Key to Colombian Nesomyrmex species

Key to Colombian Nesomyrmex species based on workers (adapted and modified from Kempf (1959) by Arredondo & Guerrero (2025)).

1

Antenna with 12 antennomeres => 2
Antenna with 11 antennomeres => 9

2

return to couplet #1

Antennal scape in repose reaching or surpassing the occipital margin (SI > 82) (Fig. 4A). In dorsal view, humerus (ha) distinctly dentate (Fig. 5A). Mesosoma length (= WL) greater than or equal 1.4 mm => 3
Antennal scape in repose failing to reach the occipital margin (SI < 81) (Fig. 4B). In dorsal view, humerus (ha) distinctly angled (Fig. 5B), Slightly angled (Fig. 5C) or rounded (Fig. 5D). Mesosoma length (= WL) less than or equal 1.3 mm => 4

Arredondo & Guerrero (2025), Fig. 4. Relative length of antennal scapes. A, scape in repose reaching or surpassing the occipital margin. B, scape in repose failing to reach the occipital margin.
Arredondo & Guerrero (2025), Fig. 5. Humerus shape (dorsal view). A, dentate. B, strongly angled. C, slightly angled. D, rounded.

3

return to couplet #2

In dorsal view, lateral mesonotum process (lmsp) dentate (Fig. 6A). Lateral margins of the mesosoma constricted anteriorly and posteriorly to the mesonotal projection => Nesomyrmex pulcher (species probably present in Colombia)
In dorsal view, mesonotum lacking lateral projections, sometimes rounded or slightly rounded margins (Fig. 6B). Lateral margins of mesonotum weakly constricted anteriorly and posteriorly to mesonotum => Nesomyrmex anduzei

Arredondo & Guerrero (2025), Fig. 6. Mesonotal lateral projection. A, triangular lobe-shaped. B, rounded or slightly rounded lobe-shaped. White arrows indicate anterior and posterior constrictions to the lateral projection of the mesonotum.

4

return to couplet #2

Dorsal surface of the head longitudinally costate (Fig. 7A) or rugose (Fig. 7B) => 5
Dorsal surface of the head foveate (Fig. 7C), or smooth and shiny (Fig. 7D) => 7

5

return to couplet #4

Frontal lobe projected laterally (widest posterior to torulus) (Fig. 8A), covering the antennal insertions. In dorsal view, lateral projection of the mesonotum dentate (lmsp) (Fig. 9A). Lateral dorsopropodeal processes (ldpp) long, covering propodeal spiracle in dorsal view (Fig. 9A). Dorsal surface of mesosoma and postpetiole with longitudinal costae strongly elevated => Nesomyrmex xerophilus
Frontal lobes without lateral projection, antennal insertions partially exposed (Fig. 8B). In dorsal view, lateral projection of the mesonotum blunt (lmsp) (Fig. 9B). Lateral dorsopropodeal processes (ldpp) short, not covering spiracle in dorsal view (Fig. 9B). Dorsal surface of mesosoma and postpetiole with weakly elevated longitudinal roughness => 6

6

return to couplet #5

In lateral view, mesosomal profile straight (Fig. 10A). In dorsal view, humerus (ha) strongly angled (Fig. 5B) => Nesomyrmex iku
In lateral view, mesosomal profile convex (Fig. 10B). In dorsal view, humerus (ha) slightly angulated (Fig. 5C) => Nesomyrmex itinerans

7

return to couplet #4

Dorsal surface of the head smooth and shiny (Fig. 7D). Head length > 1.1 ×mesosoma length. Anterior margin of pronotum without carina (Fig. 11A). Postpetiolar node smooth and shiny => Nesomyrmex tonsuratus
Dorsal surface of the head foveate, or weakly foveated (Fig. 7C). Head length smaller than mesosoma length. Anterior margin of pronotum carinate (Fig. 11B). Postpetiolar node sculpted and matte => 8

Arredondo & Guerrero (2025), Fig. 7. Types of sculpture. A, costate. B, rugose. C, foveate. D, smooth.

8

return to couplet #7

Dorsal surface of the head foveate. Antennal scape curved at its base. Propodeal spines as long as the distance between their apices => Nesomyrmex pittieri
Dorsal surface of the head weakly foveated. Antennal scape straight at its base. Propodeal spines short and subconical, much shorter than the distance between their apices => Nesomyrmex brasiliensis (species probably present in Colombia)

9

return to couplet #1

Antennal scape in repose reaching or surpassing the occipital margin (S > 82) (Fig. 4A). Propodeal lobe (pl) angulate, apex blunt (Fig. 12A) => 10
Antennal scape barely reaching the occipital margin by a distance equal to its greatest width (SI < 81) (Fig. 4B). Propodeal lobe (pl) short and uniformly rounded (Fig. 12B) => 13

Arredondo & Guerrero (2025), Fig. 4. Relative length of antennal scapes. A, scape in repose reaching or surpassing the occipital margin. B, scape in repose failing to reach the occipital margin.
Arredondo & Guerrero (2025), Fig. 12. Propodeal lobe shape. A, angulate, apex blunt. B, short, uniformly rounded.

10

return to couplet #9

Inner area of the dorsal surface of the mandibles finely imbricate and subopaque (Fig. 13A). Sides of the mesosoma roughly sculptured => Nesomyrmex asper
Inner area of the dorsal surface of the mandible smooth and shiny (Fig. 13B). Sides of the mesosoma smooth, with little or no roughness => 11

Arredondo & Guerrero (2025), Fig. 13. Medial area of the dorsal surface of the mandible, photomicrography and electron micrography. A, reticulated and opaque. B, smooth and shiny. White box is a close-up to observe the detail of the sculpture in question.

11

return to couplet #10

Dorsal surface of the head rugose (Fig. 7B), matte sculpture. Legs lacking erect hairs (Fig. 14A) => Nesomyrmex brimodus (species probably present in Colombia)
Dorsal surface of the head smooth and shiny (Fig. 7D). Legs with long erect hairs (Fig. 14B) => 12

Arredondo & Guerrero (2025), Fig. 7. Types of sculpture. A, costate. B, rugose. C, foveate. D, smooth.
Arredondo & Guerrero (2025), Fig. 14. Leg pilosity. A, without presence of pilosity. B, with long erect or suberect hairs.

12

return to couplet #11

Anterior margin of pronotum straight (Fig. 15A). Sculpture of mesosoma dorsum opaque and strongly marked, with reticulate microsculpture. Sides of mesosoma with variable sculpture, but never longitudinally striate => Nesomyrmex pleuriticus
Anterior margin of pronotum convex (Fig. 15B). Sculpture of dorsum of mesosoma partially smooth and shiny, with weakly marked longitudinal striae. Sides of mesosoma with longitudinal striations => Nesomyrmex vargasi

Arredondo & Guerrero (2025), Fig. 15. Anterior margin of pronotum. A, straight. B, convex.

13

return to couplet #9

Dorsal surface of the head smooth and shiny. Mesosoma with weakly marked longitudinal striation. First tergite gastral without sculpture, completely smooth and shining (Fig. 16A). Coloration uniformly pale yellow => Nesomyrmex konina
Dorsal surface of the head with sculpture, partly or completely rugose. Mesosoma with marked longitudinal striation. First gastral tergite with variable sculpture (Fig. 16B). Testaceous or yellowish brown to dark brown coloration => 14

Arredondo & Guerrero (2025), Fig. 16. Sculpting of the first gastral tergite. A, smooth. B, sculpted. The inset square corresponds to an enlargement of the dorsal surface of the first gastral tergum.

14

return to couplet #13

In full-face view, front and vertex opaque, finely reticule-punctate and longitudinally rugose, without shining areas (Fig. 17A). Coloration concolor, testaceous or yellowish-brown. First gastric tergite usually more sharply aciculate-striate on the anterior half gastric tergite => Nesomyrmex spininodis
In full-face view, front and vertex partly or completely smooth and shiny (Fig. 17B). Color always darker, at least head and gaster brown to black. First gastric tergite very lightly sculptured => Nesomyrmex echinatinodis

Arredondo & Guerrero (2025), Fig. 17. Sculpting of front and vertex (full-face view). A, finely reticulate-punctate and longitudinally rugose, without shining areas. B, partly or completely smooth and shining. White box is a close-up to observe the detail of the sculpture in question.

References