Taxonomy and Natural History of the Crematogaster (Decacrema)-group (Hymenoptera: Formicidae) in Madagascar

Abstract

The taxonomy of the Malagasy Crematogaster (Decacrema) is revised and a total of six distinct species and one species-complex are recognized. Malagasy Decacrema are widespread ants in Madagascar that nest almost exclusively arboreally, either in carton nests or inside dead twigs or branches, and often tend Coccoidea. Four species are newly described here: Crematogaster mahery sp. nov., C. malala sp. nov., C. sabatra sp. nov. and C. sisa sp. nov.. The species status of Crematogaster grevei Forel 1891 is confirmed by the study, and one described subspecies, C. hova nosibeensis Forel 1891 is raised to species level (C. nosibeensis stat. nov.) and a neotype designated. Crematogaster hova latinoda Forel 1891 is synonymised under C. hova Forel 1887, and the taxonomic status of C. hova, C. ensifera Forel 1910 and C. schencki Forel 1891 is further investigated, but could not be resolved with methods employed here. The C. hova-complex, a species-complex consisting of five morphological forms, is hence defined and the three described species above are associated with these morphotypes. Full descriptions including natural history information are presented for all species and the species-complex, as well as images, distribution maps and a species-identification key to the workers of Malagasy Decacrema. A diagnosis of the Malagasy Decacrema and identification keys to the subgenera of the ant genus Crematogaster in the Malagasy region are also provided.