Nesomyrmex karooensis

Collected in pitfall and yellow pan traps. Recorded mainly from Nama-Karoo but also collected from Renosterveld on tillite.

Identification
Mbanyana and Robertson (2008) - A member of the simoni species-group. Nesomyrmex karooensis can be distinguished from other members of the genus by the petiolar node, which in profile has angulate anterodorsal and posterodorsal angles. In other species, the petiolar node in profile has a rounded posterodorsal angle and the anterodorsal angle is either angulate or rounded.

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

Nomenclature

 *  karooensis. Nesomyrmex karooensis Mbanyana & Robertson, 2008: 47, figs. 4d-f (w.) SOUTH AFRICA.

Worker
Holotype. HL 0.684, HW 0.531, HW1 0.605, CI 78, SL 0.482, SI 91, PW 0.384, ML 0.821, EL 0.246, EI 46.

Mandibles predominantly smooth with fine striations basally. Median clypeus smooth and shining and bordered by 2 pairs of longitudinal striations. Anterior clypeal margin in dorsal view more or less evenly convex except flattened medially. Scapes relatively long, (SI 91). Large eyes, with 14 ommatidia in a longest row. With the head in full-face view hind margin feebly convex. Promesonotum in profile evenly convex dorsally; and with metanotal groove conspicuously impressed. Dorsum of propodeum shallowly convex and sloping evenly into the declivity, which is about 20 degrees less than vertical. Propodeum armed with a pair of triangular teeth, with basal width broader than the length. Metapleural lobes low and rounded. Anterior peduncle short, with well-developed rounded-triangular subpetiolar process. Posterior face of petiolar node slightly more steeply angled than anterior face and rounding evenly into dorsum; anterior face also rounding into dorsum but angled at the interface between the two. Dorsum in profile short, slightly convex. Postpetiole low and rounded in lateral view. Dorsum of head smooth and shining medially, with short longitudinal rugulae and irregular rugulae near the inner margin of the eyes. Promesonotal dorsum smooth centrally, with reticulate sculpture posteriorly, and with irregular transverse striations anteriorly. Propodeal dorsum and declivity with transverse striations. Base of first gastral tergite with short costulae and the rest of tergite predominantly smooth. Dorsal surface of head, promesonotum, propodeum and nodes with scattered fine short erect hairs. The venter of head with four curved hairs and five suberect hairs; pubescence present. Regularly spaced subdecumbent hairs on tergite and sternite of the gaster. Colour uniformly yellow-brown.

Paratypes. HL 0.689–0.875, HW 0.549–0.683, HW1 0.598–0.731, CI 77–80, SL 0.492–0.634, SI 89–93, PW 0.386–0.500, ML 0.747–1.039, EL 0.209–0.261, EI 38–44 (6 of 18 measured).

Same as holotype with the following differences: mandibles smooth and shining, with hair pits. In dorsal view anterior clypeal margin convex but almost flattened anteriorly, with a projecting translucent lamella medially. Anterior peduncle short, with a small tooth-like or keel-like subpetiolar process. Promesonotal dorsum smooth medially, surrounded by irregular reticulate sculpture and a few irregular rugulae. Propodeal dorsum either with predominantly transverse striations or reticulate-punctate. Petiolar node with irregular striations dorsally, or with irregular reticulate pattern, which is more sharply defined beyond the nodal areas. Postpetiole with irregular rugulae. Base of first gastral tergite with short costulae and the rest of the tergite smooth and shining. Head with short erect hairs at the back of the head and 2 longitudinal lines of erect hairs running between the eyes. The venter of head with 1–4 curved hairs and at least two suberect hairs; sparse pubescence present. Promesonotum with 5–6 pairs of erect hairs, acute apically, propodeum with 1–2 pairs of erect hairs, petiolar node with 2–3 pairs of erect hairs and postpetiole with at least four pairs of erect hairs. Colour light brown to yellow-brown.

Type Material
Holotype: South Africa: Western Cape: Kamferskraal farm, 32°13.61’S 22°58.43’E, 22–29 April 2001, H.G. Robertson & R. Tourle, BW01-K2-P05, SAM-HYM-C019114. Paratypes: South Africa: Western Cape: Avondale farm, 32°15.00’S 22°56.60’E, 22–29 April 2001, S. van Noort & D. Larsen, BW01-A1-Y91, SAM-HYM-C019115; Elandsfontein farm, 32°18.50’S 22°55.04’E, 22–29 April 2001, H.G. Robertson; BW01-D1-P08, SAM-HYM-C019113; Northern Cape: Hopetown, 4 km E of Hopetown, Hopetown Municipal farm; 29°38’0”S 24°9’0”E; 15 February 1997, B. Chambers, SAM-HYM-C010848; Papkuilsfontein farm, Matjie Site (16.7 km 176°S Nieuwoudtville), 31°30.915’S 19°10.960’E, 12–19 October 2000, S. van Noort & H.G. Robertson, NW00-TN3-Y87, SAM-HYM-C019124; Glen Lyon farm, Sheep’s Leg (4.62 km 153° SSE Nieuwoudtville), 31°24.359’S 19°08.895’E, NW00-TN2-P10, 11–18 October 2000, H.G. Robertson, D. Larsen & R. Adams, SAM-HYMC019126; Papkuilsfontein farm, Ostrich Site (16.5 km 177°S Nieuwoudtville), 31°30.808’S 19°10.873’E, 12–19 October 2000, H.G. Robertson, D. Larsen & R. Adams, NW00-TN4P06, SAM-HYM-C019129.

Etymology
So named because most of the specimens were collected in the Karoo, the extensive semi-arid region in southern Africa.

References based on Global Ant Biodiversity Informatics

 * 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.
 * Mbanyana N., and H. G. Robertson. 2008. Review of the ant genus Nesomyrmex (Hymenoptera: Formicidae: Myrmicinae) in southern Africa. African Natural History 4: 35-55.