A detailed study of the moths (Lepidoptera) feeding on most species of shrubs and small trees in the genus Olearia section Divaricaster (family Asteraceae) revealed a particularly rich fauna including eight new species. Furthermore, the plants were found to be complex ecosystems supporting lichens, mosses, and algae, which in turn all support their own moth species. Forty-one species of moth, all endemic to New Zealand, were found to feed naturally on this group of plants. Of these, 20 species were found to be specialists, with 17 species confined to this host group, and the other three species oligophagous within Asteraceae. This Olearia moth guild is divided into 30 herbivores and eleven detritivores. New biological, biogeographical, seasonality, and conservation information is presented in an annotated list of the 20 specialist moth species. The number of moth species on each Olearia species is noted and discussed. The richness of this fauna in different regions is presented. Several of the host plants are threatened with extinction and the conservation of these hosts is supported on entomological grounds.