(Freehold, NJ) Green butterfly
You have a Luna Moth.
These are beautiful moths! They are in the Silk moth family (Saturniidae) The larvae become large green caterpillars, over 2″ long. The caterpillars feed on many trees including birch,
black gum, hickory, persimmon, sweet gum and walnut. Cocoons are hidden in leaf litter in the winter.
Many are seeing these right now….except me…I want to see one too!
What little the caterpillar would eat would not damage the hickory in any way. They are not a pest of any sort. So few of caterpillars end up on any one tree that there is no significant damage