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Title: Not all oak gall wasps gall oaks: the description of Dryocosmus rileypokei, a new, apostate species of Cynipini from California

item Buffington, Matthew
item MORITA, S. - NCSU

Submitted to: Proceedings of the Entomological Society of Washington
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2008
Publication Date: 1/9/2009
Citation: Buffington, M.L., Morita, S.I. 2009. Not all oak gall wasps gall oaks: the description of Dryocosmus rileypokei, a new, apostate species of Cynipini from California. Proceedings of the Entomological Society of Washington. 111:244-253.

Interpretive Summary: Seed-feeding insects have a major impact on natural and agricultural ecosystems, causing millions of dollars of damage annually. This paper descibes a very unusual species of wasp that is a seed predator in chinquapin shrubs in the mountains of California. The biology of this group of wasps is poorly understood, and this paper helps bring to light their unusual seed-feeding behavior. Biological control practitioners and members of the California Department of Forestry will be interested in the data presented in this paper.

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.