Tetramorium frigidum

Identification
Bolton (1980) - This species shows a greater size-variation than is usual in members of the squaminode-group. For instance, the type-series of the var. drakensbergensis, a straight synonym of T. frigidum, has the range HL 0.66-0.90, HW 0.58-0.86, SL 0.44-0.62. Some minor variations occur between the extremes of this range. The metanotal groove is better defined in larger than in smaller specimens, and also in larger workers the strong cephalic sculpture is more sharply defined. On the other hand, ground-sculpture on the head is fainter in smaller individuals and the incidence of cross-meshes on the sculpture of the alitrunk is distinctly less. Within the squaminode-group T. frigidum is closest related to Tetramorium flaviceps and Tetramorium jejunum, but in both these species the size-range in a given series is by no means as marked as in T. frigidum, the eyes are relatively large (0.26-0.29 x HW) as compared to T. frigidum (0.22-0.24 x HW) and the sculpture of the head is much less regular and nowhere near as sharply defined as in T. frigidum.

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

Nomenclature

 * drakensbergensis. Tetramorium akermani var. drakensbergensis Arnold, 1926: 267 (w.q.) SOUTH AFRICA. Junior synonym of frigidum: Bolton, 1980: 256.
 *  frigidum. Tetramorium akermani var. frigidum Arnold, 1926: 266 (w.) SOUTH AFRICA. Raised to species and senior synonym of drakensbergensis: Bolton, 1980: 256.

Description
Bolton (1980) - TL 2.7-4.0, HL 0.66-0.92, HW 0.58-0.88, CI 89-97, SL 0.44-0.70, SI 71-79, PW 0.42-0.66, AL 0.72-1.10 (20 measured).

Mandibles smooth or with faint longitudinal striation. Anterior clypeal margin with a distinct median notch or impression. Frontal carinae sinuate, strongly developed and reaching back almost to the occipital margin; surmounted by a raised rim or flange which becomes weaker behind the level of the eyes and occipitally has faded out or is no more strongly developed than the remaining cephalic sculpture. Antennal scrobes shallow but broad and conspicuous. Eyes moderately sized, maximum diameter 0.16-0.20, about 0.22-0.24 x HW. With alitrunk in profile the metanotal groove usually shallowly impressed, this being more distinct in larger specimens. Propodeal spines long and strong, the metapleural lobes low and triangular. Petiole squamiform, in profile much higher than long and in dorsal view much broader than long. Postpetiole in profile low and broadly rounded, in dorsal view much broader than long and slightly broader than the petiole. Dorsum of head with sharply defined strong, longitudinal, quite regular rugulae, the spaces between which are only superficially sculptured and glossy. The longitudinal rugulae run from the posterior clypeal margin to the rim of the occipital foramen without cross-meshes and without developing a reticulum occipitally. Dorsal alitrunk predominantly longitudinally rugulose, usually with a few cross-meshes, especially on the anterior pronotum. Petiole, postpetiole and gaster unsculptured. All dorsal surfaces of head and body with numerous short, quite stout hairs, most or all of which are blunted apically. Scapes and tibiae only with fine, short decumbent to appressed pubescence. Colour uniform light brown.

Type Material
Bolton (1980) - Syntype workers, SOUTH AFRICA: Cape Prov., Hex Riv. Mts, Matroosberg 5000-7000 ft [1520-2130 m], 1.1917 (R. W. Tucker) [examined]. Tetramorium akermani var. drakensbergensis. Syntype workers, SOUTH AFRICA: Mts of Natal, 5300 ft [1610 m], iv.1898 (Haviland) (BMNH) [examined].

References based on Global Ant Biodiversity Informatics

 * Addison P., and M. J. Samways. 2000. A survey of ants (Hymenoptera: Formicidae) that forage in vineyards in the Western Cape Province, South Africa
 * Arnold G. 1926. A monograph of the Formicidae of South Africa. Appendix. Annals of the South African Museum. 23: 191-295.
 * 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.
 * Hanrahan S. A., M. J. Steinbauer, and F. D. Duncan. 2014. Ant assemblages in a poorly sampled part of the arid Nama Karoo. African Entomology 22(2): 448453.
 * IZIKO South Africa Museum Collection
 * Parr C., and S. Chown. 2001. Inventory and bioindicator sampling: Testing pitfall and Winkler methods with ants in a South African savanna. Journal of Insect Conservation 5: 27-36.