I know very little about thermodynamics in practice, but would it make sense for hain to have capillaries in the outer layers of their exoskeleton to help cool off? It would mean they would bleed a lot more if you cracked their shells, but it wasn't as if that didn't hurt anyway.

Or, perhaps panting like dogs, would that help?

Cold-blooded?

Bah, I'm clutching at straws. I shouldn't have said anything.