LARVA-tar to PUPA-tar (looks like a cacoon). It does make sense. Except for Tyranitar, which is a dinosaur. Sorry about the weird question!
Pupitar is derived from pupa, the stage in some insects between the larval stage and adulthood.
So it is possible that they are based on a bug, but mixed with a Dinosaur/Lizard. It sounds weird, buts that's what evidence leads to.
Hope I helped! :) Source
