The Nasutitermitinae is a termite subfamily within the family Termitidae that contains 596 species in 77 genera, distributed globally. The group is characterised by the presence of soldiers with a pointed snout at the front of their heads, known as a nasus, which they use to spray chemicals at predators, as well as highly reduced or absent mandibles. A diverse array of nesting and feeding habits are found among the Nasutitermitinae. They are known to feed on sound and decaying wood, grass, leaf litter, and other decaying vegetable matter, as well as soil. They build their nests under the ground, sometimes under rocks or decaying wood, as well as inside wood, in trees, and as mounds. In Australia, 44 Nasutitermitinae species in six genera have been described. Many of these build mounds, including some of the largest on earth. In this study, I investigated phylogenetic relationships in the Nasutitermitinae, focusing on Australian representatives. I sequenced three mitochondrial genes from a total of 184 specimens, performed phylogenetic and molecular clock analyses to understand the pattern and timing of Nasutitermitinae evolution, and inferred the evolution of nest-building and feeding using ancestral state reconstruction (Chapter 2). The study represents the first detailed molecular investigation of Australian Nasutitermitinae. Previous morphological studies of this group suggested the presence of cryptic species within a number of recognized taxa. I examined species boundaries among Australian Nasutitermitinae samples using the generalised mixed yule coalescent approach, and detected a number of putative species that warrant further investigation (Chapter 3). Based on my results I propose tentative systematic revisions for the group, which require further sampling as well as sequencing and morphological studies for confirmation.