Rhus gall aphids (Fordinae : Melaphidini) have a disjunct distribution in East Asia and North America and have specific host plant relationships. Some of them are of economic importance and all species form sealed galls which show great variation in shape, size, structure, and galling-site. We present a phylogeny incorporating ten species and four subspecies of Rhus gall aphids based on 1694 base pairs of nuclear elongation factor-1α (EF1α) and mitochondrial cytochrome oxidase subunit II (COII) DNA sequence data. The results suggest that Melaphidini is monophyletic and at the genus level, Schlechtendalia, Nurudea, and Floraphis were each monophyletic. Kaburagia and Meitanaphis were not monophyletic and therefore inconsistent with the current classification. The North American sumac gall aphid, Melaphis rhois, was most closely related to the East Asian Floraphis species, although this was poorly supported. The conservation of gall morphology with respect to aphid phylogeny rather than their host plants suggests that gall morphology is largely determined by the aphids. While there is no evidence of strict co-speciation between the aphids and their primary host plants, switching between recently diverged host plants may be involved in the speciation process in Melaphidini.