Mystery Worm

I noticed a green worm on my shirt when I came inside from checking my robins.

He has a brown head. The stripe down his back was pulsing between dark green and light green as he crawled over my hand. I noticed this happening even when he was sitting still.

I noticed the silk he was leaving on me came out of his mouth.

My mom and I were not able to figure out what kind of a worm (larva) it was. If you know, could you let us know in the commnets?