This study encompasses three trophic levels, including description and observations of a butterfly caterpillar, its host plant, and two parasitoids, one of which is described here as a new species. We describe the immature stages and larval and adult behaviors of the butterfly Eryphanis greeneyi Penz & DeVries, 2008 (Lepidoptera: Nymphalidae) from the east Andean slopes of Ecuador. We identify Chusquea cf. scandens (Poaceae: Bambusoideae) as the larval food plant and review host associations in the genus Eryphanis and related taxa. We compare the morphology of E. greeneyi caterpillars to related taxa feeding on Chusquea and discuss the function of anal combs and associated frass throwing behavior. We describe a new species of braconid wasp Protapanteles eryphanidis sp. n. Whitfield and a tachinid fly, Winthemia sp. nr. analis, reared from field-collected larvae of E. greeneyi and evaluate their taxonomic position and association with E. greeneyi.