Exocelina casuarina (Balke & Hendrich, 1998)

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 : 13-15

4. Exocelina casuarina (Balke & Hendrich, 1998) Figs 2, 26

Copelatus (Papuadytes) casuarinus Balke & Hendrich, 1998 in Balke 1998: 328; Nilsson 2001: 76 (catalogue).

Papuadytes casuarinus (Balke & Hendrich, 1998): Nilsson and Fery 2006: 56 (comb. n.).

Exocelina casuarina (Balke & Hendrich, 1998): Nilsson 2007: 33 (comb. n.); Nilsson and Hájek 2018: 65 (catalogue).

Type locality.

Papua: Nabire Regency, 62 km of road Nabire to Enarotali, ca 03°30.936'S, 135°42.945'E, 250 m a.s.l. Note: the road only goes up to Enarotali, Ilaga is much further in the mountains, therefore, people now refer to the road as Nabire-Enarotali.

Type material studied.

Holotype: male "IR 23-W. New Guinea, track Nabire-Ilaga, KM 62, 250m, 24.vii.1991 Balke & Hendrich leg.", “HOLOTYPUS” [red], " Copelatus casuarinus Balke des. 1997" [red] (NHMW). Paratypes: 3 males with the same labels as the holotype and with red labels "Paratypus Copelatus casuarinus Balke des. 1997", one of them additionally with labels "M.Balke 3281" [green] and "M.Balke 6408" [green text] (NHMW).

Additional material.

1 female "IRIAN JAYA: Paniai Prov. road Nabire-Ilaga, km 65 29.8.1996, 250m leg. M. Balke (96 # 6)" (NHMW). 4 males, 2 females "West New Guinea/Paniai Prov/JR 22 track Nabire-Ilaga km 62 250m, 24.7.1991, forest pools leg. Balke & Hendrich" (CLH). 1 male "W.-Neuguinea/Paniai Prov. Straße Nabire-Ilaga km 5 700m, 22.-2.9.1990/IR 11 leg: Balke & Hendrich" (CLH).

Diagnosis.

For complete description, see Balke (1998: 328). Beetle medium-sized: TL-H 3.6-4.05 mm; oblong-oval; reddish brown to dark brown, sometimes with reddish to reddish brown pronotal sides and head anteriorly; submatt, with fine but rather dense punctation and strongly impressed microreticulation; pronotum without lateral bead; male antennae simple (Fig. 2); male protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta; male protarsomere 5 long and narrow, with anterior band of more than 60 and posterior row of 12 relatively long, thin setae (Fig. 26D); median lobe in lateral view slightly curved and apically rounded, in ventral view, almost subparallel and not narrowed before truncate or slightly concave apex; paramere slightly concave on dorsal side and with long, dense, thin setae, situated along dorsal margin: subdistal setae strong and dense, setae in middle part shorter and sparser, proximal setae long but sparser than subdistal ones (Fig. 26 A–C). Female without evident differences in external morphology from males, except for non-modified pro- and mesotarsi and abdominal ventrite 6 without striae.

Affinities.

Exocelina casuarina is the only species of the casuarina -group in Nabire Regency. In this area, Exocelina is represented mainly by the species of the ekari -group, which are small in size and have no pronotal bead. From them, as well as from E. ransikiensis Shaverdo et al., 2016d with the same characters, the species differs in larger size and the different shape of the median lobe. From E. bagus ((Balke & Hendrich, 2001), in Balke (2001)), which is similar in size and surface sculpture to E. casuarina , the species differs in simple male antennae and the different shape of the median lobe. From E. damantiensis (Balke, 1998) of the danae -group, the only species with the pronotal bead in the Nabire-Enarotali area, E. casuarina differs in absence of the pronotal bead, evidently stronger dorsal punctation and microreticulation, and the different shape of the median lobe.

Within the casuarina -group, the species is more similar to E. fume (Balke, 1998) and E. ibalimi sp. n., with which it shares not only absence of the pronotal bead, but also a large, strongly curved anterolateral hook-like seta of the male protarsomere 4 (see their “Affinities” and the “Key”).

Distribution.

Papua: Nabire Regency. The species is known only from the area close to the type locality (Fig. 50).