Tetramorium repentinum

Bolton (1980) reported: Arnold (1926) stresses that T.repentinum feeds on other ants, usually on small Pheidole species, and states that the ground around the nest entrances were strewn with the carcasses of other ants.

Identification
Bolton (1980) - Within the squaminode-group the two species T. repentinum and Tetramorium sitefrum form a distinctive complex characterized by the position of their eyes well behind the midlength of the sides of the head and their more or less straight and strongly divergent frontal carinae. Besides this they share a number of other characters such as smooth mandibles, lack of a median clypeal impression (in both there is a tendency for the median area of the clypeus to project slightly), deep antennal scrobes and very regular dense cephalic sculpture. The two species are very closely related and separation rests upon characters of sculpture and pilosity. In T.sitefrum the pilosity is dense and quite long, the hairs of the first tergite being very numerous and longer than the vertical diameter of the eye. Coupled with this the alitrunk in T.sitefrum is very coarsely reticulate-rugose and the dorsum of the postpetiole retains traces of sculpture, whereas this segment is smooth in T.repentinum. Finally the regular longitudinal sculpture of the cephalic dorsum is finer and more closely packed in T.repentinum, coarser and more widely separated in T.sitefrum.

Distribution based on Regional Taxon Lists
Afrotropical Region: Zimbabwe.

Biology
Discovered in 1918, T. repentinum is known from less than ten collections. Two of the three relatively recent collections were pitfall-trap samples from a woodland and a grassland. The third has an excellent account of the collection conditions (from Robertson's specimen notes SAM-HYM-C002576) - a single entrance in sandy soil among short sparse grass. Collected from 10cm below the soil surface. Very close to a Pheidole megacephala nest and many P. megacephala workers in the vicinity. This fits with Arnold's comments on its Pheidole eating habits. The nest entrance was a neat round hole surrounded by a crater of sand. Tetramorium repentinum may get overlooked because it nests so near megacephala nests. Specimens fit Bolton's description very well except the hairs are not blunted apically. Method: saw nest/nest entrance. Habitat: sand on path in coastal bush. Nest: underground.

Nomenclature

 *  repentinum. Tetramorium repentinum Arnold, 1926: 257, fig. 70 (w.) ZIMBABWE. See also: Bolton, 1980: 258.

Worker
Bolton (1980) - TL 3.0-3.4, HL 0.74-0.82, HW 0.72-0.86, CI 97-104, SL 0.50-0.58, SI 67-72, PW 0.50-0.62, AL 0.82-0.90 (10 measured).

Mandibles smooth and shining, the two apical teeth large, much larger than the third. Anterior clypeal margin entire, in most individuals with a small triangular projection medially. Frontal carinae strongly developed, more or less straight, strongly divergent posteriorly and directed towards the occipital corners. Antennal scrobes deep, long and conspicuous, running to the occipital corners behind the eyes. Eyes situated well back on sides of head, distinctly behind the midlength of the sides. Maximum diameter of eyes 0.18—0.22, about 0.25-0.27 x HW. With the head in full-face view the occipital margin shallowly concave, the occipital corners evenly rounded and the sides markedly convergent anteriorly. Alitrunk in profile with the metanotal groove impressed. Propodeal spines stout and strong, the metapleural lobes low and triangular. Petiole strongly squamiform, in profile high and narrow with a very narrow dorsum. Postpetiole in profile lower and much more broadly rounded than the petiole, the sternal portion produced into a freely projecting lobe on each side below the laterally projecting tergite. In dorsal view both nodes very much broader than long, the postpetiole distinctly much more massive than the petiole. Dorsum of head densely and sharply longitudinally rugulose, the rugulae regular, almost straight, and continuous from the anterior clypeal margin to the occiput, without cross-meshes. Posterior margin of clypeus not or only very feebly marked, not interrupting the sculpture. Spaces between the rugulae smooth. Sides of head similarly evenly sculptured. Dorsal alitrunk usually with disorganized fine rugosity. In some individuals an irregular rugoreticulum may be present on the promesonotum but in others the sculpture is finer and predominantly longitudinal, but this sculpture is not as regular or as sharply defined as that on the head. Petiole, postpetiole and gaster unsculptured. All dorsal surfaces of head and body with numerous hairs which tend to be stout and blunted apically. Scapes and tibiae only with appressed minuté pubescence. Colour glossy mid-brown, the gaster usually darker brown.

Type Material
Bolton (1980) - Syntype workers, RHODESIA: Umtali, 9.vi.1920 (G. Arnold); and Umgusa Riv., Sawmills 30.i.1918 (G. Arnold) [examined].

References based on Global Ant Biodiversity Informatics

 * IZIKO South Africa Museum Collection