The common name digger wasp is a broad term which may refer to any member of the wasp families that make underground nests:
Bembicidae, including Bembix (sand wasps) Crabronidae, including Oxybelus (spiny digger wasps) Philanthidae, including Philanthus (beewolves) Sphecidae, including Sphex (digger wasps) and Ammophila (sand wasps)