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Tetramorium severini species group
Based on Bolton, 1979 and Hita Garcia and Fisher 2011, 2014.
This group only holds the species T. severini, which is a common faunal element in most rainforests in eastern Madagascar. Previous to Hita Garcia and Fisher (2011), T. severini was placed in the T. schaufussii group by Bolton (1979). Despite strong similarities in the shape of the mesosoma and waist segments, we still consider T. severini distinct enough from all members of the T. schaufussii group to justify its placement in its own species group. All species of the T. schaufussii group are comparatively small species with very short to moderately long propodeal spines, whereas T. severini is one of the largest species found in Madagascar outside the T. tortuosum, T. kelleri, and T. tosii species groups, and possesses very long propodeal spines. Admittedly few more factors argue for the separation, and future reexaminations may come to a different conclusion. However, at present, we believe the similarities between T. severini and the T. schaufussii group are convergent in nature, an idea also supported by unpublished mtDNA data (FHG & BLF, unpublished data).
Furthermore, the T. severini group can be easily distinguished from all other Malagasy Tetramorium species and groups by its 11-segmented antennae, long and slender mesosoma (LMI 35–37) without distinct margination between lateral and dorsal mesosoma, very long propodeal spines (PSLI 38–43), rounded high nodiform petiolar node, and completely unsculptured waist segments.
Diagnosis
Eleven-segmented antennae; anterior clypeal margin with distinct median impression; frontal carinae strongly developed and long, usually ending shortly before posterior head margin; antennal scrobes present, but weak and without well-developed posterior and ventral margins; anterior face of mesosoma weakly developed; mesosomal outline in profile flat and relatively elongated, only very weakly marginate from lateral to dorsal mesosoma, sides usually rounding onto dorsum; mesosoma relatively low (LMI 35–37); propodeal spines long to very long, spinose and acute (PSLI 38–43); propodeal lobes triangular and short; petiolar node in profile high rounded nodiform, in profile around 1.5 to 1.7 times higher than long (LPeI 57–69), node in dorsal view around 1.1 to 1.2 times wider than long (DPeI 104–121), anterior and posterior faces approximately parallel; postpetiole in profile globular to subglobular; mandibles unsculptured, smooth, and shining; cephalic dorsum with distinct longitudinally rugose sculpture; mesosoma laterally, distinctly, irregularly, and longitudinally rugose to reticulate-rugose, sculpture on mesosomal dorsum relatively weak, usually consisting of feeble, irregular longitudinal rugulae; waist segments and gaster unsculptured, smooth, and shiny; head with numerous standing, long hairs, mesosoma with one or two long hairs, waist segments and first gastral tergite without any standing pilosity; first gastral tergite with very short and appressed pubescence; sting appendage spatulate.
References
- 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.