Tetramorium sericeiventre

Bolton, B., 1979, The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Malagasy region and in the New World., Bulletin of the British Museum (Natural History) Entomology 38, pp. 129-181 : 153-155

The sericeiventre -group

Antennae with 12 segments. Mandibles longitudinally striate. Anterior clypeal margin entire, without a median notch or impression. Lateral portions of clypeus modified, appearing roughly dentiform in full-face view (Fig. 34) but with the head viewed from above and slightly behind the raised lateral portions of the clypeus are seen to rise to a distinct high angular peak in front of the antennal insertions and then slope steeply down towards the median portion. Frontal carinae feeble or absent, never extending beyond eyes. Antennal scapes long, SI> 100; antennal scrobes absent. Propodeum bispinose. Petiole in dorsal view longer than broad. Sting appendage triangular to dentiform.

This group is strictly African and contains about a dozen species on that continent, most of which are arid-ground forms feeding largely or exclusively on ants of the genus Pheidole . Two species, in fact the two most common African species, have established themselves in the Malagasy region. In this region sericeiventre is known only from Madagascar, but quadrispinosum is more widely distributed, occurring also on several of the smaller island systems of the region.

Both of these species will be dealt with in more detail in the section of this study dealing with the Ethiopian regional fauna and so only summary treatment is given to them here.

Besides having the species-group characters noted above, both species have a number of stout, blunt hairs arising sparsely on the promesonotum, pedicel segments and gaster, but such hairs are absent from the propodeal dorsum. Both species are reddish in colour, usually with the gaster darker (sometimes black) but sometimes with very little difference in shade between alitrunk and gaster. The antennal scapes and the middle and hind tibiae lack standing hairs of any description and the petiole node in profile is long and low (Fig. 35). Differences between the two species rest rather uneasily upon the variable character of density and intensity of sculpture as tabulated in the key. In reality it is quite possible that quadrispinosum , a feebly or unsculptured form, and sericeiventre , a strongly sculptured form, may represent extremes of a single variable species.

For the present the two forms may be summarized as follows. Tetramorium quadrispinosum Emery Tetramorium quadrispinosum Emery, 1886: 362 , pl. 17, fig. 8. Syntype workers, South Africa: Cape of Good Hope (L. Peringuey) (MRAC, Tervuren; MHN, Geneva) [examined]. Tetramorium blochmanii var. montanum Forel, 1891 a: 152 , pl. 5, fig. 2 a. Syntype workers, Madagascar: nr Tamatave, Bois de l'lvondrona (C. Keller) (MHN, Geneva) [examined]. Syn. n.

Worker. With the group-characters given above and separable from sericeiventre only in terms of sculpture, which in quadrispinosum is feeble. In most specimens the entire dorsum of the head and alitrunk has only weak superficial punctulation or a surface reticulation, but in some a few faint longitudinal rugulae may be developed on the head, the alitrunk, or both. The gaster is often unsculptured but in some may have a superficial reticulation or a narrow band of feeble punctulation close to the base of the first tergite.

This species is widespread in southern Africa and is present in Madagascar. It appears to be fairly common on Aldabra I. and Cosmoledo Atoll.