Lathrobium volutum, Assing, 2015

Assing, Volker, 2015, New species and additional records of Lathrobium and Elytrobium from the Palaearctic region, with special reference to the fauna of East Yunnan (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 65 (1), pp. 41-74 : 71

Lathrobium volutum spec. nov.

( Figs 126–134 )

Type material: Holotype : “ JAPAN, Honshu, Iwate, Kawai, Yoshibezawa [39°37'N, 141°31'E], 600–700 m, 16. VIII.91, A. Smetana [J57] / Holotypus  Lathrobium volutum spec. nov., det. V. Assing 2014” ( CNC).

Paratypes: 1 , 2 : same data as holotype ( CNC, cAss) .

Etymology: The specific epithet is the past participle of the Latin verb volvere (to roll) and alludes to the shape of the internal structure of the aedeagus.

Description: Body length 6.5–7.5 mm; length of forebody 3.4–3.6 mm. Habitus as in Fig. 126 . Coloration: body blackish-brown to blackish; legs yellowish-brown; antennae dark-reddish.

Head ( Fig. 127 ) weakly transverse, 1.02–1.04 times as broad as long; punctation moderately coarse and moderately dense, sparser in median dorsal portion; interstices with distinct microreticulation. Eyes weakly projecting from lateral contours of head, approximately one-third as long as postocular region in dorsal view, or even shorter, and composed of approximately 50 ommatidia. Antenna approximately 1.8 mm long.

Pronotum ( Fig. 127 ) approximately 1.2 times as long as broad and about as broad as head; punctation similar to that of head, but somewhat sparser; impunctate midline moderately broad; interstices without microsculpture.

Elytra ( Fig. 127 ) approximately 0.55 times as long as pronotum, weakly dilated posteriad; humeral angles weakly marked; punctation shallow and moderately dense; interstices without microsculpture. Hind wings completely reduced. Protarsomeres I–IV with pronounced sexual dimorphism.

Abdomen distinctly broader than elytra; punctation fine and moderately dense, density decreasing towards posterior tergites; posterior margin of tergite VII without palisade fringe; tergite VIII with sexual dimorphism.

: protarsomeres I–IV strongly dilated; posterior margin of tergite VIII truncate; sternite VII ( Fig. 128 ) strongly transverse, with impression of subtriangular shape in postero-median portion, this impression with moderately dense and moderately modified black setae, posterior margin distinctly concave in the middle; sternite VIII ( Fig. 129 ) weakly transverse and longitudinally impressed in postero-median portion, posterior excision small and U-shaped, on either side of posterior excision weakly produced, posterior portion with dense stout black setae; aedeagus ( Figs 130–131 ) 1.7 mm long and symmetric; ventral process long, weakly curved in lateral view, apically acute, with a pronounced median carina ventrally; dorsal plate with a long, distinctly sclerotized, dorsally weakly excavate, and apically dentate apical portion ( Fig. 132 ) and with a shorter lamellate basal portion; internal sac with a broad, curved (cross-section), and moderately sclerotized structure.

: protarsomeres I–IV moderately dilated, distinctly less so than in male; posterior margin of tergite VIII convex; sternite VIII ( Fig. 133 ) longer than tergite VIII, convexly produced posteriorly; tergite IX ( Fig. 134 ) with very long and undivided antero-median portion and short postero-lateral processes; tergite X ( Fig. 134 ) short, little more than one-third as long as antero-median portion of tergite IX.

Comparative notes: Based on the similarly modified male sternites VII and VIII, as well as the similar general morphology of the aedeagus, particularly the presence of an internal structure of similar general shape, L. volutum is very closely allied to the syntopic L. scaphiforme , from which it differs by distinctly smaller size, the more slender habitus, the less pronounced median concavity of the male sternite VII, the different shape and chaetotaxy of the male sternite VIII, the different shapes of the ventral process and the dorsal plate of the aedeagus, the relatively longer antero-median portion of the female tergite IX, and the shorter female tergite X.

Distribution and natural history: The type locality is situated near Kawai (northern Honshu: Iwate Prefecture) at an altitude of 600– 700 m. The specimens were collected together with the holotype of L. scaphiforme .

Figures

Figs 126–142: Lathrobium volutum spec. nov. (126–134) and L. trabale spec. nov. (135–142): habitus (126, 135); forebody (127, 136); male sternite VII (128, 138); male sternite VIII (129, 139); aedeagus in lateral view (130, 140); aedeagus in ventral view (131); apical portion of dorsal plate of aedeagus in lateral view (132); female sternite VIII (133, 141); female tergites IX–X (134, 142); abdominal segments III–VII (137). Scale bars: 126–127, 135–137: 1.0 mm; 128–131, 133–134, 138–142: 0.5 mm; 132: 0.1 mm.