(no subject)

Here is something about D&D that confuses me. There are insectoid monsters like hook horrors or umber hulks, and yet you never hear about them really having different looking larvae; presumably they just hatch looking like cute hulklets or something.

And then there are insectoid monsters like the maggot like Kyuss worms, rot grubs, or carrion crawlers, where they sure sound like larval forms of something, but then you never get to see an adult - okay so carrion crawlers are supposed to be the adult forms or something. Is it just like bot flies where the adults exist for a week or so worth of mating and then die, or could there be something like whatever adult rot grubs are lurking around the corner waiting to clobber and eat halfling rogues or whatever?