This paper provides new taxonomic and biological data on a complex of gracillariid moths in the endemic genus Philodoria Walsingham, 1907 that are associated with Myrsine (Primulaceae) in the Hawaiian Islands, United States. Two new species, Philodoria kauaulaensis Kobayashi, Johns & Kawahara, sp. n. (host: Myrsine lanaiensis, M. lessertiana, and M. sandwicensis) and P. kolea Kobayashi, Johns & Kawahara, sp. n. (host: M. lessertiana) are described. Biological data are provided for two previously described species that also feed on Myrsine: P. auromagnifica Walsingham, 1907 and P. succedanea Walsingham, 1907. For the first time we detail and illustrate genital structures, immature stages, biology, and host plants of P. auromagnifica and P. succedanea. Philodoria kolea, P. auromagnifica, and P. succedanea occur in sympatry on the island of Hawaii (Big Island), but each species differs in behavioral characters: P. kolea utilizes leaves of seedlings and forms a serpentine mine, whereas the latter two utilize leaves of larger plants, and form linear or serpentine to blotch mines. More broadly, leaf mine forms and diagnostic characteristics of the Myrsine-feeding species complex of Philodoria (as currently known) are reviewed and illustrated.