Key to Odontomachus of the New World

This worker key is based on: Brown, W. L., Jr. 1976c. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section A. Introduction, subtribal characters. Genus Odontomachus. Stud. Entomol. 19:67-171.

This is an older key but will work well for many Odontomachus species. The only species described from the New World since the publication of this key is Odontomachus relictus. This species is endemic to Florida. Some issues regarding a number of North American forms have been discussed, clarified and reclarified in numerous publications since 1976. See - MacGown, J.A., Boudinot, B., Deyrup, M. & Sorger, D.M. 2014. A review of the Nearctic Odontomachus (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males. Zootaxa 3802(4): 515-552 - for the most current treatment of these problems and a review of how these were treated in other publications. There is also a more modern key to the North American species of Odontomachus included in this latest treatment.

Brown noted the following regarding this key:

Before trying the keys, the user should be aware of the special conditions of measurement of this genus, especially for HL and HW (Headlength is measured full-face in the usual way, except that the anterior limit of the head is normally taken as the rounded anterior swellings of the mandibular condyles, which, though not strictly a part of the head proper, nevertheless do complete the outline of the head in front when one or both mandibles are closed (see Figure 2). Headwidth in ants is usually taken across the widest part of the head; in the present genera, the head is widest in the anterior quarter or third, across the eyes and ocular prominences. But the most striking allometric differences among the species affect mainly the posterior half of the head (vertex), which in Odontomachus and Anochetus is slightly to considerably narrower than the width across the eyes. Because the width across the vertex is a more useful character at species level, I have taken HW as the distance between limits of the temporal prominences. In the few difficult cases in which temporal prominences are lacking, HW is taken across that part of the vertex at which the sides are least sharply convergent (most nearly parallel), near or a little behind the midlength of the head (see Figure 2).). Descriptive statements, especially those concerning gastric sculpture and pubescence, are based on clean, unrubbed specimens; dirty or worn specimens can be misleading. These statements also ignore the normal presence of scattered, coarse piligerous punctures on the gastric dorsum in nearly all of the species.

Queens can often be determined using worker characters, but it should be remembered that queens are usually larger than the corresponding workers, and differ from workers by some allometric characters; e. g., queens often have (proportionately) wider vertex, shorter mandibles and antennal scapes, and anteroposteriorly more compressed petiolar node - the nodal form often being strikingly different in the two castes.

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 * Odontomachus
 * Key to US Odontomachus species

1

 * Dorsal surface of head distinctly striate to or nearly to the nuchal carina . . . . . 2


 * Posterior third to half of dorsal surface of head smooth and shining, or nearly so . . . . . 17

2
return to couplet #1
 * 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 . . . . . 3


 * Disc of first gastric segment distinctly and evenly striate over its entire surface, at least as seen from dorsal view . . . . . 15

3
return to couplet #2
 * Mesonotum longitudinally striate (Yucatan Pen. to Vera Cruz and Guatemala) . . . . . Odontomachus yucatecus


 * Mesonotum prevailingly transversely striate . . . . . 4

4
return to couplet #3
 * Head more or less bright red (frontal area often infuscate), contrasting with blackish-brown body and yellow legs; size medium (Costa Rica, to Ecuador W of Andes) . . . . . Odontomachus erythrocephalus


 * Color combination otherwise; if head is distinctly red, then trunk is red also, or legs are dark . . . . . 5

5
return to couplet #4
 * 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 (forests of cis-Andean continental S America from Orinoco Delta to Tucuman, Argentina) . . . . . Odontomachus haematodus


 * Sternum in front of meta thoracic coxae with a low transverse ridge, sometimes notched iri the middle or bilobed, but not produced as acute, paired teeth (gaster smooth or variously sculptured; color varying, but legs usually dark in samples from continental S America) . . . . . 6

6
return to couplet #5
 * Disc of first gastric segment as seen from above very finely, densely and regularly punctulate throughout; opaque or nearly so; longest hairs of gastric dorsum 0.6 mm or more in length; large black or dark brown species (Costa Rica to Colombia) . . . . . Odontomachus opaciventris


 * Disc of first gastric segment otherwise sculptured; shining or, if densely punctulate and opaque, then at least the posterior part becoming longitudinally striate; longest hairs of gastric dorsum < 0.6 mm long . . . . . 7

7
return to couplet #6
 * Disc of first gastric segment very densely punctulate, opaque, longitudinally striate over a posterior portion of variable extent; small species, light to dark brown in color (S Mexico to S Brasil and Bolivia, forests) . . . . . Odontomachus meinerti


 * Disc of first gastric segment prevailingly shining, though its surface sometimes alutaceous, shagreened, or even with traces of striation in the posterior portion . . . . . 8

8
return to couplet #7
 * Head, trunk and petiole nearly or quite concolorous light red or dull yellow; legs yellowish, gaster light brown to blackish . . . . . 9


 * Head, trunk and petiole dark reddish brown or brown to nearly black, legs variable in color, often dark . . . . . 11

9
return to couplet #8
 * Apex of petiole rather suddenly narrowed to a long, slender spine (Cuba, Bahamas, local on Hispaniola) . . . . . Odontomachus insularis


 * Petiole conical or subconical in side view; apex acute or even dentate, but not drawn out into a long, slender spine . . . . . 10

10
return to couplet #9
 * Posterior face of petiole at least feebly concave or sulcate mesad; compound eye usually shorter than maximum W of a mandible (without teeth), rarely slightly longer; sides of head in side view smooth and shining, or, if dull, then the sculpture here not distinctly reticulate-punctulate (Mexico N to S Arizona and C Texas) . . . . . Odontomachus clarus


 * Posterior face of petiole convex in both directions; compound eye distinctly longer than maximum W of a mandible (without teeth); sides of head, especially the part posterior to extraocular furrow, finely, densely and distinctly reticulate-punctulate and dull (known only from types from Pacific Coast of Costa Rica, possibly in mangroves) . . . . . Odontomachus biolleyi

11
return to couplet #8
 * Node of petiole with a pair of prominent posterolateral tumosities at about mid-height; apex as seen from side abruptly narrowed to an axially erect, acute tooth; all surfaces of node smooth or nearly so above basal alutaceous part (Amazon Basin, Guyanas, SE Brasil; forest) . . . . . Odontomachus biumbonatus


 * Node of petiole without paired posterolateral tumosities; or, if moderate swellings are present, the node is distinctly sculptured with horizontal reticulostriation or eostation, or apical spine or tooth inclined caudad from nodal axis . . . . . 12

12
return to couplet #11
 * Antennal scape L > 2.15 mm, or if less than that (in minim workers from incipient nests), then the petiolar node is dome-shaped as seen from the side, with distinctly convex outline front and rear up to root of apical spine . . . . . 13


 * Antennal scape L < 2. 1 5 mm; petiolar node not dome-shaped as seen from the side (widespread in American tropics N to U.S.: Georgia; Cuba and Bermuda) . . . . . Odontomachus brunneus

13
return to couplet #12
 * 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 (E central Peruvian Andes) . . . . . Odontomachus bradleyi


 * Anterior face of petiolar node otherwise formed, either convex, concave or straight from base upward for ½ to 2/3 the distance to the root of the apical tooth or spine; labial palpi 3-merous . . . . . 14

14
return to couplet #13
 * Petiolar node as seen from the side dome-shaped, with at least the anterior outline convex from near base to root of apical tooth (tropical S and C America, Galapagos, W. Indies except Cuba and Bahamas) . . . . . Odontomachus bauri


 * Petiolar node as seen from side gradually tapered dorsad, with basal half to 2/3 of anterior outline concave or straight; grades into form with gaster longitudinally striate above; see couplet 16 ( Panama to NE Mexico) . . . . . Odontomachus laticeps (in part - also )

15
return to couplet #2
 * Striation of gastric dorsum curved-transverse; large, slender species (S Mexico to N Argentina; Trinidad; forest) . . . . . Odontomachus chelifer


 * Striation of gastric dorsum longitudinal . . . . . 16

16
return to couplet #15
 * Mesonotum strongly convex, but broadly sulcate and longitudinally striate on at least the anterior half near midline; appressed pubescence of gastric dorsum nearly obsolete, its individual hairs minute, separated from one another by an average distance of their own length or more (Amazon Basin, Guyanas, forest) . . . . . Odontomachus caelatus


 * Mesonotum gently but evenly convex, transversely striate; reclinate pubescence of gastric dorsum abundant and conspicuous, its individual hairs 2 or more times longer than the average space between them; grades into form with smooth gastric dorsum; see couplet 14 (Panama to NE Mexico) . . . . . Odontomachus laticeps (in part - also )

17
return to couplet #1
 * Ocular prominences each produced anterolaterally into a stout, acute, oblique, toothlike process (W Ecuador) . . . . . Odontomachus cornutus


 * Ocular prominences bluntly rounded, as usual . . . . . 18

18
return to couplet #17
 * Antennal scapes very short, not reaching posterior border of head in full-face view; very small species with broad head (Mato Grosso) . . . . . Odontomachus spissus


 * Antennal scapes surpassing posterior border of head viewed full-face . . . . . 19

19
return to couplet #18
 * Antennal scapes a t least slightly longer than head (SL > HL); slender species, vertex narrow (CI usually under 55) . . . . . 20


 * Antennal scapes shorter than head (SL < HL); more robust species, vertex broader (CI > 55) . . . . . 22

20
return to couplet #19
 * Apex of mandible with only 2 large teeth (intercalary tooth lacking); size small (HL < 2.3 mm; worker characters deduced from queen; W Amazon Basin) . . . . . Odontomachus allolabis


 * Apex of mandible with the usual 3 large teeth, including the intercalary tooth; size larger (HL > 2.4 mm) . . . . . 21

21
return to couplet #20
 * Size very large (HL of holotype worker 4.34 mm); head and body virtually hairless except for a few long hairs on posterior half and underside of gaster; Ecuador: W base of Andes) . . . . . Odontomachus mormo


 * Size not so large (HL < 3.8 mm); head, trunk, petiole and gaster with abundant fine standing hairs; petiolar node pedunculate anteriorly (S Mexico to Bolivia) . . . . . Odontomachus hastatus

22
return to couplet #19
 * Mesepisternum with a prominent, narrowly-rounded anteroventral lobe projecting conspicuously on each side when trunk is viewed from above; medium-sized species (Amazon Basin, Guyanas; forest) . . . . . Odontomachus mayi


 * Mesepisternum with at most a low, inconspicuous convexity on its anteroventral margin; size averaging either larger or smaller than mayi . . . . . 23

23
return to couplet #22
 * Large species (HL > 2.8 mm; SE Brasil) . . . . . Odontomachus affinis


 * Small species (HL < 2.8 mmm; Panama, Costa Rica) . . . . . Odontomachus panamensis