Neosclerus immutatus, Assing, 2011

Assing, Volker, 2011, A revision of the genus Neosclerus C. Supplement I (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 61 (1), pp. 149-153 : 151-153

Neosclerus immutatus sp. n. ( Figs 1-7 )

Type material:

Holotype : "N-Sumatra, 18.2., D. Toba, s-Prapat, Lumban Julu / Indonesia 1990, leg. Schillhammer / Holotypus  Neosclerus immutatus sp. n. det. V. Assing 2010" (cAss) . Paratype : same data as holotype ( NHMW) .

Description:

Body length 3.2-3.5 mm. Habitus as in Fig. 1 . Coloration: head, pronotum, and abdomen blackish; elytra dark-brown with the posterior margin yellow; legs yellowish; antennae reddish-yellow.

Head ( Fig. 2 ) across eyes approximately 1.2 times as wide as long; postocular region very short, almost obsolete; punctation coarse and moderately dense, slightly sparser in posterior portion of dorsal surface; interstices with distinct microreticulation and dull ( Fig. 3 ); antenna 0.9 - 1.0 mm long.

Pronotum ( Fig. 2 ) approximately 1.05 times as wide as long and 0.80-0.85 times as wide as head; impunctate midline defined and rather broad; punctation as coarse and dense as that of head; interstices without microsculpture and glossy.

Elytra ( Fig. 2 ) relatively long and large, approximately 1.1 times as long as pronotum; humeral angles marked; punctation dense and fine; interstices glossy. Hind wings fully developed.

Abdomen narrower than elytra; punctation fine and moderately dense on anterior tergites, somewhat less dense on posterior tergites; interstices with distinct microsculpture composed of isodiametric meshes; posterior margin of tergite VII with palisade fringe.

: sternite VII with posterior margin very weakly concave, pubescence unmodified ( Fig. 4 ); sternite VIII distinctly oblong, anteriorly unmodified and with unmodified pubescence, posterior excision acute, moderately deep, and V-shaped, its depth approximately 1/6 the length of sternite ( Fig. 5 ); aedeagus small, approximately 0.45 mm long, with dorso-ventrally flattened ventral process; internal sac with two long series of small sclerotized structures ( Figs 6-7 ).

Etymology:

The specific epithet (Latin, adjective: unmodified) alludes to the absence of distinct modifications of the male sternite VII and VIII (except for the posterior excision of sternite VIII).

Comparative notes:

Based on the morphology of the aedeagus (ventral process dorso-ventrally flattened; internal sac with two series of small sclerotized spines), N. immutatusimmutatus belongs to the N. fortepunctatus species group. The only other species without distinct modifications of the male sternites VII and VIII, and with a distinctly microsculptured head is N. erubescens ASSING from Malaysia. From this species, N. immutatusimmutatus is readily separated by the much darker coloration of the body, the much less dense punctation of the head and pronotum, the more transverse head, and by the completely different shape of the ventral process of the aedeagus.

In order to account for the new species, the key in ASSING (2011) is modified as follows:

19. : internal sac of aedeagus with two long series of small spines; ventral process of aedeagus slender, apically not spear-shaped. ............................................................................ 19a

- : internal sac of aedeagus with pair of sclerotized structures, but without long series of small spines; ventral process of aedeagus apically spear-shaped, acute and subapically dentate. ................................................................................................................ 22

19a. Head with pronounced microsculpture, dull. : aedeagus shaped as in Figs 6-7 . Sumatra. ........................................................................................ N. immutatus sp. n.

- Head without pronounced microsculpure, glossy. Aedeagus of different shape. .......... 20

Distribution and bionomics:

The type locality is situated at the eastern shore of lake Toba a few kilometres to the south of Prapat in the north of Sumatra. The specimens were collected in February, either from under bark of a dead tree or from between stones and gravel in a dry river bed (SCHILLHAMMER,, pers. comm.).

Figures

Figs 1-7: Neosclerus immutatus sp. n.: habitus (1); forebody (2); head (3); male sternite VII (4); male sternite VIII (5); aedeagus in lateral and in ventral view (6-7). Scale bars: 1: 1.0 mm; 2: 0.5 mm; 4-5: 0.2 mm; 3, 6-7: 0.1 mm.