Tetramorium signatum

This species nests in sandy to loamy soils, entrances sometimes with crater of soil around them. Alates were collected from nests in December. Two nests were found with Thysanura inquilines. This species has been collected by digging up nests and also from pitfall traps, yellow pan traps, tuna baits, sugar baits and cookie baits. (Mbanyana et al. 2018)

Identification
Mbanyana et al. (2018) - Tetramorium signatum is similar to Tetramorium rufescens and Tetramorium pogonion. Tetramorium pogonion is relatively smaller compared to the other two species with relatively larger eyes (OI > 30) and a different head shape. Tetramorium signatum and T. rufescens can be separated on basis of the sculpture pattern on the dorsum of mesosoma. In T. signatum, the dorsum of the mesosoma has distinct longitudinal or irregular rugulae, whereas in T. rufescens, the dorsum of the mesosoma has a dense reticulate punctation and sometimes with a few short faint longitudinal costulae.

Distribution
This species has been recorded from South Africa (Eastern Cape, Western Cape, and Northern Cape), Namibia and Angola.

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Namibia, South Africa. Palaearctic Region: Israel.

Habitat
Known from the following ecoregions: Albany Thickets, Kalahari Xeric Savanna, Kaokoveld Desert, Knysna-Amatole Montane Forests, Montane Fynbos and Renosterveld, Nama Karoo (including Koedoesberge-Moordenaars Karoo), Namib Desert, Namibian Savanna Woodlands and Succulent Karoo.

Nomenclature

 *  signatum. Tetramorium solidum var. signatum Emery, 1895h: 35 (w.) SOUTH AFRICA. Raised to species and senior synonym of grootensis, lugubre, tuckeri: Bolton, 1980: 251.
 * lugubre. Tetramorium solidum subsp. lugubre Forel, 1910e: 425 (w.) ANGOLA. Junior synonym of signatum: Bolton, 1980: 251.
 * grootensis. Tetramorium solidum var. grootensis Forel, 1913a: 118 (q.m.) SOUTH AFRICA. Junior synonym of signatum: Bolton, 1980: 251.
 * tuckeri. Tetramorium solidum var. tuckeri Arnold, 1926: 259 (w.q.) SOUTH AFRICA. Subspecies of solidum: Prins, 1973: 5. Junior synonym of signatum: Bolton, 1980: 251.

Mbanyana et al. (2018) - The material examined matched mostly Bolton’s description, but a number of differences were noted. Interestingly, the colour variation in this species is explained by geographical distribution. It looks like there are two forms, the Karoo form and the Kalahari sand form. The specimens collected in the Karoo region mainly in South Africa are brown to black. The specimens collected from red sand dunes (Northern Cape, i.e., Dreghorn and Cullinan Farm, and parts of southern Namibia) are reddish. There is also variation in sculpture pattern. In black coloured specimens, the mesosoma has a strong irregular sculpture on the pronotum and short longitudinal striations on the mesonotum with a punctulate sculpture in between. The nodes have a punctulate sculpture overlain by irregular striations. The first gastral tergite is punctulate or shagreened at the base. Most of the reddish specimens have a strong, irregular sculpture on the pronotum and short longitudinal striations on the mesonotum with a punctulate sculpture in between. In a few specimens, the nodes are predominantly smooth with only reticulate sculpture. The spine length varies in all forms from medium, which are broad at the base, to very short. Based on that high degree of morphological variation, there is a possibility that there is more than one species within both T. signatum and T. rufescens.

Worker
Mbanyana et al. (2018) - (N = 47) HL 0.885–1.249 (1.092); HW 0.875–1.219 (1.053); SL 0.708–0.934 (0.808); EL 0.266–0.344 (0.308); PH 0.393–0.590 (0.488); PW 0.570–0.816 (0.695); WL 0.944–1.328 (1.139); PSL 0.079–0.246 (0.179); PTH 0.285–0.438 (0.348); PTL 0.246–0.384 (0.319); PTW 0.275–0.471 (0.356); PPH 0.295–0.482 (0.377); PPL 0.226–0.334 (0.279); PPW 0.315–0.610 (0.437); OI 25–33 (29); CI 90–105 (96); SI 71–82 (77); DMI 55–81 (61); LMI 35–57 (43); PSLI 7–21 (16); PeNI 45–58 (51); LPeI 80–108 (92); DPeI 93–124 (112); PpNI 51–75 (63); LPpI 62–97 (74); DPpI 128–200 (157); PPI 106–132 (123).

Type Material
Mbanyana et al. (2018):

South Africa: syntype of Tetramorium solidum var. signatum Emery, 1895: 1 pinned worker, Western Cape, Matjiesfontein, E. Simon leg. (: CASENT0904841); syntypes of Tetramorium solidum var. grootensis Forel, 1913: 1 pinned queen, 1 pinned male, Eastern Cape, Willowmore, H. Brauns leg. (: CASENT0901188; : CASENT0909156).

Angola: syntype of Tetramorium solidum subsp. lugrubre Forel, 1910: 1 pinned worker, Mossamedes, de Picard leg. (MHNG: CASENT0909157).

Namibia: syntypes of Tetramorium solidum var. tuckeri Arnold, 1926: 1 pinned queen, 1 pinned worker, Brehdon, 20 Dec. 1915, R.W.E. Tucker leg. (BMNH: CASENT0901189; : SAM-ENT-0011762).