This shows the exceptional camouflage of this species. They either feed on the edge of the leaf as here, or they cut a hole in the middle of a leaf and feed there (as in an earlier photo I posted). Either way, they look like the dead edges of the leaf. The inset of this photo shows the basswood leaf with the caterpillar taken from a distance. You can see the caterpillar is the brown dead-leaf-edge mimic at the top end!