That's a hickory horned devil and they can get bigger than that! They're harmless and don't cause any noticeable damage to there host plants. Here's some more info.

Here is a link that might be useful: http://entnemdept.ufl.edu/creatures/bfly/regal_moth.htm

This post was edited by karalynn on Mon, Aug 19, 13 at 16:45

The moth is awesome too! Don't kill it.