Pseudopachybrachius basalis.
Size: approx. 5 mm. Photo: 06/12/12, 11 pm.

Pseudopachybrachius basalis can be found in most of eastern and central North America especially in areas with Panicum grasses. 
bug guide (this photo):

Pseudopachybrachius vinctus.
Size: approx. 5 mm. Photo: 09/24/17, 9 pm.

Pseudopachybrachius vinctus feeds on a variety of seeds especially grass seeds. This species is wide spread in the Southeast. The small photo was taken on 07/30/12. 

bug guide (this photo):
bug guide (small photo):