior row of 15 similar setae (Fig. 22A). Abdominal ventrite 6 with 4-5 lateral striae on each side. Median lobe broad, with almost parallel sides and slightly concave apex in ventral view and with slightly curved apex, some short distal setae situated in small groups under very fine carinas in lateral view; ventral sclerite of medial lobe as long as median lobe or slightly longer (Fig. 22 B–C). Paramere without notch, slightly concave on dorsal side, with thin, sparse, inconspicuous proximal setae and thicker, denser, and longer subdistal setae (Fig. 22D).

Female: Without evident differences in external morphology from males, except for not modified pro- and mesotarsi and abdominal ventrite 6 rounded apically, without striae.

Distribution.

Papua New Guinea: Oro (Northern) Province. The species is known only from its type locality (Fig. 40).