It's a luna moth, Bob. Hopefully, it just needs to find a place to make its cocoon.
Have you tried putting it back on the tree?
Sherry

If it cannot move, put it in a smooth bottom container. If it has no health/parasite issues, it will pupate without its flimsy cocoon.

ID trick I tell people is green face=luna, brown face=poly

KC

Are those parasitic cocoons near the head of the cat?
'Hope they aren't!
I just look for the yellow line, KC - yellow line, luna - no yellow line, poly.
Sherry

Those look like tachinid fly eggs, to me. The adult glues the little eggs to the outside of the host caterpillar, often close to the head capsule, I think. Anyhow, when the eggs hatch, the larvae will chew its way to the innards of the host.

Tachinids don't make little cocoons when they are ready to pupate.

But my way is clearly better. ;D

All my lunas are 5th instar right now. I wanted to refresh my memory on what a 2nd instar looks like. I did a Google images on "luna moth caterpillar." Quite a few of the "luna" cats don't seem to have a stripe down their side or a green face. Must be some local variations ;)