Key to Nesomyrmex of southern Africa

This worker key covers all the species present in South Africa, and is based on: [[Media:Mbanyana N Robertson H 2008.pdf|Mbanyana, N. and Robertson, H.G. 2008. Review of the ant genus Nesomyrmex in southern Africa. African Natural History 4: 35-55 PDF]]

The species present in the Afrotropical Region but are not present here are: Nesomyrmex cataulacoides, Nesomyrmex evelynae, Nesomyrmex grisoni, Nesomyrmex humerosus, Nesomyrmex innocens and Nesomyrmex madecassus.

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Nesomyrmex

1

 * Propodeal spines present: long and narrow, in profile distinctly longer than their basal width. Blunt hairs on dorsum of mesosoma. Yellow, tree-nesting species . . . . . 2
 * Propodeal spines present or absent; if present, short and broad: in profile as long as or shorter than their basal width. Hairs on dorsum of mesosoma tapering or, rarely, blunt. Ground nesting species, variable in colour . . . . . 4

2
return to couplet #1
 * Mesosoma forming a single, uninterrupted flat surface without any trace of metanotal groove. Petiolar node without denticles . . . . . Nesomyrmex angulatus
 * Mesosoma with promesonotum separated from propodeum by metanotal groove or impression. Petiolar node bearing denticles from which hairs arise . . . . . 3

3
return to couplet #2
 * Subpetiolar process with a tooth anteriorly followed by a long cuticular flange, which runs back to the postpetiolar junction. Large species: HW 0.629–0.757, HL 0.828–0.921, EL 0.177–0.216 . . . . . Nesomyrmex denticulatus
 * Subpetiolar process an anteriorly situated simple rounded tooth or a denticle. Smaller species: HW 0.502–0.525; HL 0.612–0.618, EL 0.128–0.138 . . . . . Nesomyrmex stramineus

4
return to couplet #1
 * Dorsum of petiolar node rugo-reticulate. Rugoreticulate sculpture is usually also evident partially or completely on head and mesosoma . . . . . 5
 * Rugo-reticulate sculpture absent from head, mesosoma and petiolar node. These surfaces either smooth, with longitudinal striations, with transverse rugulae or with fine reticulate sculpture . . . . . 10

5
return to couplet #4
 * Propodeum unarmed. Mesosoma, petiolar node and postpetiole rufous coloured, contrasting with black head and gaster. Larger species . . . . . Nesomyrmex braunsi
 * Propodeum armed with a pair of short spines or teeth. Uniformly coloured with no obviously contrasting body parts. Smaller species (HW < 1.00) . . . . . 6

6
return to couplet #5
 * Erect hairs absent on propodeum . . . . . Nesomyrmex simoni
 * Erect hairs present on propodeum – at least four pairs . . . . . 7

7
return to couplet #6
 * Black to dark brown. Strongly-developed rugoreticulate sculpture on dorsum of head with reticulate cells sharply defined and large – no more than 16 in any one row counted between the eyes . . . . . Nesomyrmex saasveldensis
 * Yellow to medium brown species. Rugo-reticulate sculpture on head present or absent. If present, weakly developed with small reticulate cells between eyes not all clearly distinguishable and total more than 20 in any one row . . . . . 8

8
return to couplet #7
 * Anterior clypeal margin only slightly concave laterally, so that the median portion is not clearly defined from the lateral portions. Smaller (HL 0.813–0.902; PW 0.443–0.492) . . . . . Nesomyrmex koebergensis (in part)
 * Anterior clypeal margin strongly concave laterally so that the median portion is clearly defined from the lateral portions and appears as a shelf over the mandibles. Larger (HL 0.993–1.101; PW 0.577– 0.680) . . . . . 9

9
return to couplet #8
 * Dorsum of head entirely covered by longitudinal rugulae. Propodeum armed with broad triangular teeth, the angle formed by each tooth being nearly 90 degrees. Head narrower (CI 74–79) and scapes relatively longer (SI 101–107) . . . . . Nesomyrmex antoinetteae
 * Median portion of head dorsum not covered by longitudinal rugulae, only smooth or with reticulate ground sculpture. Propodeum armed with acute spines, the angle formed by each tooth being much less than 90 degrees. Head broader (CI 83–84) and scapes relatively shorter (SI 87–88) . . . . . Nesomyrmex mcgregori

10
return to couplet #4
 * Propodeum unarmed and in profile rounding smoothly from dorsum into declivity, not at all angulate. Declivity without a lateral margin . . . . . 11
 * Propodeum armed with a pair of short spines or small triangular teeth or in profile angulate (sometimes very slightly) between dorsum and declivity. If propodeum is angulate, then declivity with a lateral margin . . . . . 16

11
return to couplet #10
 * Propodeum without erect hairs . . . . . 12
 * Propodeum with erect hairs . . . . . 15

12
return to couplet #11
 * Promesonotum without erect hairs. Propodeum hump-shaped and colour brick red, with gaster dark brown . . . . . Nesomyrmex larsenae
 * Promesonotum with erect hairs. Propodeum forming an even convexity and colour uniformly light brown . . . . . 13

13
return to couplet #12
 * Sides of petiolar node completely covered with strong, sometimes irregular, rugulae. In dorsal view the entire node with continuous rugulae around it. Large species (HW 0.644–0.690) . . . . . Nesomyrmex ruani
 * Sides of petiolar node with punctulate ground sculpture or at most with a few weak rugulae. In dorsal view these feeble rugulae may persist, may fade out, or may be replaced entirely with reticulate-punctate sculpture but in no case does the entire node appear to be encircled with strong rugulae everywhere. Small species (HW 0.497–0.590) . . . . . 14

14
return to couplet #13
 * In dorsal view, metanotal groove clearly defined and with short longitudinal rugulae . . . . . Nesomyrmex entabeni
 * In dorsal view, promesonotum and propodeum confluent with no metanotal groove visible medially . . . . . Nesomyrmex nanniae

15
return to couplet #11
 * In profile, posterior and anterior faces of petiolar node with similar slopes. Colour: head and gaster dark brown, with mesosoma and nodes light brown . . . . . Nesomyrmex vannoorti
 * In profile, posterior face of petiolar node nearly vertical and much steeper than anterior face. Colour uniformly yellow . . . . . Nesomyrmex njengelanga (in part)

16
return to couplet #10
 * Metapleural gland bulla large and bulging – in dorsal view the sides below the propodeum are convex along their medial length. Colour uniformly dark brown . . . . . ''Nesomyrmex tshiguvhoae
 * Metapleural gland bulla not as prominent – in dorsal view the sides below the propodeum are more-or-less straight along their medial length. Colour uniformly yellow or light brown . . . . . 17

17
return to couplet #16
 * Petiolar node in profile with angulate anterodorsal and posterodorsal angles and with a flat dorsum . . . . . Nesomyrmex karooensis
 * Petiolar node in profile with a rounded posterodorsal angle; anterodorsal angle either angulate or rounded; dorsum convex and not clearly defined . . . . . 18

18
return to couplet #17
 * Dorsum of head mainly smooth and shining, with few longitudinal striations between the eyes . . . . . Nesomyrmex cederbergensis
 * Dorsum of head with reticulate sculpture, sometimes verlaid by longitudinal rugulae . . . . . 19

19
return to couplet #17
 * Propodeum angulate but with no clearly defined pair of short triangular teeth. Smaller species (HW 0.507– 0.559) . . . . . 20
 * Propodeum armed with a pair of short triangular teeth. Larger species (HW 0.598–0.718) . . . . . 21

20
return to couplet #19
 * Long curved hairs present on the ventral surface of head. Promesonotal dorsum with reticulate ground sculpture overlaid by longitudinal rugulae. Eyes with 12 ommatidia in a longest row. Colour medium brown . . . . . Nesomyrmex inye
 * Long curved hairs absent from ventral surface of head, only straight hairs present. Promesonotal dorsum with fine reticulate sculpture and short rugulae along the metanotal groove. Eyes with 10–11 ommatidia in a longest row. Colour uniformly yellow . . . . . Nesomyrmex njengelanga (in part)

21
return to couplet #19
 * Dorsum of head with reticulate sculpture overlaid by longitudinal rugulae. Yellow to light brown species . . . . . Nesomyrmex koebergensis (in part)
 * Dorsum of head predominantly smooth, with fine reticulate ground sculpture. Pale species . . . . . Nesomyrmex ezantsi