Molting is a beautiful thing. When your insides start feeling a little too big for their case, you can just crack open your exoskeleton, head capsule and all, and emerge a whole new invertebrate. You get to leave your shed body behind and walk away, freed from all the trappings of your former, smaller life.
… unless, that is, you’re a gum-leaf skeletoniser caterpillar. In that case evolution actually stacks all your old heads on top of your new one and makes you wear them around forever like a macabre stovepipe hat. I don’t know, just go with it, okay?