Francisco Hita Garcia and Brian Fisher have just published an open-access paper on the Tetramorium species groups of Madagascar. Tetramorium is a very large genus and this work, sizeable though it is, really only lays the groundwork for a coming monograph by delineating clusters of similar species and providing a key to the resulting groups.
The paper contains one new species, though: the lovely Tetramorium mahafaly, pictured above.
source: 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.