After spinning a cocoon, the caterpillar will make a pre-pupa. A pre-pupa is the phase in which the caterpillar shrivels up and can no longer eat or walk. About four days the the caterpillar forms a pupa. The pupa is the place where the actual moth forms. It will crack out of this case in the spring and then have the trying task of escaping the cocoon.
I usually cut my cocoons open. It makes sure the moth will eclose properly and nothing will happen to it. It also is beneficial when taking photos. I caution beginners not to try it until they have seen someone else do it or have been raising moths for a couple of years.
