Tetramorium sigillum

Identification
Bolton (1980) - Identification: In the flabellum-complex of species, to which sigillum belongs, this is the smallest representative and is quickly separable by the presence of an unsculptured median longitudinal strip on the postpetiole dorsum. This segment is evenly and conspicuously sculptured dorsally in the related species Tetramorium ataxium, Tetramorium flabellum, Tetramorium geminatum and Tetramorium kestrum.

Distribution based on Regional Taxon Lists
Afrotropical Region: Ivory Coast.

Nomenclature

 *  sigillum. Tetramorium sigillum Bolton, 1980: 303, fig. 79 (w.) IVORY COAST.

Worker
Holotype. TL 2.9, HL 0.72, HW 0.62, CI 86, SL 0.58, SI 94, PW 0.45, AL 0.80. Paratypes (20 measured): TL 2.8-3.0, HL 0.68-0.72, HW 0.60-0.63, CI 86-88, SL 0.54-0.60, SI 90-96, PW 0.40-0.50, AL 0.74-0.88. Maximum diameter of eye 0.12-0.13, about 0.19-0.21 x HW.

Mandibles longitudinally striate. Anterior clypeal margin entire, without trace of a median notch or impression. Median clypeal carina strongly developed, the remaining clypeal sculpture consisting ofa few weaker rugulae which arise posterolaterally on the clypeus and run anteriorly, converging on the median carina (not reaching the carina in some paratypes). Frontal carinae strong, running back almost to the occipital margin before merging with the rugose sculpture. Antennal scrobes shallow but conspicuous. Antennal scapes relatively long, SI > 90 in holotype (in paratype series SI 90-96). Maximum diameter of eye 0.12, about 0.19 x HW. Propodeal spines long and strong, very feebly downcurved along their length. Metapleural lobes elongate-triangular. Petiole node roughly rectangular in profile, in dorsal view longer than broad. Dorsum of head strongly longitudinally rugose, with five rugae between the frontal carinae at the level of the eyes. Occipital region with a weakly developed reticulum in which the longitudinal component predominates. Dorsal alitrunk rugose, mainly longitudinal but with a number of cross-meshes. Dorsal surfaces of the main rugae with a beaded appearance due to the presence of aligned minute punctures. Ground sculpture between rugae on head and alitrunk minimal and superficial, the surfaces glossy. Dorsum of petiole finely and quite densely rugulose but the postpetiole dorsum with a broad median longitudinal strip which is without rugular sculpture. In the holotype and most paratypes this strip has very feeble ground-sculpture which is almost effaced, but in a few it is shining. First gastral tergite unsculptured. All dorsal surfaces of head and body with numerous stout hairs which are blunted apically; the hind tibiae with short decumbent to appressed pubescence only. Colour dark brown, the gaster slightly lighter in shade than the alitrunk and head.

Paratypes: As holotype but some specimens blackish brown, the gaster usually lighter brown but sometimes almost as dark as the alitrunk. Propodeal spines vary from approximately straight to feebly sinuate; the majority show a slight downcurvature. On the clypeus 2-4 secondary rugulae converge on the median carina.

Type Material
Holotype worker, Ivory Coast: Tai Forest, 9.viii.1975, no. 5 (T. Diomande). Paratypes. 10 workers with same data as holotype; 12 workers with same locality data but 12.iii.1976, no. 3 (T. Diomande) (BMNH; ; ).

References based on Global Ant Biodiversity Informatics

 * 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.