Feeding, I believe, on hazelnut, Corylus species, size estimated. I thought at first this was an Elm Sawfly:

and that I had been mistaken about the hostplant. Searching the web, however, I found matching images of Arge pectoralis larvae, and references stating it feeds on Hazelnut and Birch--details on guide page. The larva at lower right is exuding a droplet of defensive secretion, common in sawflies, apparently--see Eisner, For Love of Insects (1), for example.

The North Carolina Arboretum, near Asheville, looks like a great place to look for insects--lots of nature trails, convenient to a visitor's center. This was my first visit--I'll have to go back.