Dryocosmus are a genus of gall wasps. They are cyclically parthenogenetic insects that induce galls on plants in the family Fagaceae. According to recent studies, the genus includes some species previously considered as belonging to the genus Chilaspis, whereas Dryocosmus favus should be excluded of the genus. Dryocosmus and Chilaspis are closely related to the other oak gall wasp taxa (Aphelonyx, Plagiotrochus, Pseudoneuroterus, Trichagalma, and some Neuroterus species)