Fletcher Wildlife Garden, on a bur oak. I was looking on and under oak leaves for a particular treehopper that likes oaks, when I saw this tiny thing (under 7mm). When I got home I checked some field guides and concluded it was a hairstreak larva (caterpillar). But just to be sure I asked butterfly expert Ross Layberry, and he confirmed it and also told me which species, the Banded Hairstreak, and said it was probably 3rd instar.