Tetramorium simulator

Arnold's type series was found "preying on termites." A lone non-type specimen (CASENT0250958) provides all the rest of what is know about this ant's biology; collected in Gordonia Duneveld (Northern Cape SA) from a pitfall trap in open shrubland on sandy, parallel dunes 3-8 m above the plains.

Identification
Bolton (1980) - A member of the quadridentatum group. This is a group of 6 species assembled to hold those species with sculptured mandibles and an entire clypeal margin (without median notch or impression) that do not fit into any other group. Other characters which they have in common include frontal carinae which extend back beyond the level of the posterior margins of the eyes, relatively short antennal scapes (SI < 90; range 77-89), a strongly nodiform petiole and a dentiform or pennant-shaped appendage on the apex of the sting.

Tetramorium simulator is one of the most peculiar members of the genus yet found in the region. It is a large, reddish, virtually unsculptured ant which lacks hairs of any description on the dorsal surfaces of the body. It has relatively short appendages, large eyes, deep antennal scrobes and heavy mandibles, and superficially it bears a close resemblance to members of the synonymized genus Decamorium, i.e., Tetramorium decem and Tetramorium uelense.

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

Biology
Hita Garcia and Fisher (2014) - If one considers the whole tribe Tetramoriini, then it becomes apparent that the specialized habitus of Decamorium is not unique. Several authors have stated that Decamorium are specialised termite hunters, and that their specialised morphology could be an adaptation to such a dangerous lifestyle (Arnold 1917; Bolton 1976; Longhurst et al. 1979). Interestingly, both Arnold (1917) in the original description and later Bolton (1980) noted the similarities in general body shape and diet between members of Decamorium and the species Tetramorium simulator from South Africa. We agree that the similarities in morphology are indeed obvious, especially in profile view. However, at present it is not clear whether the shared morphology is based on a close phylogenetic relationship between Decamorium and T. simulator or a result of convergent evolution due to a similar lifestyle hunting termites. We believe the latter more likely since the twelve-segmented antennae, the much broader head, and sculptured clypeus of T. simulator suggest a closer relationship to another group with twelve-segmented antennae than to Decamorium. Therefore, we hypothesise that both have evolved from different Tetramorium lineages and acquired the specialised habitus independently from each other. Another remarkable aspect is the lack of a strong and sharp clypeal shield in T. simulator, which seems to have been reduced in a manner almost similar, though less pronounced, to Decamorium.

Nomenclature

 *  simulator. Tetramorium simulator Arnold, 1917: 297, pl. 7, fig. 102 (w.) ZIMBABWE. See also: Bolton, 1980: 365.

Worker
Bolton (1980) - TL 4.7-5.1, HL 0.94-1.00, HW 0.78-0.86, CI 83-88, SL 0.66-0.74, SI 81-87, PW 0.64-0.72, AL 1.40-1.52 (14 measured).

Mandibles finely, sometimes delicately, longitudinally striate. Anterior clypeal margin entire, without trace of a median notch or impression. Clypeus with a strong median carina running its length, flanked by 2 or more pairs of less strongly developed carinae. Frontal carinae very strongly developed to level of posterior margins of eyes or just beyond, but on the occiput they rapidly fade out or become indistinguishable from the remaining sculpture. From the frontal lobes to approximately the level of the posterior eye margins the frontal carinae have a laterally directed narrow rim or flange which overhangs the scrobes. This rim is strongest anteriorly and narrows posteriorly. Antennal scrobes narrow but deep and conspicuous, forming a strong impression in the sides of the head below the frontal carinae which runs back beyond the level of the eyes. Eyes large, maximum diameter 0.27-0.30, about 0.33-0.36 x HW and with 13-15 ommatidia in the longest row. Propodeal spines in profile short and broad, triangular in shape, but longer than the rounded plate-like metapleural lobes. Node of petiole in profile as in Fig. 141, with the anterior and dorsal faces meeting in a blunt right-angle, the dorsal and posterior faces meeting through a more rounded curve. In dorsal view the node longer than broad. Dorsum of head finely and quite densely longitudinally rugulose, with about 13-15 main rugulae between the frontal carinae at eye level. Occipital region without a rugoreticulum, the longitudinal rugulae continuing to the occipital margin and commonly becoming weaker as they approach it. Ground-sculpture between the rugulae very faint and superficial. Dorsal alitrunk virtually unsculptured, with only faint vestiges of fine longitudinal rugulae, which in some individuals may be fairly numerous. Ground-sculpture vestigial or absent. Petiole and postpetiole dorsally almost unsculptured, often only with very faint fine punctulation but the petiole commonly with some very faint transverse striolae. First gastral tergite unsculptured except for small pits or with an exceedingly fine surface patterning between the pits. Dorsal surfaces of head, alitrunk, petiole, postpetiole and gaster all without hairs of any description; the first gastral tergite with sparse short appressed pubescence. Colour dull red or reddish brown, the gaster darker than the head and alitrunk.

Type Material
Bolton (1980) - Syntype workers, RHODESIA: Malindi, 1.xii.1914 (G. Arnold) [examined].

References based on Global Ant Biodiversity Informatics

 * IZIKO South Africa Museum Collection