Tetramorium sikorae Forel 1892

Head much longer than wide (CI 86–89); in full-face view posterior head margin weakly to moderately concave. Anterior clypeal margin with distinct median impression. Frontal carinae moderately developed, slightly diverging posteriorly, becoming weaker halfway between posterior eye margin and posterior head margin, ending at or shortly before posterior head margin. Antennal scrobes weak to absent, shallow and without clear and distinct posterior and ventral margins. Antennal scapes short, not reaching posterior head margin (SI 70–74). Eyes relatively large (OI 26–28). Mesosomal outline in profile flat to weakly convex, comparatively low and long (LMI 36–39), moderately marginate from lateral to dorsal mesosoma; promesonotal suture absent; metanotal groove weak or absent. Propodeal spines reduced to short, triangular, and usually blunt, rarely acute, teeth (PSLI 11–14); propodeal lobes short, triangular, and usually blunt, approximately of same size as propodeal teeth, in profile teeth and lobes not strongly inclined towards each other. Petiolar node in profile high rounded nodiform, around 1.7 to 1.9 times higher than long (LPeI 53–59), anterior and posterior faces approximately parallel, usually anterodorsal and posterodorsal margins situated at about same height and equally rounded, petiolar dorsum weakly to moderately convex; node in dorsal view around 1.2 to 1.3 times wider than long (DPeI 120–133), in dorsal view pronotum between 2.3 to 2.6 times wider than petiolar node (PeNI 38–43). Postpetiole in profile subglobular, around 1.4 to 1.5 times higher than long (LPpI 67–72); in dorsal view around 1.4 to 1.6 times wider than long (DPpI 142–157), pronotum between 1.7 to 2.0 times wider than postpetiole (PpNI 51–58). Postpetiole in profile usually appearing less voluminous than petiolar node, postpetiole in dorsal view around 1.3 to 1.4 times wider than petiolar node (PPI 131–144). Mandibles completely unsculptured, smooth, and shiny; clypeus longitudinally rugulose with three to seven rugulae, median rugula always present and usually fully developed, one or two mostly entire, rarely broken, lateral rugulae present on each side; cephalic dorsum between frontal carinae irregularly longitudinally rugulose with six to ten rugulae, rugulae usually running from posterior clypeal margin to posterior head margin, but mostly irregularly shaped, meandering, interrupted or with cross-meshes; scrobal area mostly unsculptured; lateral head reticulate-rugulose to longitudinally rugulose, posteriorly often partly unsculptured; ground sculpture on head weakly to moderately punctate. Dorsum and sides of mesosoma irregularly longitudinally rugulose to reticulate-rugulose, sometimes in parts only very weakly sculptured and relatively smooth; ground sculpture on mesosoma weak to absent. Forecoxae, both waist segments, and gaster fully unsculptured, smooth, and shining. Dorsum of head with numerous pairs of long, fine, standing hairs; dorsal promesonotum usually with two pairs, rarely three or four; propodeum and waist segments without long, standing pilosity; first gastral tergite with short, moderately dense, appressed pubescence in combination with several scattered, long, standing hairs. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with appressed to decumbent hairs. Head, mesosoma, waist segments and gaster uniformly orange brown contrasting with yellowish to light brown mandibles, antennae, and legs.

Tetramorium sikorae is widely distributed in Madagascar from Andrambovato in Fianarantsoa in the southeast to Binara in the north, and is also found in the isolated montane forest Ambohijanahary in western Madagascar (Fig. 66). Its main distribution is centered in central-eastern Madagascar in the area from Torotorofotsy and Andasibe-Mantadia north to Betampona and Zahamena. Tetramorium sikorae clearly prefers montane rainforests, rarely lowland rainforests, and the elevational range of 240 m to 1100 m must be taken with caution since it is predominantly found at the higher range limit. Also, Tetramorium sikorae seems to be a leaf litter inhabitant.