1	Petiole pedunculate to subpedunculate, in lateral view the anterodorsal margin of the gaster forms a single convexity that ascends posterad at approximately 45° (Fig. 1A)	2
–	Petiole sessile, not subpendunculate, in lateral view the anterodorsal margin of the first gaster segment forming a much steeper slope (>45°) with a more or less distinct vertical anterior face (Fig. 1B)	4
2	Dorsal surface of the head with deep striation that reaches to the nuchal collar; color uniform ferruginous to dark red	O. davidsoni sp. nov.
–	Posterior third to half of dorsal surface of head smooth and shining; color variable	3
3	Without metasternal process; mesonotum almost hairless; larger body size (HL > 4 mm). Ground living	O. mormo
–	With metasternal process; dorsal surface of mesonotum covered in small erect setae; smaller body size (HL < 3.8 mm). Arboreal	O. hastatus
4	Dorsal surface of head distinctly striate to or nearly to the nuchal carina	5
–	Posterior third to half of dorsal surface of head smooth and shining, or nearly so	22
5	Disc (dorsal surface) of first gastric segment predominantly smooth, punctulate, alutaceous, or reticulate; striation absent, or if present, mixed with other sculpture and distinct only on the posterior half of the disc	6
–	Disc of first gastric segment distinctly and evenly striate over its entire surface, at least as seen from dorsal view	17
6	Mesonotum longitudinally striate	O. yucatecus Brown, 1976
–	Mesonotum prevailingly transversely striate	8
7	Head more or less bright red (frontal area often infuscate), contrasting with blackish-brown body and yellow legs; size medium	O. erythrocephalus
–	Color combination otherwise; if head is distinctly red, then trunk is red also, or legs are dark	8
8	Sternum immediately in front of and between metathoracic coxae produced as a slender, acute pair of teeth or spines; disc of first gastric segment densely and finely shagreened and pubescent, usually opaque; body brown, legs yellow to brown	O. haematodus (Linnaeus, 1758)
–	Sternum in front of metathoracic coxae with a low transverse ridge, sometimes notched in the middle or bilobed, but not produced as acute, paired teeth	9
9	Petiole predominantly smooth and shiny, with the anterior border erected or slightly convex, and the apex produced into a large spine with posterior orientation; head, mesosoma and petiole with a clear red coloration and the gaster dark brown	O. insularis Guérin-Méneville, 1844
–	Petiole differently shapes, color combination varies	10
10	Anterior face of petiolar node as seen from the side rising steeply from anterior margin, then passing through an obtuse angle into a long section concave in outline to the root of the apical spine; labial palpi 4-merous	O. bradleyi Brown, 1976
–	Petiole differently shaped	11
11	Metasternal process like an arc with or without middle division; petiole smooth or a little striate, with both the anterior and posterior margin convex; the petiolar spine forms gradually, without clear distinction from petiole	O. cf. brunneus Patton, 1894 (possibly Odontomachus ruginodis; O. brunneus is apparently restricted to southeastern US. The status of the Central and South American populations comparable with O. brunneus need to be established.)
–	Metasternal process absent, bilobed or triangular; petiole differently shapes or if both sides convex, with a clear differentiation of the spine from the rest of the petiole	12
12	Metasternal process absent	13
–	Metasternal process bilobed or triangular	14
13	Black coloration; Node of petiole with a pair of prominent posterolateral tumosities at about mid-height and without striation; apex as seen from side abruptly narrowed to an axially erect, acute tooth	O. biumbonatus Brown, 1976
–	Node of petiole without paired posterolateral tumosities; Posterior face of petiole less concave, with short petiolar spine (0.1 mm)	O. clarus Roger, 1861
14	Anterior margin of petiole at least weakly convex	15
–	Anterior margin of petiole basal of the node concave or straight	16
15	Metasternal process completely bilobed; color generally dark	O. bauri Emery, 1892
–	Metasternal process formed by an obtuse wide lobe followed by a transverse flange which is produced into a triangular process; usually light color	O. biolleyi Forel, 1809
16	Petiole strongly transversely striate, with a clearly differentiated spine; small species (TL 8.6–9.35 mm)	O. ruginodis Smith, 1937
–	Petiole without or only weak striation and with spine not clearly differentiated from the petiole; large species (TL 12 mm)	O. laticeps Roger, 1861
17	First gaster segment with only one type of sculpture, which is either punctulate or striate	18
–	First gaster segment with a combination of punctulate and reticulate sculpture	21
18	First gaster segment punctulate on its entire surface	O. opaciventris Forel, 1899
–	First gaster segment striate on most of its surface, at least in dorsal view	19
19	Transverse striation patterns on the gaster; large and slender	O. chelifer (Latreille, 1802)
–	Longitudinal striation on the dorsal gaster surface	20
20	Mesonotum strongly convex, but broadly sulcate and longitudinally striate on at least the anterior half near midline	O. caelatus Brown, 1976
–	Mesonotum gently but evenly convex, transversely striate	O. laticeps
21	Mesonotum with longitudinal striation	O. scalptus Brown, 1978
–	Mesonotum with transverse striation	O. meinerti Forel, 1805
22	Ocular prominences each produced anterolaterally into a stout, acute, oblique, toothlike process	O. cornutus Stitz, 1933
–	Ocular prominences bluntly rounded, as usual	24
23	Antennal scapes very short, not reaching posterior border of head in full-face view; very small species with broad head	O. spissus Kempf, 1962
–	Antennal scapes surpassing posterior border of head viewed full-face	24
24	Apex of mandible with only 2 large teeth (intercalary tooth lacking)	O. allolabis Kempf, 1974
–	Apex of mandible with 3 teeth	25
25	Mesepisternum with a prominent, narrowly rounded anteroventral lobe projecting conspicuously on each side when trunk is viewed from above	O. mayi Mann, 1912
–	Mesepisternum with at most a low, inconspicuous convexity on its anteroventral margin	26
26	Petiole clearly differentiated spine; larger species (HL > 2.8 mm)	O. affinis Guérin-Méneville, 1844
–	Both faces of petiole converge into a thick spine that is flattened laterally; smaller species (HL < 2.8 mm)	O. panamensis Forel, 1899