Euptoieta claudia (Variegated Fritillary).
Size: approx. 50 mm. Photo: 05/26/12, noon.

The Variegated Fritillary (Euptoieta claudia) is a permanent resident of the Southern US. They are nomadic and use numerous hostplants. They are difficult to approach and this one moved its wings most of the time which made it difficult to take a decent photo.  

bug guide (this photo):