Species concepts for Dalmannia, Robertsonomyia, Stylogaster and Zodion (Diptera: Conopidae) of the Nearctic [NE] region are reviewed or revised. Provided are descriptions of new species, with distributional, natural history, host data where available, preliminary phylogenetic analyses with pairwise distances, neighbour-joining and parsimony trees, and illustrated keys to species. Concepts for Zodion have been refined due to many new species: Z. alexanderi, Z. dawkinsi, Z. dillahuntyi, Z. harrisi, Z. hauseri, Z. hirsialiae, Z. hitchensi, Z. lisafyrea, Z. meigeni, Z. oharai. A new species of Stylogaster is also presented: S. beresfordi. The NE region is home to roughly 87 recognized species, listed in the Appendix. Synonyms of Z. fulvifrons Say, (Zodion bistria Walker, Zodion lativentre Graenicher, Zodion sayi Banks, Zodion obscurum Banks) have been synonymized under Zodion intermedium, Banks upon examination of dorsum and by comparing genitalia. An overview of other Nearctic genera (Myopa, Physocephela, Physoconops and Thecophora) is given.