Maybe they don't seem crabby because they are not true crabs. Their abdominal legs differ: a hermit's final two pairs of legs are modified to hook into their mobile-home shell--helping, along with the abdomen's coil, to hold the animal in place.
With their nether bits tucked away, you might wonder how hermit crabs mate (you were wondering this, right?). It's all about timing: hermit crabs have to hook up while a female is molting.
|Itty bitty hermit crabs|
Photo by Jeremiah Blatz
When the female finally molts, the mating makes them vulnerable and hasty. Both animals pull nearly out of their shells, and the male quickly deposits sperm on the female's abdomen. She'll later use the sperm to fertilize her eggs as they are laid.
Eventually the hatched young leave their mother's shell in search of suitable lodging in an unoccupied shell--a lifelong occupation as the little animals molt and grow.
Have you ever encountered hermit crabs--little or big--on a beach or tide pool?