Dead or alive?  And what is it?  Can you address either question?

I know definitively the answer to the first question; as to the second one, I have only a guess, one I am investigating.

More photos and information are forthcoming.

[the larger versions of this picture are quite presentable and provide some clues as to the identity of this large and impressive critter; btw, I found it in this condition lying on the patio after I arrived home this evening; it was just outside the bedroom doors; my investigation promptly followed]

[Update] This is a female woolly gray moth (a.k.a. pine barrens lycia; Lycia ypsilon), and she was in fact alive—just stuck on her back.