The Hawaiian bark louse genus Ptycta (Psocoptera: Psocidae) has undergone an extensive species radiation on the Hawaiian Islands. Currently, 51 endemic species of Hawaiian Ptycta are described. Most species are confined to very local distributions on single islands, and several are described from single specimens or small series, indicating that there may be many endemic species yet undescribed. Using new specimens (collected beginning in May 2006) and existing museum specimens, we are investigating the phylogenetic relationships among Hawaiian Ptycta and relatives using morphological characters and sequences from three mitochondrial genes (COI, 12S, and 16S) and the nuclear 18S rDNA gene. The resulting phylogeny will be used to hypothesize a model of the biogeographic history of these species, including the geographic origin of the first colonizers, the number of introductions of Ptycta to Hawaii, and the spatial and temporal patterns of species radiation.