Key to Nesomyrmex species of Neotropical region

Key to Neotropical species of Nesomyrmex based on Kempf (1959). The species Nesomyrmex tonsuratus and Nesomyrmex clavipilis are not included as they are known only from queens.

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 ... Nesomyrmex sculptiventris
 * 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 ... Nesomyrmex pulcher
 * Mesonotum lacking laterally a projecting lobe; thorax feebly constricted in front and behind of mesonotum ... Nesomyrmex anduzei

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 ... Nesomyrmex itinerans
 * 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 ... Nesomyrmex schwebeli
 * 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 ... Nesomyrmex vicinus
 * Metasternal lobe evenly rounded; intervals between costae on thoracic dorsum smooth and shining ... Nesomyrmex costatus

9

 * Dorsum of head with numerous shallow foveolae; epinotal spines as long as the distance between their apices ... Nesomyrmex pittieri
 * Dorsum of head without distinct foveolae; epinotal spines short and subconical, much shorter than the distance between their apices ... Nesomyrmex brasiliensis

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 ... Nesomyrmex asper
 * Mandibles smooth and shining at inner half of upper surface; sides of thorax with feeble rugosities or lacking them completely ... 13

13

 * Frons and vertex of head sculptured and opaque; legs lacking erect hairs ... Nesomyrmex brimodus
 * Frons and vertex of head smooth and shining; legs with long erect hairs ... Nesomyrmex pleuriticus

14

 * Anterior border of pronotum ecarinate; thorax completely smooth and shining ... Nesomyrmex rutilans
 * 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 ... Nesomyrmex wilda
 * 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 ... Nesomyrmex argentinus
 * 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 ... Nesomyrmex spininodis
 * 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 ... Nesomyrmex echinatinodis