John,
I have an arbor with a passion vine on it and these catipillars were all over it!
It was disgusting.
i sprayed the vine the best I could with an organic spray pesticide from HD, there aren't as many on it now.
THey were even on my house and windows.
Ewwwwwwwwwww

Oh, they make one of my favorite butterflies so I let them munch the vine all they want. They only stay this size for about a week and then wander off to pupate and then turn into butterflies. The adults are flitting about my yard now.