Tetramorium rufescens

A common, ground nesting species found in a range of open habitats, e.g., rocky slopes, shrubland, desert, floodplain, highly disturbed areas, and sites with little or no vegetation.

Identification
Mbanyana et al. (2018) - The description of this species matches that of Bolton (1980), except for colour. We observed some variation in the specimens examined, ranging from red to light brown, in those collected at certain localities in South Africa (Klein Pella) and Namibia (Kamanjab, Luderitz District, Daberas, Hobatere, Epupa Falls).

The following character combination distinguishes T. rufescens from Tetramorium glabratum and Tetramorium signatum: dorsum of mesosoma with dense reticulate punctate sculpture and propodeal spines long and narrow (PSLI 16–23).

Distribution
Tetramorium rufescens has been recorded from South Africa (Western Cape, Northern Cape, Gauteng, Eastern Cape and KwaZulu Natal); and Namibia.

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

Habitat
Known from Drakensberg Montane Grasslands, Kalahari Xeric Savanna, Nama Karoo, the Namib Desert, Namibian Savanna Woodlands, and Succulent Karoo.

Biology
Robertson encountered T. rufescens numerous times. A few of these collections include these informative field notes:

SAM-HYM-C001039 - Nest entrance next to stone bound by half crater of sand on the one side and the stone on the other. Extensive seed stores in 1st 10cm of soil. Tried to dig down to central portion of colony but hit solid rock. Origin: ground nest, in soil next to rock, with entrance in open at base of rock. Food: seeds.

SAM-HYM-C001044 - Origin: ground nest. Method: saw hole/nest entrance. Habitat: flooplain, acacia.

SAM-HYM-C009186 – Foragers, open savanna on red clay soils with pointed termite mounds

Hawkes (2020) - A 2019 field study sampled 390 T. rufescens in 40 pitfall traps (from 10 transects of 20 traps 10m apart and run for 6 days). Transects were placed in the major habitat types (riverine fringe, alluvial terrace gravels, alluvial fans, aeolian sands, Mispah soils and mountain slopes) of a diamond mine concession in northern Richtersveld National Park (Namakwa district, Northern Cape, South Africa). Tetramorium rufescens was found in five of the six habitats.

Nomenclature

 *  rufescens. Tetramorium solidum st. rufescens Stitz, 1923: 163 (w.) NAMIBIA. Raised to species: Bolton, 1980: 249.

Worker
Bolton (1980) - TL 4.0—5.1, HL 1.04-1.28, HW 0.92-1.18, CI 88-95, SL 0.78—0.88, SI 71-80, PW 0.62-0.80, AL 1.04-1.34 (12 measured).

Mandibles longitudinally rugose. Antennal clypeal margin with a small, narrow median notch or impression which may be difficult to see when the mandibles are fully closed. Frontal carinae extending back to a point about level with the anterior margins of the eyes by a weak ridge which is, however, usually more strongly developed than the remaining cephalic sculpture. Approximate points of termination of the frontal carinae marked by an erect hair on each side of the head. Antennal scrobes absent. Maximum diameter of eye 0:27-0:32, about 0-25-0-28 x HW. Propodeal spines long, narrow and acute, much longer than their basal width. Metapleural lobes low and rounded. Petiole in profile strongly nodiform, in dorsal view slightly broader than long and much broader behind than in front; anterior face of node quite narrowly rounded and the sides diverging strongly posteriorly. Postpetiole in dorsal view distinctly broader than long, with rounded sides, much broader than the petiole. Dorsum of head finely and quite densely longitudinally costulate or rugulose, the spaces between them with only faint, superficial ground-sculpture; glossy in large individuals. Dorsal alitrunk finely and densely reticulate-punctate, commonly with a few weak longitudinal costulae or rugulae on the promesonotum. Dorsal surfaces of petiole and postpetiole very weakly but densely reticulate-punctulate, in some this sculpture very feeble so that the surface appears merely roughened or lightly shagreened. Base of first gastral tergite lightly shagreened. Erect hairs absent from dorsal surfaces of alitrunk, pedicel segments and first gastral tergite; present on clypeus, first gastral sternite and segments behind the first. Dorsum of head with two pairs of hairs, one at the apices of the frontal carinae, the other on the occipital corners. Ventral surface of head with psammophore. Hind tibiae with appressed pubescence. Colour dull red, usually with the gaster darker in shade than the alitrunk and head.

Mbanyana et al. (2018) - (N = 13) HL 0.983–1.200 (1.065); HW 0.954–1.151 (1.021); SL 0.708–0.856 (0.772); EL 0.266–0.325 (0.291); PH 0.393–0.570 (0.460); PW 0.610–0.777 (0.678); WL 1.003–1.141 (1.101); PSL 0.167–0.236 (0.206); PTH 0.315–0.403 (0.348); PTL 0.275–0.325 (0.305); PTW 0.295–0.425 (0.343); PPH 0.315–0.418 (0.362); PPL 0.226–0.291 (0.259); PPW 0.369–0.521 (0.433); OI 27–30 (29); CI 91–100 (96); SI 73–81 (76); DMI 57–69 (62); LMI 36–50 (42); PSLI 16–23 (19); PeNI 46–61 (50); LPeI 78–100 (88) DPeI 97–127 (112); PpNI 59–75 (64); LPpI 59–77 (72); DPpI 154–188 (167); PPI 121–133 (127).

Type Material
Mbanyana et al. (2018) - Syntypes. Namibia: 3 pinned workers, Swakopmund, 12–19 Apr. 1911, W. Michaelsen leg. (: FOCOL2082 to FOCOL2084).

References based on Global Ant Biodiversity Informatics

 * Bolton B. 1980. The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History). Entomology 40: 193-384.
 * IZIKO South Africa Museum Collection
 * Koch F., and K. Vohland. 2004. Ants along a southern African transect - a basis for biodiversity change monitoring (Insecta, Hymenoptera, Formicidae). Zoosystematics and Evolution 80(2): 261-273.
 * Marsh A. C. 1985. Forager abundance and dietary relationships in a Namib Desert ant community. S. Afr. J. Zool. 20: 197-203.
 * Marsh A. C. 1986. Ant species richness along a climatic gradient in the Namib Desert. Journal of Arid Environments 11: 235-241.
 * Marsh A. C. 1986. Checklist, biological notes and distribution of ants in the central Namib Desert. Madoqua 14: 333-344.
 * Mbanyana N. 2013. Taxonomy, phylogeny and biogeography of seed-harvesting ants in the Tetramorium solidum-group (Hymenoptera: Formicidae). Masters of Science in the Department of Botany and Zoology at Stellenbosch University 115 pages.
 * Mbanyana N., F. Hita Garcia, H. G. Robertson, and J. J. Le Roux. 2018. A taxonomic revision of seed harvester ants of the Tetramorium solidum group (Hymenoptera: Formicidae) in southern Africa. European Journal of Taxonomy 454: 1-59.
 * Robertson H. G. 2000. Formicidae (Hymenoptera: Vespoidea). Cimbebasia Memoir 9: 371-382.