Nesomyrmex species groups of the Afrotropical and Malagasy regions

The following is based on [[Media:Csosz & Fisher, 2015.pdf |Csösz, S. and Fisher, B.L. 2015. Diagnostic survey of Malagasy Nesomyrmex species-groups and revision of hafahafa group species via morphology based cluster delimitation protocol. ZooKeys. 526:19-59. PDF]].

The present work (2015) is the beginnings of a comprehensive revision of the genus for the Malagasy region. More species descriptions of known new species are needed.

There is a Key to the Nesomyrmex species groups of the Malagasy region

N. angulatus species-group
Nesomyrmex angulatus

Pronotal spines present or absent. Anterodorsal spines on petiolar node absent. Propodeal spines short to long and acute. Vertex ground sculpture areolate. Main sculpture on vertex not defined. Metanotal depression present or absent. Median clypeal notch present or absent. Median clypeal notch shape/depth: 0–23 μm. Antennomere count: 12. Absolute cephalic size (CS): 591 μm [418, 946]. Cephalic length vs. maximum width of head capsule (CL/CWb): 1.218 [1.057, 1.490]. Postocular distance vs. cephalic length (PoOc/CL): 0.40 [0.359, 0.444]. Scape length vs. absolute cephalic size (SL/CS): 0.676 [0.519, 0.866]. Eye length vs. absolute cephalic size (EL/CS): 0.260 [0.193, 0.317]. Petiole width vs. absolute cephalic size (PEW/CS): 0.431 [0.330, 0.522]. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.496 [0.361, 0.585]. Petiolar node height vs. absolute cephalic size (PEW/CS): 0.250 [0.185, 0.311]. Nesomyrmex angulatus (Mayr, 1862) and ca. four undescribed species belong to this group in the Malagasy zoogeographical region.

N. hafahafa species-group

 * Nesomyrmex capricornis
 * Nesomyrmex hafahafa
 * Nesomyrmex medusus
 * Nesomyrmex spinosus

Key to Nesomyrmex hafahafa group species

The three pairs of dorsal spines (pronotal spines, propodeal spines and antero-dorsal spines on petiolar node) makes the appearance of this group extremely unique; no similar species group has been found either in the Malagasy region or on the African continent.

Pronotal spines present. Anterodorsal spines on petiolar node present. Propodeal spines long and acute. Vertex ground sculpture areolate. Vertex main sculpture rugulose. metanotal depression absent. Median clypeal notch present. Median clypeal notch shape/depth: 15–31 μm. Antennomere count: 12. Absolute cephalic size (CS): 1059 μm [930, 1200]. Cephalic length vs. maximum width of head capsule (CL/CWb): 1.074 [1.0, 1.143]. Postocular distance vs. cephalic length (PoOc/CL): 0.378 [0.342, 0.403]. Scape length vs. absolute cephalic size (SL/CS): 0.890 [0.835, 0.984]. Eye length vs. absolute cephalic size (EL/CS): 0.232 [0.210, 0.264]. Petiole width vs. absolute cephalic size (PEW/CS): 0.267 [0.203, 0.353]. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.523 [0.430, 0.586]. Petiolar node height vs. absolute cephalic size (PEW/CS): 0.142 [0.107, 0.186]. Four species, Nesomyrmex capricornis sp. n., N. hafahafa sp. n., N. medusus sp. n. and N. spinosus sp. n. are known to constitute this species group in Madagascar.

N. madecassus species-group

 * Nesomyrmex gibber
 * Nesomyrmex madecassus

Pronotal spines absent. Anterodorsal spines on petiolar node absent. Propodeal spines short, lamelliform to absent. Vertex ground sculpture smooth. Vertex main sculpture not defined. Metanotal depression present. Median clypeal notch present or absent. Median clypeal notch shape/depth 0–15 μm. Antennomere count: 12. Absolute cephalic size (CS): 571 μm [405, 785]. Cephalic length vs. maximum width of head capsule (CL/CWb): 1.231 [1.092, 1.567]. Postocular distance vs. cephalic length (PoOc/ CL): 0.479 [0.407, 0.544]. Scape length vs. absolute cephalic size (SL/CS): 0.718 [0.492, 0.831]. Eye length vs. absolute cephalic size (EL/CS): 0.249 [0.1934, 0.279]. Petiole width vs. absolute cephalic size (PEW/CS): 0.217 [0.181, 0.256]. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.331 [0.243, 0.398]. Petiolar node height vs. absolute cephalic size (PEW/CS): 0.122 [0.072, 0.158]. Nesomyrmex madecassus (Forel, 1892) and ca. seven other taxa from the Malagasy zoogeographical region will be revised in the forthcoming revisionary work.

N. sikorai species-group
Nesomyrmex retusispinosus Nesomyrmex sikorai

Pronotal spines present or absent. Anterodorsal spines on petiolar node absent. Propodeal spines short to long and acute. Vertex ground sculpture not defined. Vertex main sculpture areolate. Metanotal depression present. Median clypeal notch present or absent. Median clypeal notch shape/depth 0–15 μm. Antennomere count: 12. Absolute cephalic size (CS): 750 μm [634, 890]. Cephalic length vs. maximum width of head capsule (CL/CWb): 1.218 [1.075, 1.382]. Postocular distance vs. cephalic length (PoOc/CL): 0.461 [0.411, 0.511]. Scape length vs. absolute cephalic size (SL/CS): 0.816 [0.761, 0.872]. Eye length vs. absolute cephalic size (EL/CS): 0.232 [0.201, 0.284]. Petiole width vs. absolute cephalic size (PEW/CS): 0.243 [0.206, 0.326]. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.359 [0.306, 0.426]. Petiolar node height vs. absolute cephalic size (PEW/CS): 0.175 [0.149, 0.205]. Nesomyrmex sikorai (Emery, 1896), Nesomyrmex retusispinosus (Forel, 1892) plus ca. ten more Malagasy species will be revised in a forthcoming revisionary work.