Key to species groups

1 Very small species of 2.0 – 2.3 mm length, abdominal segement VII with long spines. ............ O. coronatus group

- Species usually longer than 2.3 mm, abdominal segment VII without spines. ........................................................... 2

2 Clypeal angles produced to long teeth-like spines or anterior edge of clypeus denticulate and protibia without apical digits; spines directely inserted on outer edge, pronotum with impunctate midline, shorter than 6.0 mm. .......... 3

- Clypeal angles not produced to long spines; if anterior edge of clypeus denticulate or with teeth-like spines, then pronotum without impunctate midline or protibia with long apical digits; if clypeus with central emargination, then species at least 6.9 mm long. ..................................................................................................................................... 4

3 Aedeagus asymmetric, right face of apical lobe sclerotised, left face soft, clypeal angles produced to long spines, spines of protibia not inserted on digits or digits extremely short (WLR: 2.4 – 5.7). .................... O. bicornis group

- Aedeagus symmetric, both sides sclerotised, anterior edge of clypeus denticulate or produced angles of clypeus bidentate, apical protibial digits short (WLR: 1.0 – 3.8). .................................................................. O. oculatus group

4 Head, pronotum and elytra without setiferous punctation or setae extremely short; punctures fine or coarse; apical spines of protibia inserted on long digits. ........................................................................................................................ 5

- Head, pronotum and elytra with setiferous punctation. ................................................................................................ 7

5 Eyes not prominent. ............................................................................................................................................................ 6

- Eyes prominent, punctation of pronotum coarse and dense; pronotum without microsculpture or with weak microsculpture and micro-punctation; apical spines on long digits (WLR: 0.36 – 0.61); last abdominal tergites often with elongate punctation. .................................................................................................. O. guiananus group

6 Punctation of pronotum extremely fine and sparse, microsculpture of pronotum dense and surface matt, apical digits on protibia moderately long (WLR: 0.8). ........................................................................... O. laeviusculus group

- Punctation of pronotum coarse; without microsculpture apical digits on protibia moderately long. ........................ ......................................................................................................................................................................... O. mrazi n. sp.

7 Pronotum and elytra densely pubescent, anterior edge of clypeus even or emarginate, antennomeres more or less equal in width, apical spines of slender protibia inserted on moderatly long digits (WLR: 0.4 – 1.6), between 4.8 mm and 7.8 mm long. ............................................................................................................... O. hirtulus group

- Pronotum and elytra either with dense setiferous punctation and smaller or setiferous punctation distinctly sparser, interstices between punctures at least as wide as diameter of punctures. ................................................................... 8

8 Spines of protibia not inserted on digits or digits wider than long; WLR: higher than 1.0. ..................................... 9

- Outer edge of protibia with distinct apical digits; WLR maximum 1.0. ........................ Group of remaining species

9 Only left face of apical aedeagal lobe sclerotised, mostly small species between 2.5 and 6.5 mm length, only few species longer. .................................................................................................................................. Osoriellus s. str. group

- Aedeagus large and strongly sclerotised, large species, longer than 6.5 mm. .............................. O. granarius group