These larvae feed on wild grape, and although I've searched wild grape vines for years I had never seen these guys,until today, though they are considered common. I first found this one on June 20th when it was an early instar, looking very different https://pbase.com/laroseforest/image/171734783)/ I went back to see if I might re-locate it again and to my surprise I did, in the final, spectacular instar.

By the way, the head is tucked into the body, the part clinging to the leaf with the big "eye" is the rear end.