Lathrobium (Lathrobium) involutum, Assing, 2010

Assing, Volker, 2010, On the Lathrobiina of Taiwan (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 60 (2), pp. 301-361 : 305-307

Lathrobium (Lathrobium) involutum sp. n. ( Figs 1-9 )

Type material:

Holotype ♂: " Taiwan, Taichung Hsien, Hseuhshan, above Shan-Liu-Gieu Hut , 3220 m, 7. V.91, A. Smetana [ T69 ] / Holotypus ♂ Lathrobium involutum sp. n., det. V. Assing 2010" (cSme) . Paratypes: 15 exs.: same data as holotype (cSme, cAss) ; 7 exs.: " Taiwan, Taichung Hsien, Hseuhshan, above Shan-Liu-Gieu Hut , 3150 m, 8. V.91, A. Smetana [ T71 ]" (cSme, cAss); 13 exs.: " Taiwan, Taichung Hsien, Hseuhshan, above Shan-Liu-Gieu Hut, 3200 m, 8. V.91, A. Smetana [ T72 ]" (cSme, cAss); 27 exs.: " Taiwan, Taichung Hsien, Hseuhshan, Hseuhshan Main Peak, 3650 m, 9. V.91, A. Smetana [ T73 ]" (cSme, cAss); 4 exs.: " Taiwan, Taichung Hsien, Hseuhshan, Hseuhshan Mn. Pk., 3750-3884 m, 9. V.91, A. Smetana [ T74 ]" (cSme, cAss); 1 ex.: " Taiwan, Taichung Hsien , Hseuhshan , above Shan-Liu-Gieu Hut , 3350 m, 10. V.91, A. Smetana [ T75 ]" (cAss) .

Description:

Body length 4.8-6.0 mm; habitus as in Fig. 1 . Coloration: body uniformly pale-reddish.

Head weakly oblong, 1.05-1.10 times as long as wide; punctation moderately coarse and of variable density, sparser in median dorsal area; interstices with very shallow microreticulation; lateral contours behind eyes weakly convex in dorsal view; eyes small, not protruding from lateral contours of head and approximately 1/5-1/4 the length of postocular region in dorsal view. Antenna rather stout; antennomeres II and III of subequal length and approximately 1.5 times as long as wide; IV-VII approximately as long as wide; VIII-X weakly transverse.

Pronotum slender, approximately 1.3 times as long as wide and about as wide as head ( Fig. 2 ); lateral margins often weakly sinuate slightly before middle; punctation similar to that of head, but often slightly less coarse; interstices without microsculpture.

Elytra short, 0.55-0.60 times as long as pronotum ( Fig. 2 ); punctation fine, shallow, weakly defined; interstices without apparent microsculpture, but sometimes somewhat rugosely sculptured. Hind wings completely reduced.

Abdomen 1.10-1.25 times as wide as elytra; punctation fine and very dense; interstices with distinct microsculpture and rather matt; posterior margin of tergite VII without palisade fringe.

♂: sternite VII with posterior margin weakly concave in the middle, pubescence weakly modified ( Fig. 3 ); tergite VIII with weakly convex posterior margin; sternite VIII almost 1.1 times as long as wide, excision almost V-shaped, its depth approximately 1/10 the length of sternite ( Fig. 4 ); aedeagus approximately 0.95 mm long, with ventral process, internal structures, and dorsal plate of distinctive morphology ( Figs 5-6 ).

♀: tergite VIII with broadly and weakly concave posterior margin ( Fig. 7 ), latero-ventrally extended into pronounced flaps, which meet and even overlap ventrally and envelop all of the abdomen; sternite VIII distinctly oblong, approximately 1.3 times as long as broad, much longer than tergite VIII, and distinctly produced posteriorly ( Fig. 8 ); tergite IX narrowly membranous in the middle ( Fig. 9 ); tergite X approximately twice as long as tergite IX in the middle.

Comparative notes:

This new species is readily distinguished from the four previously described congeners from Taiwan particularly by the different morphology of the aedeagus. In addition, it is separated from them as follows:

from L. taiwanensetaiwanense (Taichung Hsien: Hsiao-hsüeh Shan) by much smaller size ( L. taiwanense 7.9 mm), much coarser and sparser punctation of head and pronotum, the differently shaped head ( L. taiwanense : suborbicular), smaller eyes, more oblong pronotum ( L. taiwanense : 1.19 times as long as broad), stouter antennae, and the different shape and chaetotaxy of the male sternite VII and VIII;

from L. shaolaiense (Taichung Hsien: Shao-lai Shan) by much smaller size ( L. shaolaiense : 7.9 mm), smaller eyes ( L. shaolaiense : approximately 1/3 as long as postocular region in dorsal view), more oblong pronotum ( L. shaolaiense : 1.13 times as long as broad), and the absence of pronounced impressions on the male sternites V-VIII;

from L. yasutoshiiyasutoshii (Taichung Hsien: Lishan) by smaller size ( L. yasutoshii : 6.4-9.1 mm), paler coloration, smaller eyes ( L. yasutoshii : slightly less than 1/3 the length of postocular region in dorsal view), more oblong pronotum ( L. yasutoshii : 1.13 times as long as broad), and the different modifications of the male sternites VII and VIII;

from L. tsuifengensetsuifengense (Nantou Hsien:Tsuifeng) by smaller size ( L. tsuifengense : 6.5-8.1 mm), smaller eyes ( L. tsuifengense : more than 1/3 as long as postocular region in dorsal view), the more oblong pronotum ( L. tsuifengense : 1.18 times as long as broad), and the different shape and chaetotaxy of the male sternites VII and VIII.

For illustrations of the habitus, the male secondary sexual characters, and the aedeagus of the compared species see WATANABE (1998, 2005).

Etymology:

The specific epithet (adjective, past participle of involvere) refers to the remarkable morphology of the female tergite VIII.

Distribution and natural history:

As can be inferred from the adaptive reductions of eye size, pigmentation, wings, and of the palisade fringe at the posterior margin of the abdominal tergite VII, as well as from the evidently restricted distributions of other species of the L. involutum group, the species is probably endemic to the Hseuhshan mountain range, Taichung, central Taiwan. The type specimens were sifted from leaf litter, moss, and other debris in an old coniferous forest and in stands of rhododendron and juniper at altitudes of 3150-3884 m .

Figures

Figs 1-10: Lathrobium involutum sp. n. (1-9) and L. alishanum sp. n. (10): habitus (1); forebody (2); male sternite VII (3); male sternite VIII (4); aedeagus in lateral view (5-6); female tergite VIII (7); female sternite VIII (8); female tergites IX-X (9); head in lateral view (10). Scale bars: 1-2: 1.0 mm; 3-4, 7-10: 0.5 mm; 5-6: 0.2 mm.