Isodontia auripes (Brown-Legged Grass-Carrier).
Size: approx. 30 mm. Photo: 09/05/11, 11 am.

I believe this is a Brown-Legged Grass-Carrier (Isodontia auripes). It is found in the Easten US. The brown legs are characteristic. They belong to the grass-carrying wasps because they use grass blades to partition cells and form closing plugs in their cavity nests. 

bug guide (these photos):
U Michigan: