The Collaborative International Dictionary of English v.0.48:

Wasp \Wasp\, n. [OE. waspe, AS. w[ae]ps, w[ae]fs; akin to D.
   wesp, G. wespe, OHG. wafsa, wefsa, Lith. vapsa gadfly, Russ.
   osa wasp, L. vespa, and perhaps to E. weave.] (Zool.)
   Any one of numerous species of stinging hymenopterous
   insects, esp. any of the numerous species of the genus
   Vespa, which includes the true, or social, wasps, some of
   which are called yellow jackets.
   [1913 Webster]

   Note: The social wasps make a complex series of combs, of a
         substance like stiff paper, often of large size, and
         protect them by a paperlike covering. The larvae are
         reared in the cells of the combs, and eat insects and
         insect larvae brought to them by the adults, but the
         latter feed mainly on the honey and pollen of flowers,
         and on the sweet juices of fruit. See Illust. in
         Appendix.
         [1913 Webster]

   Digger wasp, any one of numerous species of solitary wasps
      that make their nests in burrows which they dig in the
      ground, as the sand wasps. See Sand wasp, under Sand.


   Mud wasp. See under Mud.

   Potter wasp. See under Potter.

   Wasp fly, a species of fly resembling a wasp, but without a
      sting.
      [1913 Webster]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Digger \Dig"ger\, n.
   One who, or that which, digs.
   [1913 Webster]

   Digger wasp (Zool.), any one of the fossorial Hymenoptera.
      [1913 Webster]

WordNet (r) 3.0 (2006):

digger wasp
    n 1: solitary wasp that digs nests in the soil and stocks them
         with paralyzed insects for the larvae