(Modified from Fernández and Sarmiento-M., 2002)
1 Gena without groove from eye to mandible................................................................................................ 2
- Gena with groove from eye to mandible.................................................................................................... 7
2 Metasomal segment II with medial longitudinal impression and posterior notch; premedian transverse carina of metasomal tergite 1 strong, raised and evenly arched (Colombia)...................................................... ............................................................................................ O. atlanticus Fernández & Sarmiento-M., 2002
- Metasomal segment II without medial longitudinal impression and posterior notch; premedian transverse carina strong or weak................................................................................................................................... 3
3 Flagellomere I 1.8 times as long as wide; upper hind edge of eye separated from occipital carina by 1.1 times width of scape (Eastern Australia) ............................................................ O. flavibase Townes, 1977
- Flagellomere I 2.0 to 4.2 times as long as wide; upper hind edge of eye separated from occipital carina by 0.25 to 1.0 times the width of scape............................................................................................................ 4
4 Flagellomere I 2.2 to 2.9 times as long as wide (Madagascar).................................................................... 5
- Flagellomere I 3.0 to 4.2 times as long as wide........................................................................................... 6
5 Vertex with medial impression; apicolateral carina of head with indentation; lamelliform process of propodeum emarginated; male with widened tarsomeres .............................................. O. toliaraensis sp.nov.
- Vertex without a medial impression; apicolateral carina of head without an indentation (male unknown).. ......................................................................................................................................... O. martini sp.nov.
6 Body fuscous; hindfemur of female about 2.5 times as long as high (male unknown) (Ivory Coast).......... ................................................................................................................................. O. majus Townes, 1977
- Body fulvous; hindfemur of female about 4.4 as long as high, of male about 5.5 times as long as high. (Eastern United States and Mexico) ....................................................................... O. banksii (Brues, 1922)
7 Upper hind edge of the eye separated from occipital carina by about 0.3 times width of scape; head and body mostly or entirely fulvous (Mexico-Brazil) ............................................ O. testaceum Cameron, 1887
- Upper hind edge of eye separated from occipital carina by about 1.1 to 2.6 times width of scape; head and body dark brown or blackish, in some specimens thorax fulvoferruginous................................................ 8
8 Tergite I without subbasal transverse carina; propodeum without transverse carina between apicolateral teeth (Eastern Australia) .................................................................................. O. australiae (Perkins, 1908)
- Tergite I with subbasal transverse carina; propodeum with complete or incomplete transverse carina between apicolateral teeth............................................................................................................................ 9
9 Forewing reaching to posterior end of thorax; setae of head and metasoma markedly dense; flagellomere I about 2.6 times as long as wide (South Africa) ................................................... O. saltator (Arnold, 1935)
- Forewing minute or absent, not longer than tegula; setae of head and metasoma moderately dense (but unusually sparse for the genus); flagellomere I segment about 1.4 to 2.2 times as long as wide............. 10
10 Thorax fulvoferruginous; apex of scutellum a rounded 90 ° angle; upper hind edge of eye separated from occipital carina by 1.5 times width of scape; forewing present as small vestige (Zimbabwe)...................... ................................................................................................................ O. myrmosaeforme (Arnold, 1935)
- Thorax reddish brown to blackish; apex of scutellum rounded or subtruncate; upper hind edge of eye separated from the occipital carina by about 2.0 times width of scape; forewing absent (Southeast coast of South Africa) ................................................................................................. O. dentatum (Cameron, 1904)