Tetramorium squaminode species group

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Based on Bolton 1980[1]

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Diagnosis

Antennae with 12 segments. Sting appendage spatulate, sometimes short and difficult to see. Petiole squamiform, much higher than long in profile and much broader than long in dorsal view. Postpetiole usually rounded-nodiform, only rarely subsquamate or anteroposteriorly compressed. Mandibular sculpture variable, in most species smooth or with only faint traces of sculpture, but in some coarsely striate. Anterior clypeal margin usually indented medially but this is reduced in some species and absent in the repentinum-complex. Frontal carinae strongly developed, reaching back almost to occipital margins.

Antennal scrobes present, broad but quite shallow. Sculpture predominantly absent from pedicel segments so that the petiole and postpetiole are usually smooth. First gastral tergite unsculptured except in umtaliense where short basal costulae occur. Pilosity usually of fairly dense short stout hairs, most or all of which are blunt apically (fine and acute in akermani). Scapes and tibiae equipped with short fine pubescence which is decumbent or appressed, without standing pilosity of any description.

Species complexes

The 13 known species of this group fall into two very unevenly sized complexes of closely related forms. The first of these contains only repentinum and sitefrum, characterized by the position of their eyes, which are shifted well back on the sides of the head, distinctly posterior to the mid length of the sides. Besides this the clypeal notch is lost and there is a tendency for the clypeus to project slightly anteromedially. The sinuous nature of the frontal carinae is suppressed so that they are almost straight and strongly diverge from front to back. The basal margin of the mandible is slightly inflected and the apical and second mandibular teeth are disproportionately large, the third tooth and subsequent denticle-row being very small. Arnold (1926) reports that repentinum feeds on other ants, and it may be the case that the structural modifications shown by these two species are in response to this rather dangerous lifeway.

The second complex, centring on squaminode itself, contains the remaining eleven species of this group. In these the eyes are approximately at the midlength of the sides of the head, the clypeal notch or impression is generally present though reduced in some species, the frontal carinae are markedly sinuate throughout their length and the mandibles are not modified as above.

This complex can be divided roughly into more strongly sculptured forms, in which the mandibles are strongly longitudinally striate (dogieli, platynode, nube, squaminode, umtaliense), and less strongly sculptured forms in which the mandibles are smooth or have only vestiges of sculpture at most (akermani, do, flaviceps, frigidum , jejunum, matopoense).

Most species of the squaminode-group are restricted to southern Africa but sitefrum is found in Ghana, nube in Sudan and squaminode in Tanzania. The enigmatic dogieli is from Kenya but may be misplaced in this group (see under dogieli). All remaining species are confined to Rhodesia and South Africa but this is quite probably a reflection of the distribution of collectors rather than a fact of the distribution of the species.

References