Buffalo Treehopper Nymph

Has that insect caused the damage to the plant?

I don't believe this nymph caused the damage but his mom may have. Treehoppers make a slit in the stem to deposit their eggs. I'm not really sure if those holes are where the eggs were or if they were caused by another insect. It's very tiny damage that didn't seem to effect the plant.

I know next to nothing about insects... are the tree hoppers beneficials?
what do they feed on? tree sap or other insects? I love your photos...awe inspiring!

I wouldn't say beneficial Lori, they take sap from vegetation, especially trees and shrubs. They make little slits in twigs for their eggs and if the slits are towards the end of the twig, the tip may die. Not really a pest that I know of. Some are really shaped neat and some are colorful, so I like them.