They’re more closely related to certain kinds of lobsters than to true crabs. Hermit crabs have a curled tail with a hook that enables their bodies to fit inside these borrowed shells.

Despite their name, mantis shrimp are not true shrimp but a type of stomatopod: a relative of crabs and lobsters that ... peacock mantis shrimp have rainbow shells—usually blue, green, and ...

If you don't have enough crab shells on hand ... it's easy to supplement with shrimp shells. You can also mix and match with ingredients like lobster shells if they happen to be in season.