I just did a quick search. I think Murray was on the right track but Datana angusii has red legs and more distinct white markings from what I can see.
http://bugguide.net/node/view/253180/bgpage
Datana intergerrima (Walnut Caterpillar Moth) might be more likely and is correct for the tree species (they feed on hickory, pecan and walnut).
See what you think:
http://bugguide.net/node/view/3234
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