Tetramorium bicarinatum species group
As defined in Hita Garcia and Fisher. 2011. The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region – introduction, definition of species groups, and revision of the T. bicarinatum, T. obesum, T. sericeiventre and T. tosii species groups. Zootaxa. 3039: 1-72.
12-segmented antennae; anterior clypeal margin with distinct median impression; frontal carinae well-developed, ending shortly before or reaching posterior head margin; anterior face of mesosoma only weakly developed and rounding onto the dorsum; margination between lateral and dorsal mesosoma weak; propodeal spines medium-sized to long and spinose; propodeal lobes triangular to elongate-triangular, acute, and short to medium-sized; petiolar node nodiform, longer than high or as long as high, in two species posterodorsal angle higher situated than anterodorsal; postpetiole roughly rounded; mandibular sculpturation variable; cephalic sculpturation strongly developed, mostly reticulate-rugose, between frontal carinae close to posterior clypeus more rugose, ground sculpturation of head generally faint or absent; mesosoma and waist segments reticulate-rugose; first gastral tergite in some species with basigastral costulae, rest of the gaster unsculptured, smooth, and shiny; all dorsal surfaces with long, erect hairs; sting appendage triangular.
The T. bicarinatum group is represented in the Malagasy region by three species only, all being tramp species with wide distribution ranges. Tetramorium bicarinatum, T. insolens, and T. pacificum are most certainly not native to the Malagasy region and seem to have their native ranges in the Oriental and Indo-Australian regions (Bolton, 1977, 1979; McGlynn, 1999). Tetramorium bicarinatum is the most common of the three and can be found in many localities in Madagascar and its surrounding islands, whereas T. insolens and T. pacificum have not yet reached mainland Madagascar. Tetramorium insolens is only known from Mauritius and Reunion (Blard et al., 2002; Roberts & McGlynn, 2004) while T. pacificum occurs in the Seychelles and Mauritius.
In the Malagasy region, this group cannot be confused with another group with 12-segmented antennae since it is the only one with a medially impressed anterior clypeal margin. Within the species group, the three species can be morphologically well-separated by comparing the shape of the petiolar node, mandibular sculpturation, pilosity, and colouration.