Osorius alternans BERNHAUER

Irmler, Ulrich, 2010, The Neotropical species of the genus Osorius G - M, 1829 with remarks to the Neotropical Osoriid complex (Coleoptera: Staphylinidae: Osoriinae), Beiträge Zur Entomologie = Contributions to Entomology 60 (2), pp. 363-426 : 374-375

Osorius alternans BERNHAUER ,, 1920: 137 (Figs 3a-f)

Type material examined:

Peru: Lima, leg. Linke, 1 male without further data (syntype, FMNH) ; Bolivia: Yuracaris 1 female (syntype, FMNH) .

Additional material examined:

Bolivia: Yuracaris , 1500 m elevation, 1 specimen ( FMNH) ; Peru: San Ramon (75°17' W, 11°02' W), 1 specimen, 9.9.1906, leg. Iconikoff ( FMNH) ; Iquitos, lowland forest, Rio Napo and Rio Sucusari , 1 specimen, Dec. 1998, leg. Bracley ( BMNH) ; Loreto, Boqueron del Padre Abad , 7 specimens, 8.8.1946, leg. F. Woytkowski ( AMNH) ; San Martin, 2 specimens, 9.3.194, leg. F. Woytkowski ( AMNH) ; La Merced, 15 km E, Pasco, 1 specimen, 24.11.1971, leg. R.T.Schuh ( AMNH) ; Bagua (78°30' W, 5°38' S), Montenegro, Amazonas , 1 specimen, 2.10.1963, F. Wygodzinski ( AMNH) ; Tingo Maria (75°59' W, 9°17' S), 1 specimen, 21.10.1947, leg. J. Pallister ( AMNH) ; Madre de Dios, Manu National Park, Cocha Otorongo , under bark (71°11'58 W, 12°02'1 S), 310 m elevation, 5 specimens, 21.10.2000 leg. R.W. Brooks ( KU, UIC) ; Villa Rica (74.50 W, 10.08 S); 15 km E, Pasco, 100 m elevation, 2 specimens, 24.11.1971, leg. R.T. Schuh ( AMNH) ; Tambopata: Puerto Maldonado (69.12 W, 12.37 S), 15 km N, ex molassas, 200 m elevation, 2 specimens, 11.07.1989, leg. J.S. Ashe ( KU) ; Madre de Dios: Pentiacolla Lodge, Monk Saki Trail , under bark, 1 specimen, 25.10.2000, leg. R.W. Brooks ( KU) ; Ecuador: Sucumbios, Sacha Lodge (76°5' W, 0°5' S), 4 specimens, 22.03.1999, leg. R.W. Brooks ( KU, UIC) ; Sacha Lodge , 5 specimens, 28.10.2004, leg. Rougemont ( RC, UIC) ; La Bonita (77°32' W, 0°24'1 N), 17.5 km S, Santa Barbara Rd. , 1 specimen, 11.10.1998, leg. D. Brzoska ( KU) ; Napo, Jatun Sacha , 16 km E Puerto Napo, rain forest, under bark (77°37'42 W, 1°03'57 S), 1 specimen, 22.7.2009, leg. U. Irmler ( UIC) .

Diagnosis:

BERNHAUERBERNHAUER (1920) already mentioned the high similarity between O. alternans and O. stipes . Even the differences noted by Bernhauer could not be considered to be constant in a larger number of specimens. The short labrum mentioned by BERNHAUERBERNHAUER (1920) is no valid character, because the labrum in Osorius can be moved fore and back by the beetle and is thus variably covered by the clypeus. I found no significant constant characters to identify the two species except in the shape of the aedeagus. After studying the type species I was convinced that O. alternansalternans is synonym to O. stipes . However, after the study of a number of specimens from the eastern Andean region, no variation was found in the aedeagus of the specimens of this region. It is clearly different from the Central Amazonian specimens. Thus, O. alternansalternans seems to be a distinct species. The aedeagus in O. alternansalternans has a short, very small, even apex, whereas the aedeagus in O. stipes has a longer acute apex.

Description:

Length: 11.5 – 13.5 mm. Colour: black.

Head :: 1.5 – 2.0 mm long, 2.5 – 3.1 mm wide; eyes not prominent; slightly shorter than temples; with numerous supraocular and postocular striae; irregular punctation moderately deep and dense; on average distance between punctures two times wider than diameter of punctures; an impunctate space at base of antennae and an adjacent space with sparser punctation on each side of disc; close to neck a further transversal space with sparser punctation; on each side of clypeus with denser granular punctation; few granular punctures also between eyes and neck; on each side of disc with two supraocular setiferous punctures and three setiferous punctures in front of eyes; microsculpture densely netlike reticulate; surface only slightly shiny.

AntennaeAntennae one third longer than head; 2 nd antennomere short and globular; 3 rd antennomere nearly two times longer than 2 nd; subsequent antennomeres slightly increasing in width; 4 th to 6 th antennomeres more or less quadrate; subsequent antennomeres slightly wider than long.

Pronotum: 2.1 – 2.5 mm long, 2.6 – 3.3 mm wide; widest at anterior tooth-like prominent angles; narrowed to posterior angles; in front of posterior angles slightly emarginate; a second smooth emargination in anterior half; lateral margin narrow in anterior half, widened in posterior half; punctation deep, but sparser than on head; distance between punctures 2.5 to 3 times wider than diameter of punctures; with small impunctate midline; midline with short furrow in posterior half; netlike microsculpture deeper and more distinct than on head; surface less shiny than on head.

Elytra: 2.6 – 3.3 mm long, 2.7 – 3.4 mm wide; with coriaceous ground sculpture, but without microsculpture; sparse punctation nearly invisible in coarse ground sculpture; surface shinier than on pronotum and head; nearly polished between striae of ground sculpture.

AedeagusAedeagus relatively slender with short apical part; apex obtuse and slightly curved back.