Nesomyrmex larsenae

Two specimens were collected from pitfall traps and one specimen from sweeping vegetation in Succulent Karoo near Nieuwoudtville in the Northern Cape. Probably ground-nesting but sweep sample shows that it does forage in vegetation.

Identification
Mbanyana and Robertson (2008) - Among the species without hairs on the propodeum (Nesomyrmex larsenae, Nesomyrmex ruani, Nesomyrmex entabeni and Nesomyrmex nanniae), N. larsenae is distinguished by lacking erect hairs on the promesonotum, and also distinguished by its hump-shaped propodeum and by the brick red colour, with gaster dark brown; the other three species have erect hairs on the promesonotum, the propodeum forms an even convexity (not hump-shaped), and their colour is uniformly medium brown.

Key to Nesomyrmex of southern Africa

Distribution based on Regional Taxon Lists
Afrotropical Region: South Africa.

Nomenclature

 *  larsenae. Nesomyrmex larsenae Mbanyana & Robertson, 2008: 48, figs. 2m-o (w.) SOUTH AFRICA.

Worker
Holotype. HL 0.698, HW 0.529, HW1 0.562, CI 76, SL 0.443, SI 84, PW 0.418, ML 0.861, EL 0.197, EI 37.

Mandibles with fine longitudinal striations. Clypeus predominantly smooth, with weak longitudinal striations. Entire anterior margin of clypeus evenly convex. Eyes with 16 ommatidia in a longest row. Scapes relatively short (SI < 85). With head in dorsal view hind margin convex. With mesosoma in profile, dorsal margins of promesonotum and propodeum each convex, with metanotal groove conspicuously impressed. Propodeum hump-shaped in profile, unarmed, with dorsum rounding evenly into declivity. Metapleural lobes low and rounded. Anterior peduncle long and narrow. Subpetiolar process vestigial, visible as a shallow obtuse angle. Petiolar node in profile massive and nodiform with anterior face angled at about 45° whereas posterior face is nearly vertical. Postpetiole low and rounded. Ventral margin of postpetiole in profile obtusely angled, without distinct process. Dorsum of head weakly shining with faint reticulate ground-sculpture; weakly striated between the eyes and more strongly striated between base of antenna and the eyes. Promesonotal dorsum finely reticulate. Propodeal dorsum with irregular reticulate ground sculpture overlaid by faint irregular transverse striations. Base of declivity with strongly developed transverse striations. Petiolar node and postpetiole with irregular sculpture; transverse striations on peduncle and vestigial transverse striations on petiolar node. Base of first gastral tergite with a ring of short costulae; remainder of the tergite predominantly shiny with weak reticulate pattern. Dorsum of head and mesosoma with appressed white, scattered pubescence, no erect hairs. The venter of head with three straight hairs. Propodeum without hairs. Petiolar node and postpetiole each with a pair of backwardly projecting fine long acute hairs in each. First gastral tergite with scattered, short, decumbent hairs, acute apically; with longer erect hairs along the posterior margin and on the sternite. Colour brick red with gaster dark brown.

Paratypes. HL 0.688–0.718, HW 0.531–0.541, HW1 0.565–0.590, CI 75–77, SL 0.462–0.470, SI 87, PW 0.393–0.423, ML 0.859–0.895, EL 0.194–0.207, EI 36–38 (2 of 2 measured). Same data as holotype.

Type Material
Holotype: South Africa: Northern Cape: west of Driefontein farm, Succulent Karoo 2 site (10.7 km 109° ESE Nieuwoudtville), 31°22.581’S 19°13.507’E, 12–19 October 2000, H.G. Robertson, D. Larsen & R. Adams; NW00-SK2P05, SAM-HYM-C019131. Paratype workers with same data as holotype except NW00-SK2-P04, SAM-HYM-C019130, NW00-SK2-Sweep 228, SAM-HYM-C019132.

Etymology
Named after Dawn Larsen, one of the collectors, who is an Assistant Collections Manager in the entomology collection of the Iziko South African Museum.