No,it's molting, don't both him or her. Five times during their caterpillar life, caterpillars outgrow their skin, shed and usually eat the old skin, then become active again and resume eating.

You may note sloughed skin behind your caterpillar pretty soon. When they're actively shedding, you may notice your caterpillar's mouth protruding.

Sherry

Thanks. That is very interesting.