Xpost. I believe that this is a Katydid nymph. ID welcome. If it had rested in the center of the leaf, I likely would not have noticed it. It's camo patterns nicely blend in with the leaves, but its chosen position on the leaf gave it away.
Note the long antennae folded underneath the body. When I started they were under, later shots show them hanging down, and when I finished they were tucked back under.
7/9 note: I tried to find it the last two days, to no avail. If it had moved while I went to get my camera, I doubt the picture below would exist!
Katydid Nymph on Swamp Milkweed by
Roger