This September 2019 video says about itself:
What’s Inside A Caterpillar ‘Cocoon’
Contrary to popular belief, a chrysalis is not a pouch or a sac —It’s actually the caterpillar’s own body! During metamorphosis, the former caterpillar releases digestive juices that dissolve cells in its muscles, gut, and other organs. Then, special groups of cells called imaginal discs divide over and over again, forming wings and other adult structures.