own galls also, those on the American oaks differing from those on the European species, but some are common to more than one species. The insects which produce
Fig. 51.—An oak-leaf with several kinds of Cynips galls on it: a, gall produced by Cynips scutellaris; b, C. divisa; c, Neuroterus Reaumurii; e, Biorhiza renum; f, Neuroterus ostreus. (Frank.)
the commonest English oak-galls are nearly all members of the Cynipideæ, a group of hymenoptera which lay their eggs in the young tissues of various plants, especially oaks and roses.