Found several of these on my walk today, on small bitternut hickory saplings. Likely hickory hairstreak, but could be banded hairstreak which also feeds on hickory. I am told that they larvae of both species are very similar.

To see a hickory hairstreak butterfly: http://www.pbase.com/laroseforest/image/114687194

To see a banded hairstreak butterfly: http://www.pbase.com/laroseforest/image/113442814