Technical Abstract: Cynipini gall wasps are commonly known as oak gall wasps for their almost exclusive use of oak (Quercus spp.) as their host plant. Previously, only three of the nearly1000 species of Cynipini have been recorded from a host plant other than Quercus. These three species are known from western chinquapin (Chrysolepis), chestnut (Castanea) and tan bark oak (Lithocarpus) all lineages of Fagaceae related to Quercus. Here we describe a new, second species of cynipine which attacks Chrysolepis, namely Dryocosmus rileypokei, new species. Unlike D. castanopsidis, which produces a medium sized spherical external gall near the base of the staminate (male) flowers of Chrysolepis sempervirens, D. rileypokei, new species, which attacks the same host, is a predisperal seed predator. Dryocosmus rileypokei creates galleries within the mesocarp wall of the nut and appears to consume all of the endosperm and embryo. Later instar larvae and teneral adults were found within these mesocarp galleries. It appears that from these galleries, the adult wasp eventually chews an exit hole. The host use of the three, non-oak galling Dryocosmus species deviate significantly from the other 22 known species of Dryocosmus; the evolution of host use within this unusual lineage is discussed.