What scares me is in the end the caterpillar seemed to figure out the guy was only touching him to make him squeal and knew that if it stopped squealing, the guy would stop fucking with him.
the 'eat leaves/dont get eaten by birds' mental capacity of a caterpillar understands the concept of curiousity and novelty enough to stop itself from being that to a wierd hairless monkey after realizing it probably wont get eaten.
or
whatever muscles it uses to make that noise cant keep going continuously.
The caterpillar's just starting to realize that this isn't a threatening touch. This advanced science classroom I saw once had Madagascar Hissing Cockroaches that just didn't hiss anymore because they had been handled so much. The caterpillar thing may become totally accustomed eventually as well.