Trisunius cultellatus, Assing, 2011

Assing, V., 2011, Trisunius gen. nov. from the southern East Palaearctic and the Oriental regions (Coleoptera: Staphylinidae: Paederinae: Medonina), Linzer biologische Beiträge 43 (1), pp. 195-220 : 202-205

Trisunius cultellatus nov.sp. ( Figs 17-26 )

T y p e m a t e r i a l: Holotype Ƌ: " China: Yunnan, Lincang Pref., Bangma Shan , 33 km SSW Lincang, 2150 m, 23°35'41''N, 100°00'27''E, decid. forest remnant, N-slope, litter and dead wood sifted, 11.IX.2009, leg. M. Schülke [CH09-42] / Holotypus Ƌ Trisunius cultellatus sp. n. det. V. Assing 2011" (cAss) . Paratypes: 10 exs. [4 teneral]: same data as holotype ( OÖLL, cSch, cAss) ; 4♀♀ [1 teneral]: " China: Yunnan, Pu'er Pref., Ailao Shan, 37 km NW Jingdong, 24°45'12''N, 100°41'24.5''E, 2300 m, devastated forest remnant, litter & dead wood sifted, 13.IX.2009, leg. M. Schülke [CH09-48]" (cSch); 6 exs. [1 teneral]: " China (Yunnan) Baoshan Pref., Gaoligong Shan, 65 km NNE Tengchong 1750 m (sec. mixed forest, overgrown stone debris, litter and moss sifted) 25°35'20''N, 98°40'21''E, 27.VIII.2009 D.W. Wrase [10]" (cSch, cAss); 4 exs. [1 teneral]: " China: Yunnan, Baoshan Pref., Gaoligong Shan , 65 km NNE Tengchong 1750 m, 25°35'20''N, 98°40'21''E, sec. mixed forest, overgrown stone debris, litter and moss sifted, 31.VIII.2009, leg. M. Schülke [CH09-10b]" (cSch, cAss); 6 exs. [5 macropterous]: " China (Yunnan) Baoshan Pref., Gaoligong Shan nr. Xiaoheishan N. R., 35 km SE Tengchong, 2110 m, 24°50'16''N, 98°45'43''E (prim. decid. forest, litter, sifted) 30. V.& 4.VI.2007 D.W. Wrase [11]" (cSch, cAss); 2 exs. [1 macropterous]: " China: Yunnan [CH07-11], Baoshan Pref., Gaoligong Shan, nr. Xiaoheishan N. R., 35 km SE Tengchong, 2110 m, 24°50'16''N, 98°45'43''E, decid. forest, litter, sifted, 30.V.2007, leg. A. Pütz " (cPüt, cAss); 2 exs.: " China: Yunnan [CH07-11A], Baoshan Pref., Gaoligong Shan, nr. Xiaoheishan N. R., 35 km SE Tengchong, 2110 m, 24°50'16''N, 98°45'43''E, decid. forest, fungi, sifted, 4.VI.2007, leg. A. Pütz " (cPüt, cAss); 2 exs.: " China: Yunnan, Dali Bai Aut. Pref., Mao Jiao Shan, E pass, 58 km NE Dali, 25°56'41''N, 100°40'05''E, 2525 m, second. mixed forest, litter, moss & mushrooms sifted, 4.IX.2009, leg. M. Schülke [CH09-26]" (cSch); 1Ƌ: " China (Yunnan) Nujiang Lisu Aut. Pref., creek valley 3 km SE Gongshan, 27°43'02''N, 98°41'27''E, 1450-1500 m (litter, moss, sifted) 5.VI.2007 D.W. Wrase [20]" (cAss) .

D e s c r i p t i o n: Body length 2.7-3.6 mm. Habitus as in Fig. 17 . Coloration of micropterous morph: head usually dark-reddish to reddish-brown, rarely blackish-brown; pronotum reddish to dark-brown; elytra reddish to dark-reddish; abdomen dark-brown to blackish-brown, in pale-coloured specimens distinctly contrasting with the forebody; legs and antennae reddish. Coloration of macropterous morph darker; head and pronotum dark-brown to blackish; elytra variable, dark reddish to predominantly blackish-brown with the posterior margin and the suture indistinctly reddish.

Head as wide as long or indistinctly oblong, weakly dilated behind eyes (micropterous morph) ( Fig. 18 ), or approximately 1.05 times as long as wide, posteriorly subparallel or even narrowed (macropterous morph) ( Fig. 19 ); punctation fine, dense, and shallow; interstices with pronounced microreticulation, almost matt ( Fig. 20 ). Eyes small, approximately one third as long as postocular region in dorsal view (micropterous morph), or larger and somewhat more than half as long as postocular region in dorsal view. Anterior margin of labrum with two distinct teeth on either side of median incision.

Pronotum ( Figs 18-19 ) 1.05-1.1 times as long as wide and approximately 0.9 times as wide as head; punctation rather fine, dense, more distinct than that of head; midline with narrow, complete or anteriorly reduced impunctate band; interstices with shallow microsculpture at least in anterior portion of pronotum (occasionally only faint traces visible), sometimes whole dorsal surface with microsculpture ( Fig. 21 ).

Elytra dimorphic; in micropterous morph short, approximately 0.8 times as long as pronotum and with moderately marked humeral angles ( Fig. 18 ); in macropterous morph approximately 1.1 times as long as pronotum and with pronounced humeral angles ( Fig. 19 ); punctation dense and fine; interstices without microsculpture. Hind wings of reduced length, rudiments slightly projecting from under the elytra when unfolded (micropterous morph), or fully developed. Metatarsomere I approximately as long as II.

Abdomen broader than elytra, widest at segment VI; punctation fine and dense; interstices with distinct microsculpture; posterior margin of tergite VII with palisade fringe.

Ƌ: sternite VII not distinctly modified ( Fig. 23 ); sternite VIII with small posterior excision ( Fig. 24 ); sternite IX as in Fig. 22 ); aedeagus approximately 0.45 mm long, with laterally compressed ventral process of distinctive shape ( Figs 25-26 ).

I n t r a s p e c i f i c v a r i a t i o n: This species is subject to a remarkable dimorphism, this dimorphism not only affecting the length of the elytra and the hind wings, but also the shape of the head and the size of the eyes. A similar phenomenon has been observed also for another paederine, Micrillus torretassoi (KOCH 1934), as well as for several other Staphylinidae such as Vulda ottomana (CAMERON 1912), and Carcinocephalus merkli (EPPELSHEIM 1883) ( ASSING 2007, 2008, 2009a). The aedeagus of both morphs of T. cultellatus is identical. In all, six macropterous specimens (16 %) were examined, all of them from the same locality, where only few micropterous beetles were collected.

E t y m o l o g y: The specific epithet is an adjective derived from the Latin noun cultellus (knife) and refers to the shape of the laterally compressed ventral process of the aedeagus.

C o m p a r a t i v e n o t e s: This species is characterized particularly by the short elytra, the coloration, the pronounced microsculpture of the head, the presence of microsculpture on the pronotum (at least in anterior portion), and by the distinctive shape of the aedeagus.

D i s t r i b u t i o n a n d n a t u r a l h i s t o r y: The type specimens were collected in several localities in Yunnan (Bangma Shan, the Gaoligong Shan, the Ailao Shan, and the Mao Jiao Shan) by sifting forest litter at altitudes of 1450-2525 m in May- June and August-September. Teneral specimens were observed in August and September. Syntopic species are T. spathulatus , T. ligulatus , T. schuelkei , T. iaculatus , and T. truncatus .

Figures

Figs 17-26: Trisunius cultellatus nov.sp.: (17) habitus (micropterous morph); (18) forebody (micropterous morph); (19) forebody (macropterous morph); (20) median dorsal portion of head; (21) median dorsal portion of pronotum; (22) male sternite IX; (23) male sternite VII; (24) male sternite VIII; (25) aedeagus in lateral view; (26) ventral process of aedeagus in ventral view. Scale bars: 17: 1.0 mm; 18-19: 0.5 mm; 23-24: 0.2 mm; 20-22, 25-26: 0.1 mm.