Hermit crabs, members of the families Paguridae, Diogenidae, and Parapaguridae share the common feature of having their soft, uncalcified abdomens elongated and usually hidden inside of an empty snail shell or other hollow object. The king crabs, family Lithodidae (below) are very closely related to hermit crabs. Hermit crabs spend a great deal of their time searching for new homes. They can often be observed 'testing' new snail shells, first reaching inside to insure they are empty, lifting the shell to test weight and portability, then quickly switching shells if the new home is approved. They usually ignore shells with a live snail inside although will often forcibly evict other hermit crabs who have the misfortune of carrying a nicer shell and being smaller than the aggressor