Nesomyrmex
Creators: name: Mbanyana, N.
name: Robertson, H. G.
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Formicidae
Nesomyrmex

description: DIAGNOSIS OF WORKERS [Nesomyrmex](IN SOUTHERN AFRICA
Mandibles with five teeth. Clypeus with a projecting median portion that overlaps, and is closely applied to, the mandibular dorsum; either anterior margin of clypeus evenly convex along entire length or lateral portions of clypeus more-or-less transverse and median portion curving sharply outwards to form the projecting lobe. Anterior clypeal margin with a pair of hairs straddling the midline; no median seta present. Antennal scrobes absent. Frontal carinae absent but in some species the frontal lobe is followed by a weak longitudinal striation that runs posteriorly and normally ends before the mid-length of the eyes. Antenna with 12 segments including a three-segmented apical club. Propodeal spiracle circular, situated high up on the side and at about the midlength of the segment. Metanotal groove varying from absent to conspicuously impressed. Propodeum armedorunarmed. Petiolar node variable inshape but generally nodiform. Anterior peduncle with a tooth-like or rounded subpetiolar process.
Superficially, Nesomyrmex workers with a rounded propodeum that lacks spines can be confused with Monomorium, but can be distinguished by lacking the isolated median setae on the anterior clypeal margin. Those species of Nesomyrmex that have the propodeum armed or angulate, superficially resemble Tetramorium species, and can be separated from them mainly bythe lateral portions of clypeus, which are not raised into a narrow ridge or shield-wall in front of the antennal insertions, unlike in Tetramorium. Nesomyrmex can also be confused with Cardiocondyla because the median portion of the clypeus extends over the mandibles in both genera. They are most easily distinguished by the shape of the postpetiole in dorsal view, which in Cardiocondyla is considerably broader than the petiolar node. In addition, the eyes of Cardiocondyla are in front of the midlength of the sides whereas in Nesomyrmex they are at the midlength.
We have placed the Nesomyrmex occurring in southern Africa into two species groups, namely the angulatus-group and simoni-group, which are defined in the first couplet of the key below. Besides the morphological differences between them, they also differ biologically because members of the angulatus-group are arboreal nesters whereas the nests that have been found of simoni-group species have all been in the soil. Almost all the specimens examined for the simoni-group were obtained using ground-trapping methods, mainly pitfalls.
LIST OF SPECIES FROM SOUTHERN AFRICA angulatus species-group
angulatus (Mayr)
denticulatus (Mayr)
stramineus (Arnold)
simoni species-group
antoinetteae sp. nov.
braunsi (Forel)
cederbergensis sp. nov.
entabeni sp. nov.
ezantsi sp. nov.
inye sp. nov.
karooensis sp. nov.
koebergensis sp. nov.
larsenae sp. nov.
mcgregori sp. nov.
nanniae sp. nov.
njengelanga sp. nov.
ruani sp. nov.
saasveldensis sp. nov.
simoni (Emery)
tshiguvhoae sp. nov.
vannoorti sp. nov.
KEY TO SPECIES (WORKERS)
1. Propodeal spines present: long and narrow, in profile distinctly longer than their basal width. Blunt hairs on dorsumofmesosoma. Yellow, tree-nesting species (angulatus-group).. 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 (simoni-group)..4
2. Mesosoma forming a single, uninterrupted flat surface without any trace of metanotal groove. Petiolar node without denticles (Fig. 1a,b). ................................... angulatus
- Mesosoma with promesonotum separated from propodeum by metanotal groove or impression. Petiolar node bearing denticles from which hairs arise (Fig. 1e,h) ................................... 3
3. 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 (Fig. 1d,f) ................................. 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 (Fig. 1g,i) .......................... stramineus
4. Dorsum of petiolar node rugo-reticulate. Rugo-reticulate sculpture is usually also evident partially or completelyonhead and mesosoma (Figs 1j -o; 2a -l) ............................................ 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. Propodeum unarmed. Mesosoma, petiolar node and postpetiole rufous coloured, contrasting with black head and gaster. Larger species (HW> 1.00) (Fig. 1j -l) ..................................... 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. Erect hairs absent on propodeum (Fig. 1m).. simoni
- Erect hairs present on propodeum - at least four pairs.. ..................................... 7
7. Black to dark brown. Strongly-developed rugo-reticulate sculpture on dorsum of head with reticulate cells sharply defined and large - no more than 16 in any one row counted between the eyes (Fig. 2a -c) ................................ 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 (Fig. 2f,i,l) ............... 8
8. 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) (Fig. 2d -f).. ....... koebergensis
- 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. 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) (Fig. 2g -i).. 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) (Fig. 2j -l) ................................... mcgregori
10. 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. Propodeum without erect hairs ................ 12
- Propodeum with erect hairs ................... 15
12 Promesonotum without erect hairs. Propodeum hump-shaped and colour brick red, with gaster dark brown (Fig. 2m) ....................... larsenae
- Promesonotum with erect hairs. Propodeum forming an even convexity and colour uniformly light brown ..................................... 13
13. 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) (Fig. 3a,b)... 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. In dorsal view, metanotal groove clearly defined and with short longitudinal rugulae (Fig. 3e)... entabeni
- In dorsal view, promesonotum and propodeum confluent with no metanotal groove visible medially (Fig. 3h) .. ............................ nanniae
15. In profile, posterior and anterior faces of petiolar node with similar slopes. Colour: head and gaster dark brown, with mesosoma and nodes light brown (Fig. 3j) .. ........................... vannoorti
- In profile, posterior face of petiolar node nearly vertical and much steeper than anterior face. Colour uniformly yellow (Fig. 3m) ...... njengelanga (part)
16. Metapleural gland bulla large and bulging - in dorsal view the sides below the propodeum are convex along their medial length. Colour uniformly dark brown (Fig. 4a,b) ........................ 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. Petiolar node in profile with angulate anterodorsal and posterodorsal angles and with a flat dorsum (Fig. 4d) ........................... karooensis
- Petiolar node in profile with a rounded posterodorsal angle; anterodorsal angle either angulate or rounded; dorsum convex and not clearly defined.. 18
18. Dorsumofhead mainlysmoothandshining,with few longitudinal striations between the eyes (Fig. 4i). ............................... cederbergensis
- Dorsum of head with reticulate sculpture, sometimes verlaid by longitudinal rugulae ................ 19
19. Propodeum angulate but with no clearly defined pair of short triangular teeth. Smaller species (HW 0.507- 0.559) (Figs 3m -o, 4j -l) ....................... 20
description: Published as part of Mbanyana, N. & Robertson, H. G., 2008, Review of the ant genus Nesomyrmex (Hymenoptera: Formicidae: Myrmicinae) in southern Africa., pp. 35-55 in African Natural History 4 on page 35