Tetramorium bicarinatum species group
Based on: Hita-Garcia and Fisher 2011 and Agavekar et al. 2017.
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.
Agavekar et al. (2017) - Twelve-segmented antennae; anterior clypeal margin notched and unspecialized; eyes moderately sized to large; antennal scapes short to moderately long, not surpassing posterior head margin; antennal scrobes usually present, but shallow and not clearly defined posteriorly and ventrally; frontal carinae always strongly developed and reaching posterior head level; base of first gastral tergite not concave in dorsal view, without tubercles or teeth on each side; pilosity on dorsal surfaces of body erect with long and fine hairs; sting appendage dentiform.
The T. bicarinatum group is represented in the Malagasy region by three species only, all being tramp species with wide distribution ranges. Tetramorium bicarinatum, Tetramorium insolens, and Tetramorium 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.
This is a relatively species-rich group with 16 species in the Indomalayan and Australasian regions and nine in the Afrotropical region. At present, the group is represented in India by five species, of which two are global tramps. It is challenging to ascertain if these ants are native members of the Indian myrmecofauna or introduced. The taxonomy of the group on the whole is complicated and identifications with the currently available resources are often challenging. In parts this is also true for the Indian species. The species delimitations of Tetramorium indicum, Tetramorium pacificum, and Tetramorium scabrum are not clear and misidentifications can occur easily. The identity of Tetramorium petiolatum is even more doubtful. Its original description is of comparatively poor quality and the authors state that the species is close to T. pacificum (Sheela & Narendran, 1998). However, based on their line drawings it looks very much like Tetramorium bicarinatum and Tetramorium indicum. Since the type material is not available for examination the true identity of this species will remain obscure.
- Gaurav Agavekar, G., Hita Garcia, F., Economo, E.P. 2017. Taxonomic overview of the hyperdiverse ant genus Tetramorium Mayr (Hymenoptera, Formicidae) in India with descriptions and X-ray microtomography of two new species from the Andaman Islands. PeerJ 5:e3800 (DOI 10.7717/peerj.3800).
- Hita Garcia, F.; Fisher, B. L. 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.