The native Hawaiian leafhopper genus Nesophrosyne (Cicadellidae: Deltocephalinae) represents a diverse and ubiquitous, yet unstudied element of the Hawaiian entomofauna. Despite initial work, Nesophrosyne is poorly documented both taxonomically and ecologically, and nothing is known about species relationships. The genus is currently comprised of 62 described species. Nesophrosyne is widespread across all high islands of the archipelago (i.e. Kauai – Hawaii), with species occurring in nearly all habitats ranging from coastal scrub to sub-alpine regions. Nesophrosyne species are single island endemics, and are host plant specific. Of the documented host plant associations, Nesophrosyne utilize approximately 25% of the native plant genera, including 75% of the most species rich genera (e.g. lobelloid group, Mrysine, Hedyotis, Coprosma). Preliminary work demonstrates that the many species remain to be described, current subgeneric taxonomic classifications are dubious, and many described species require further taxonomic work utilizing genitalic characters. Phylogenetic analyses provide insight into species relationships, biogeographic patterns and ecological associations. Results show a complex pattern of host plant associations and speciation in Nesophrosyne. Sister taxa on individual islands generally maintain association with a particular host genus and are separated by geographic barriers. Widespread host plant species across all high islands offer a route for island colonization and speciation in the genus. Host genus switching is common in Nesophrosyne, generally occurring between islands. Fine scale investigation of species associated with the widespread host plant Broussaisia arguta illustrates that taxonomically cryptic sister species may be common, and that they are endemic to single volcanoes or discrete geographic ranges.