One way I've heard it described is that the caterpillar effectively develops an organ that is analagous to an egg from which the butterfly hatches. Then the res

One way I've heard it described is that the caterpillar effectively develops an organ that is analagous to an egg from which the butterfly hatches. Then the rest of the caterpillar's body becomes food for the newly-hatched bufferfly. This all occurs inside the chrysalis so that we are spared from witnessing the carnage. I have no idea if this is a valid way of looking at it or not, but it's one explanation that I've heard. The appealing part about this is when you realize that some wasps lay their eggs inside other insects, which then become food for the wasp larvae in the same way that the caterpillar's body is supposed to become food for the butterfly.