Tetramorium marginatum species group


 * Tetramorium hector
 * Tetramorium marginatum
 * Tetramorium norvigi
 * Tetramorium shamshir
 * Tetramorium silvicola
 * Tetramorium valky

Based on Hita Garcia and Fisher 2012.

Key to Tetramorium marginatum-group species

Tetramorium species groups

Endemic to the island of Madagascar. All species live in humid forest habitats, such as tropical rainforests, littoral rainforests, and montane rainforests.

All members of the group are fairly conspicuous and easily distinguishable from all the other Malagasy Tetramorium with 11-segmented antennae. The very strong reduction of sculpture on head, mesosoma, and waist segments, the generally well-developed margination from lateral to dorsal mesosoma, and the generally triangular or cuneiform petiolar node distinguish this group from others in the region.

The group can be further divided into the four species with a completely unsculptured mesosoma and very dark brown to blackish colouration, T. valky, T. hector, T. marginatum, and T. silvicola, and the two species, T. norvigi and T. shamshir, which are of yellowish to pale brownish colour and display a dorsally rugulose mesosoma

Diagnosis
Eleven-segmented antennae; anterior clypeal margin medially impressed; frontal carinae well developed but generally of moderate length, usually ending approximately halfway between posterior eye margin and posterior head margin; anterior face of mesosoma not well developed and no distinct anterodorsal margin present; mesosoma moderately to strongly marginate, dorsum usually sharply separated from lateral mesosoma; mesosoma comparatively high (LMI 37 - 45); propodeal spines long to extremely long, and spinose; propodeal lobes triangular and short; petiolar node in profile generally triangular cuneiform or thickly cuneiform, usually strongly anteroposteriorly compressed dorsally, in profile much higher than long, anterior and posterior faces not parallel, often anterodorsal angle much better developed and situated higher than posterodorsal angle, dorsum then tapering backwards posteriorly, in dorsal view distinctly wider than long and transverse; postpetiole approximately rounded and weakly anteroposteriorly compressed; mandibular sculpture variable, but often reduced; cephalic sculpture to a large extent reduced and absent; mesosoma in most species completely unsculptured, in two species weak irregular longitudinal rugulae present; waist segments and gaster unsculptured, smooth, and shiny; all dorsal surfaces of head, mesosoma, waist segments and first gastral tergite with few to relatively abundant, whitish, long, fine standing hairs; never with short, dense, and appressed pilosity or pubescence; sting appendage spatulate.