As a group, the wasps which inhabit the North American continent have not attracted very widespread interest, despite the excellent accounts of the habits of various species which have been published by such careful observers as the Raus, the Peckhams and other writers.

This, possibly, is due to the fact that relatively few of the numerous species appear to have a very direct relationship with insects that are consided to be of great economic importance. Exceptions to this general rule are found in such genera as Podalonia (Ammophila) and Sphex, which are conspicuous in their activities while hunting for cutworms and in, subsequently, dragging them to their subterranean nests.