The genus to which this very interesting species belongs differs so widely from the rest of the Cynipidæ that it has been separated from the them as a sub-family, under the title Ibaliinœ. Its members can be readily recognized by the cultriform abdomen and more strongly veined wings, as well as by their greater size. The cultriform—i. e., knife-shaped—abdomen is in itself remarkable enough to attract the attention of all who may chance to see the insects.