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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 HNS workers with a rounded propodeum that lacks spines can be confused with Monomorium HNS , but can be distinguished by lacking the isolated median setae on the anterior clypeal margin. Those species of Nesomyrmex HNS that have the propodeum armed or angulate, superficially resemble Tetramorium HNS 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 HNS . Nesomyrmex HNS can also be confused with Cardiocondyla HNS 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 HNS is considerably broader than the petiolar node. In addition, the eyes of Cardiocondyla HNS are in front of the midlength of the sides whereas in Nesomyrmex HNS they are at the midlength.
We have placed the Nesomyrmex HNS 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.