Key to Nesomyrmex species of Neotropical region

Key to species from Kempf (1959). The species tonsuratus (Kempf) and clavipilis (Wheeler) were not included as they were known only from females.

1 Antennae 12-segmented ... 2 - Antennae 11-segmented ... 10

2 Antennal scapes in repose attaining or surpassing the occipital margin; larger species, thorax length 1.4 mm or more ... 3 - Antennal cales in repose failing to attain the occipital margin; smaller species, thorax length 1.3 mm or less. 5

3 Humeri or pronotum obtusely angulate, almost rounded; petiolar and postpetiolar nodes lacking posterolaterally prominent spines or teeth ... sculptiventris (Mayr) - Humeri or pronotum sharply angulate or even dentate; petiolar and postpetiolar nodes posterolaterally with prominent spines or teeth ... 4

4 Mesonotum laterally projecting as a triangular lobe; thorax strongly constricted in front and behind of this lobe ... pulcher (Emery) - Mesonotum lacking laterally a projecting lobe; thorax feebly constricted in front and behind of mesonotum ... anduzei (Weber)

5 Head above longitudinally costate or rugose ... 6 - Head above without longitudinal costate or rugose ... 9

6 Dorsum of thorax and postpetiole densely punctate with feebly raised longitudinal rugae; lateral lobe of mesonotum blunt; epinotal spines lacking erect or oblique hairs ... itinerans (Kempf) - Dorsum of thorax and postpetiole with strongly raised longitudinal or somewhat vermiculate costae; lateral lobe of mesonotum dentate; epinotal spines with erect or oblique hairs ... 7

7 Basal half of first gastric tergite finely and densely longitudinally striate; lateral border of dorsum of pronotum without a sharp continuous carina ... schwbeli (Forel) - Basal half of first gastric tergite completely smooth and shining; lateral border of dorsum of pronotum a sharp continuous carina ... 8

8 Metasternal lobe dorsally dentate; intervals between costae on thoracic dorsum with miscrosculpture and subopaque ... vicinus (Mayr - Metasternal lobe evenly rounded; intervals between costae on thoracic dorsum smooth and shining ... costatus (Emery)

9 Dorsum of head with numerous shallow foveolae; epinotal spines as long as the distance between their apices ... pittieri (Forel) - Dorsum of head without distinct foveolae; epinotal spines short and subconical, much shorter than the distance between their apices ... brasiliensis (Kempf)

10 Metasternal lobe posterodorsally produced, either angulate or subangulate; antennal scape in repose usually attaining the occipital margin ... 11 - Metasternal lobe posterodorsally not produced, short and evenly rounded; antennal scape in repose failing to attain the occipital margin by a distance equal to its greatest width ... 14

11 Mandibles finely reticulate and subopaque at inner half of upper surface; sides of thorax rather coarsely and irregularly rugose ... 12 - Mandibles smooth and shining at inner half of upper surface; sides of thorax with feeble rugosities or lacking them completely ... 13

12 Sides of petiolar and postpetiolar node with 2-3 prominent teeth, the posteriormost longest; first gastric tergite usually distinctly broader than long ... tristani (Emery) - Sides of petiolar and postpetiolar node usually completely unarmed, never conspicuously armed, at most with a single prominent tooth on petiole; first gastric tergite usually distinctly longer than broad ... asper (Mayr)

13 Frons and vertex of head sculptured and opaque; legs lacking erect hairs ... timidus (Kempf) - Frons and vertex of head smooth and shining; legs with long erect hairs ... pleuriticus (Kempf)

14 Anterior border of pronotum ecarinate; thorax completely smooth and shining ... rutilans (Kempf) - Anterior border of pronotum carinate; thorax always sculptured and opaque ... 15

15 Basal face of epinotum with a flattened, obtuse tooth at each side, separated from and projecting over, the spiracle, which is invisible from above; pronotum almost as long as broad at posterior corner, not conspicuously transverse ... wilda (M. R. Smith) - Basal face of epinotum with a prominent lobe at each side, enclosing posterodorsally the spiracle which is always visible from above; pronotum much broader than long ... 16

16 Antennal scapes and extensor face of tibiae with a few short erect setae; sides of mesonotum broadly rounded and scarcely projecting laterad; epinotal spines very short and straight ... argentinus (Santschi) - Antennal scapes and extensor face of tibiae lacking standing ahirs; sides of mesonotum with a projecting angular or dentate lobe; epinotal spines much longer and curved ... 17

17 Dorsum of head completely reticulate-punctate, longitudinally rugose and opaque; color rather uniformly testaceous or yellowish-brown ... spininodis (Mayr) - Dorsum of head with at least the front and vertex partly smooth and shining; color always darker, at least head and gaster brown to piceous ... echinatinodis (Forel)