Tetramorium avium

The relatively small number of collections of this species were made in a range of habitats from grassland to forest.

Identification
This species and Tetramorium frenchi form a close species-pair within the setigerum-complex of this group. The two are best separated on the structure of the petiole which in T. avium conspicuously narrows from base to apex in profile, and has both the antero- and posterodorsal angles rounded. In T. frenchi on the other hand the node is scarcely or not narrowed from base to apex and the angles are sharply defined, especially the anterodorsal which is a sharp right-angle, often projecting as a low crest or peak. Beside this T. frenchi has a narrow band of punctulation or shagreening on the base of the first gastral tergite, although it may be faint in some individuals, and also has the alitrunk sculpture stronger, with distinct, quite coarse rugulae on the pronotum. Tetramorium avium is the host-species of the inquiline Tetramorium parasiticum, described below from a single female found in a nest of T. avium. A comparison of the female of T. avium with this parasitic species is given under T. parasiticum.

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

Nomenclature

 *  avium. Tetramorium avium Bolton, 1980: 276, figs. 58, 63, 64 (w.q.) SOUTH AFRICA.

Worker
Holotype. TL 3.4, HL 0.75, HW 0.64, CI 85, SL 0.70, SI 109, PW 0.49, AL 0.95. Paratypes (29 measured): TL 3.1—3.7, HL 0.70-0.78, HW 0.60-0.67, CI 82-86, SL 0.64-0.70, SI 103-109, PW 0.44-0.50, AL 0.82-0.96 Maximum diameter of eye 0.16-0.18, about 0.25-0.28 x HW.

Mandibles longitudinally striate. Anterior clypeal margin entire, without a median notch or impression. Frontal carinae long, reaching back almost to the occipital margin and surmounted by a low rim or crest so that the carinae are more strongly developed than the remaining cephalic sculpture. Maximum separation of carinae about 0.50 x HW. Antennal scrobes vestigial, very shallow. Antennal scapes relatively long, SI > 100. Maximum diameter of eye 0.18, about 0.28 x HW. Alitrunk in profile with the metanotal groove feebly impressed. Propodeal spines relatively short, acute apically, longer than the metapleural lobes but shorter than the maximum diameter of the eye. Metapleural lobes triangular. Petiole in profile with a long anterior peduncle and a high, quite narrow node, the dorsal length of which is distinctly less than the height of the tergal portion. Anterior and posterior faces of the node in profile distinctly convergent dorsally, both the antero- and posterodorsal angles blunt, the latter more broadly rounded than the former. Petiole in dorsal view distinctly broader than long. Dorsum of head irregularly longitudinally rugulose, without a rugoreticulum occipitally although one or two weak cross-meshes or anastomoses are present. Groundsculpture of head granulate or finely punctulate, weakly developed. Dorsal alitrunk finely reticulatepunctulate, the pronotum with a few feeble, superimposed irregular rugulae which tend to fade out on the mesonotum but which are again visible in the vicinity of the metanotal groove. Dorsal petiole and postpetiole predominantly finely reticulate-punctulate but with a few very weak fine rugulae. Base of first gastral tergite smooth and highly polished. All dorsal surfaces of head and body with numerous strong, standing hairs. Antennal scapes and tibiae of middle and hind legs with short, fine, decumbent to appressed pubescence only. Colour mid-brown, the gaster slightly darker in shade than the head or alitrunk.

Paratypes: Variation in the paratypes is predominantly in colour, which varies from mid-brown to blackish brown, and in the propodeal spine length. In most material the spines are as in the holotype but in some workers they are smaller, only about the same length as the metapleural lobes or even slightly shorter. (In one non-paratypic series the spines are reduced to teeth which are distinctly shorter than the metapleural lobes.) As the cephalic rugulae between the frontal carinae are irregular and usually broken or interrupted it is difficult to assess the number of them, but there are generally 7-10 at the level of the midlength of the eyes.

Type Material
Holotype worker, South Africa: Cape Prov., Seaview, Port Elisabeth, 2.iii.1969, hillscrub, no. M325 (W. L. Brown). Paratypes. South Africa: 14 workers with same data as holotype; 14 workers and | female, Cape Prov., Grahamstown, Fern Kloof, 19.ii.1969, no. M87, rotten wood, damp kloof (W. L. Brown); 1 worker, Grahamstown, iv.1915 (J. Hewitt). (MCZ; ; ; )

References based on Global Ant Biodiversity Informatics

 * Kotze D. J., and M. J. Samways. 2001. No general edge effects for invertebrates at Afromontane forest/grassland ecotones. Biodiversity and Conservation 10: 443466.
 * Kotze D. J., and M. J. Samways. Invertebrate conservation at the interface between the grassland matrix and natural Afromontane forest fragments. 1999. Biodiversity and Conservation 8: 1339-1363.