Pheidole is currently the most species rich genus of ants in the world, with many taxa still awaiting description. The phylogenetic relationships of Pheidole are investigated using molecular characters from five gene regions for ~140 species with special interest in understanding factors that may have lead to their remarkable diversity. The results presented here establish a framework for understanding the explosive radiation of this group by providing (1) a phylogenetic estimate and (2) a comparative analysis of life history traits that are likely to have been important in the diversification of the group. In all analyses, Pheidole is recovered as a monophyletic lineage and previous hypotheses of species groups were largely not upheld in the analyses presented here. Workers of the genus Pheidole are dimorphic with a minor and major (soldier) subcaste. A third subcaste of super majors are known in eight species of Pheidole and this trait was found to have arisen multiple times independently throughout the phylogeny. Seed harvesting is common among species of the genus and is thought to be one of the factors leading to the diversification of the group, but additional data will be required to further test this hypothesis. To address biogeographic questions on the origin of the genus, both New and Old World species were included in these analyses, and the results suggest that Pheidole is New World in origin with a possible single introduction into the Old World.