New host and distribution records are presented for the following leaf-mining flies: Chirosia gleniensis (Huckett), C. pusillans (Huckett), C. spinosissima (Malloch), Pegomya atlanis Huckett, P. bicolor bicolor (Wiedemann), P. flavifrons (Walker), P. solennis ssp. rumicifoliae Huckett (Anthomyiidae); Neochirosia nuda (Malloch), Parallelomma vittatum (Meigen) (Scathophagidae). The fern gall inducer Chirosia betuleti (Ringdahl) is newly reported from Athyrium asplenioides var. angustum (Willd.) T. Moore in Massachusetts, and parasitoids and other associates are discussed for Gimnomera cerea (Coquillett) (Scathophagidae), which feeds in seed capsules of Pedicularis canadensis L.