Tetramorium grassii

A fairly common and widespread species in South Africa, T. grassii has also been introduced into New Zealand, where it appears to be the only established tetramoriine (Brown, 1958; Bolton, 1977).

Identification
Bolton (1980) - Fairly variable as regards propodeal spine length, degree of impression of metanotal groove and density and intensity of sculpture but otherwise consistent in appearance. Within the group T. grassii is closest related to Tetramorium regulare but in the latter species the head has very regular, sharply defined cephalic sculpture and the dorsal pilosity is thicker than in T. grassii and distinctly blunted.

Distribution based on Regional Taxon Lists
Afrotropical Region: Eswatini, South Africa. Australasian Region: New Zealand.

Nomenclature

 *  grassii. Tetramorium grassii Emery, 1895h: 37 (w.) SOUTH AFRICA. Mayr, 1901b: 25 (q.). Senior synonym of algoa, joffrei, laevigatum, mayri, simulans: Bolton, 1980: 262.
 * laevigatum. Tetramorium grassii var. laevigatum Mayr, 1901b: 25 (w.) SOUTH AFRICA. Junior synonym of grassii: Bolton, 1980: 262.
 * joffrei. Tetramorium joffrei Forel, 1914d: 228 (w.q.) SOUTH AFRICA. Junior synonym of grassii: Bolton, 1980: 262.
 * simulans. Tetramorium grassii var. simulans Santschi, 1914e: 24 (w.) SOUTH AFRICA. Junior synonym of grassii: Bolton, 1980: 262.
 * algoa. Tetramorium joffrei var. algoa Arnold, 1917: 304 (w.q.) SOUTH AFRICA. Junior synonym of grassii: Bolton, 1980: 262.
 * mayri. Tetramorium grazsii var. mayri Emery, 1924d: 281 (q.) SOUTH AFRICA. [Unresolved junior secondary homonym of mayri Mann, above.] Junior synonym of grassii: Bolton, 1980: 262.

Worker
Bolton (1980) - Bolton (1980) - TL 3.0-4.1, HL 0.74-0.98, HW 0.66-0.90, CI 88-94, SL 0.59-0.80, SI 79-89, PW 0.48-0.68, AL 0.88-1.12 (40 measured).

Mandibles longitudinally striate, very coarsely so in some samples. Anterior clypeal margin with a median notch or impression which is usually distinct but which may be quite shallow in individuals. Frontal carinae long and sinuate, running back almost to the occipital margin. Frontal carinae surmounted by a raised rim or flange which is conspicuous to the level of the posterior margins of the eyes, behind which it rapidly becomes more feeble. Eyes of moderate size, maximum diameter 0.16-0.22, about 0.24-0.26 x HW. Alitrunk in profile usually with the metanotal groove impressed, but in smaller workers the impression may be feeble or even absent, leaving the dorsum more or less evenly convex. Propodeal spines long, narrow and acute, the length of the spines varying from series to series. Metapleural lobes low and triangular. Petiole in profile a high, narrow node, its thickness varying even in members of the same series but always with the height of the tergal portion greater than the dorsal length. Anterior and posterior faces of the node usually slightly convergent dorsally and the posterodorsal angle more broadly rounded than the anterodorsal. Node of postpetiole in dorsal view high and quite narrowly rounded above. In dorsal view both the petiole and postpetiole broader than long. Dorsum of head sculptured with irregular, broken or wandering longitudinal rugulae, with 7-10 of them present between the frontal carinae at the level of the eyes. In larger specimens the rugulae are more strongly developed than in smaller and in some a few feeble cross-meshes may be present on the dorsum, although an occipital reticulum is never developed. Dorsal alitrunk irregularly rugulose, the rugulae often predominantly longitudinal but many individuals with a loose, open or irregular reticulum. In many populations there is a tendency for the rugulae on the promesonotum to be reduced in density and intensity or even effaced, so that individuals occur in which the alitrunk is mostly or entirely smooth dorsally. In a majority of cases such a reduced sculpture predominates in small workers, but this is by no means unanimous as occasional larger workers can be found in which the alitrunk is almost smooth. Petiole, postpetiole and gaster unsculptured, smooth and shining. All dorsal surfaces of head and body with numerous fine hairs which are acute apically. Scapes and tibiae only with fine decumbent to appressed short pubescence. Colour uniform brown, varying from mid-brown to blackish brown.

Type Material
Bolton (1980) - Syntype workers and female, SOUTH AFRICA: Cape Town (worker) and Kimberley (female) (E. Simon) [worker examined].

References based on Global Ant Biodiversity Informatics

 * Arnold G. 1917. A monograph of the Formicidae of South Africa. Part III. Myrmicinae. Annals of the South African Museum. 14: 271-402.
 * Arnold G. 1960. New species of African Hymenoptera. No. 15. Occasional Papers of the National Museum of Southern Rhodesia. B. Natural Sciences. 3: 452-488.
 * 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.
 * Emery C. 1895. Voyage de M. E. Simon dans l'Afrique australe (janvier-avril 1893). 3e mémoire. Formicides. Annales de la Société Entomologique de France 64: 15-56.
 * Forel A. 1914. Formicides d'Afrique et d'Amérique nouveaux ou peu connus. Bulletin de la Société Vaudoise des Sciences Naturelles 50: 211-288.
 * IZIKO South Africa Museum Collection
 * Koen J. H., and W. Breytenbach. 1988. Ant species richness of fynbos and forest ecosystems in the Southern Cape. South Afr. Tydskr. Dierk. 23(3): 184-188.
 * Santschi F. 1914. Formicides de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri. Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d'Agricoltura. Portici 8: 309-385.
 * Santschi F. 1914. Meddelanden från Göteborgs Musei Zoologiska Afdelning. 3. Fourmis du Natal et du Zoulouland récoltées par le Dr. I. Trägårdh. Göteborgs Kungliga Vetenskaps och Vitterhets Samhälles Handlingar. 15: 1-44.
 * Taylor R. W. 1987. A checklist of the ants of Australia, New Caledonia and New Zealand (Hymenoptera: Formicidae). CSIRO (Commonwealth Scientific and Industrial Research Organization) Division of Entomology Report 41: 1-92.
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004