Megaselia larvivora Disney, n. sp. is described from a series reared from the caterpillars of Acharia stimulea Clemens and Lithacodes fasciola Herrich-Schaffer feeding on Quercus alba Linnaeus. The fly closely resembles M. fisheri (Malloch), whose recognition is clarified. Observations from the rearing of Megaselia larvivora Disney, n. sp. are reported.