Nesomyrmex humerosus

N. humerosus is known to occur in Kenya, Tanzania and Yemen. It is a rather rarely collected species and our scarce knowledge is based on just four collection events. Based on a sample collected in Kenya by the first author, it seems to live on vegetation, but it was also sampled from the ground in Tanzania and Yemen. It is possible that the species also occurs in other East African countries, such as Somalia and Mozambique, which are greatly under-sampled. (Hita Garcia et al 2017)

Identification
A member of the humerosus species-group. This very distinctive species is easily separable from all other known African forms by its flat-margined clypeal lobe, deep metanotal groove, large eyes, sharply marginate pronotum with dentate corners and sharply triangular petiole node. (Bolton 1982)

Sharaf et al. (2017)  Arabian Peninsula - The following character combination distinguishes N. humerosus from the other members of the group in the Arabian Peninsula: anterior clypeal lobe short, flat-margined, and never convex, with small median triangular projection; clypeus without median longitudinal carina; pronotum anterodorsally sharply marginate, with sharp, dentate corners; in profile mesosomal outline conspicuously concave; petiole barrel-shaped with very weakly developed, short and triangular petiolar node.

Distribution based on Regional Taxon Lists
Afrotropical Region: Kenya, United Republic of Tanzania, Yemen.

Nomenclature

 *  humerosus. Leptothorax (Goniothorax) humerosus Emery, 1896g: 62 (w.) EAST AFRICA (no locality given, probably KENYA). Combination in Nesomyrmex: Bolton, 2003: 272. See also: Bolton, 1982: 329.

Worker
Sharaf et al. (2017) - (n=3). HL 0.74–0.75; HW 0.70–0.71; SL 0.58–0.59; EL 0.27–0.28; PH 0.34–0.35; PW 0.52–0.53; WL 0.89–0.92; PSL 0.19–0.20; PTL 0.12–0.13; PTH 0.24–0.25; PTW 0.21–0.22; PPL 0.15–0.16; PPH 0.21–0.22; PPW 0.33–0.34; OI 39; SI 83; CI 95; DMI 58; LMI 38; PSLI 26–27; LPeI 50–52; DPeI 169–175; LPpI 71–73; DPpI 213–220; PPI 155–157.

Bolton (1982) - TL 3.7, HL 0.90, HW 0.75, CI 83, SL 0.64, SI 85, PW 0.52, AL 0.98

Mandibles almost smooth, with only vestigial traces of superficial sculpture. Median lobe of clypeus strongly produced, roughly rectangular, its anterior margin transverse and flat; the anterior margin meeting the sides of the lobe in a distinct angle. Median clypeal carina absent. Narrow weakly differentiated frontal carinae present which are scarcely stronger than the remaining cephalic sculpture but which reach back well beyond the level of the posterior margins of the eyes. Antennal scrobes absent. Antennal scapes moderately long, SI 85. Maximum diameter of eye 0.24, about 0.32 x HW and with 14-15 ommatidia in the longest row. With the head in full-face view the sides narrower in front of the eyes than behind and somewhat convergent anteriorly. Sides behind eyes rounding evenly into the occipital margin, the latter shallowly and evenly transversely convex. Pronotum sharply marginate laterally, the anterior pronotal corners dentate. With the alitrunk in profile the promesonotum convex, the metanotal groove deeply impressed. Propodeum broadly and evenly convex in profile, sloping down posteriorly to the long spines; the latter blunt apically and with their dorsal margins angled. Metapleural lobes low and rounded. Petiole in profile with the node triangular, rising to an acute peak above; anterior peduncle of petiole short. In dorsal view the sides of the petiole roughly parallel. Postpetiole much broader than petiole. Basal face of first gastral tergite transverse except for a median concavity where it articulates with the postpetiole. Dorsum of head everywhere sculptured with fine longitudinal rugulae and with a fine granular to punctulate superficial ground-sculpture. Dorsal alitrunk with ground-sculpture similar to head. Pronotum also with 7-8 broad, coarse longitudinal rugae which are almost sulcate in appearance and are most strongly developed anteriorly. These longitudinal rugae are continuous over the length of the promesonotum and also traverse the base of the metanotal groove, but they either fade out or become very weakly defined on the propodeum where a punctulate ground-sculpture predominates. Petiole and postpetiole finely and densely reticulate-punctulate, the first gastral tergite very densely finely shagreened and opaque. All dorsal surfaces of head and body with distinctive short stout blunt hairs. Body colour more or less uniform medium brown but the mandibles, clypeallobe and antennae yellow. Propodeal spines yellowish, lighter in colour than the propodeum itself.

References based on Global Ant Biodiversity Informatics

 * Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
 * Hita Garcia F., Mbanyana N., Audisio T. L., and G. D. Alpert. 2017. Taxonomy of the ant genus Nesomyrmex Wheeler (Formicidae, Myrmicinae) in the Afrotropical region, with a review of current species groups and description of a new species of the N. angulatus group from Mozambique. European Journal of Taxonomy 258: 1–31.
 * IZIKO South Africa Museum Collection
 * Sharaf M.R., S. A. Akbar, A. S. Aldawood, and F. Hita Garcia. 2017. Review of the ant genus Nesomyrmex Wheeler, 1910 (Hymenoptera, Formicidae, Myrmicinae) from the Arabian Peninsula. African Invertebrates 58(2): 21–37.