The nonphotosynthetic orchid Gastrodia elata Blume (Orchidaceae) is a mycoheterotroph associated with the wood-decomposing fungus Armillaria mellea. Here, we report the symbiotic and parasitic associations of some insects with this orchid. The flowers are nectarless and were visited by females of a halictid bee, Lasioglossum sp. The bees entered the tubular flower and collected the tissue from the orchid’s labellum. Pollinia were attached to the hind thorax of the bee and transported to the stigma of receptive flowers. The stems and corms of the orchid were infested by two rare dipterans, Azpeytia shirakii Hurkmans (Syrphidae) and a new genus and species of scatophagid, Orchidophaga gastrodiacola n. sp. M. Kato. Adult flies of the latter species laid eggs in the flower. The hatched larvae infested the immature ovary, bored downward into the flowering stem, and occasionally entered the underground corms. The high rate of infestation by these dipterans suggests that the robust flower stem of the orchid has evolved as counteradaptation against these particular stem-boring dipterans. A molecular phylogenetic analysis suggests that O. gastrodiacola belongs to Delininae, which is one of the basal groups of Scatophagidae.