Tiphia vernalis-- This small, parasitic wasp of Japanese beetle grubs
resembles a large, black, winged ant. Its current distribution is
believed to be throughout the Northeastern United States and south to
North Carolina.

After a brief period of feeding and mating during the spring, the
female wasp digs into the soil, paralyzes a beetle grub by stinging,
and then deposits an egg on the grub. When the egg hatches, the
emerging wasp larva consumes the grub.

Food sources: Adult wasps of this species feed almost exclusively on
the honeydew of aphids associated with the leaves of maple, cherry,
and elm trees and peonies. In North Carolina, the nectar of tulip
poplars has been found to be an important food source for the adult
wasps.
http://doityourself.com/pest/biological_controls.htm