Tetramorium nigrum

Found in a range of closed to semi-open habitats that include hardwood forest, bushveld, and miombo woodland. One collection was from shrubs and vegetation in a coastal area.  Tetramorium nigrum have been found in a rotten log, litter and pitfall samples, and at a honey bait.

Identification
A member of the Tetramorium simillimum species group.

Bolton (1980) - This minute species resembles a small version of Tetramorium altivagans but is separated from it by lacking developed propodeal teeth and by having shorter antennal scapes (SI 84-91 in T. altivagans). Despite this I am not really sure that the differentiation is justified as a short series from Botswana, Okavango, collected by A. Russell-Smith matches T. nigrum (as represented by T. brevis holotype) in many respects but is intermediate in size between that species and T. altivagans and originates a great distance away from the localities noted above.

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

Nomenclature

 *  nigrum. Tetramorium pauper subsp. nigrum Forel, 1907a: 15 (w.) KENYA. Raised to species and senior synonym of brevis: Bolton, 1980: 316.
 * brevis. Tetramorium brevis Weber, 1943c: 370 (w.) SUDAN. Junior synonym of nigrum: Bolton, 1980: 316.

Bolton (1980) - The problem of how many species are represented here is unable to be solved at present and will have to await the amassing of more material in this complex from all over eastern and southern Africa. Despite this confusion I feel fairly certain of the synonymy of T. nigrum with T. brevis as Weber’s holotype matches Forel’s original description of T. nigrum very well.

Worker
Bolton (1980) - TL 1.9, HL 0.52, HW 0.44, CI 85, SL 0.34, SI. 77, PW 0.30, AL 0.55.

Mandibles mostly smooth but with delicate traces of striation. Anterior clypeal margin without a median notch, regularly arcuate. Frontal carinae feeble but extending back beyond the eyes, posteriorly no more strongly developed than the remaining cephalic sculpture. Antennal scrobes vestigial. Eyes of moderate size, maximum diameter 0.11, about 0.25 x HW and with 7 ommatidia in the longest row. Propodeum in profile sharply descending posteriorly, the dorsum and declivity separated only by an angle or a pair of minute tubercles, without triangular teeth. Petiole node in dorsal view broader than long. Dorsum of head irregularly and finely longitudinally rugulose, the ground-sculpture a fine superficial punctulation or shagreening. Dorsal alitrunk with a similar ground-sculpture to that of head, overlaid by numerous fine, short longitudinal rugulae. Petiole and post-petiole finely punctulate and with vestigial traces of rugular sculpture. First gastral tergite smooth and shining. All dorsal surfaces of head and body with scattered short, stout, blunt hairs. Colour dark brown, the appendages yellow-brown.

Type Material
Bolton (1980) - Holotype worker, KENYA: Mto-ya-Kifaru (Katona) (type not found). Holotype worker, SUDAN: Imatong Mts, W. slopes, 2.viii.1939, 5600 ft [1710 m], no. 1405 (N. A. Weber) [examined].

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.
 * 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
 * Weber N. A. 1943. The ants of the Imatong Mountains, Anglo-Egyptian Sudan. Bulletin of the Museum of Comparative Zoology 93: 263-389.