While ant colonies serve as host to a diverse array of myrmecophiles, few parasitoids are able to exploit this vast resource. A notable exception is the wasp family Eucharitidae, which is the only family of insects known to exclusively parasitize ants. Eucharitidae (Chalcidoidea) contains 54 genera and over 500 described species. Worldwide, eucharitids attack five subfamilies across the ant phylogeny. To evaluate phylogenetic relationships, a molecular dataset was used (18S, 28S-D2, 28S-D3-5, COI, and COII). Eucharitid diversification is examined, including timing of key evolutionary events, biogeographic patterns, and potential cophylogeny with ant hosts. Eucharitidae arose approximately 50 mya after their hosts, during the time when the major ant lineages were already diversifying. Even after multiple dispersal events to the New World and extensive speciation within biogeographic regions, eucharitids remain parasitic on the same ant subfamilies as their Old World relatives, suggesting host conservatism despite access to a diverse novel ant fauna.
A speciose group of eucharitids is the `Kapala clade', which is a group of genera found mainly in the Neotropics. It includes some of the most morphologically bizarre members within the family. Their monophyly is supported in both morphological and molecular analyses. However, relationships among genera within the clade are not so easily resolved. Within this clade, Kapala Cameron is one of the most diverse and easily recognizable genera, with species distributed across the Neotropical region and one disjunct species found in the Afrotropical region. Divergence dating and estimated mutation rates suggest that the age of this species, K. ivorensis, is >1 my, thus predating a human introduction. A morphological matrix of 52 characters was analyzed both separately and combined with molecular data. There was support for the Kapala clade and the described genera sampled, with three major clades being recovered. The genus Kapala was rendered paraphyletic by two distinct clades of other kapaline genera. A redescription is provided for the type species, Kapala furcata, and for Kapala cuprea Cameron 1913. Three new species are described, K. deltalis sp. nov., K. parafurcata sp. nov., and K. quasimodo sp. nov.