This dissertation focuses on the systematics of the Paussinae, a lineage of approximately 775 beetle species all of which produce explosive defensive chemicals and many which are obligate associates of ants (myrmecophiles). This dissertation includes six discrete studies, which taken together span the spectrum of systematic research. It includes taxonomic projects on both larval and adult paussines. It also includes phylogenetic investigations, based on DNA sequence data and morphological data, that address the evolutionary relationships among the major lineages within Paussinae as well as the evolutionary position of the Paussinae within the beetle suborder Adephaga. The inferred trees are used to study character evolution of physiological and behavioral traits of these organisms in a phylogenetic framework. This work sets the stage for a lifetime of work on this fascinating group.