One of the more interesting facts about the hermit crab is that he is neither a hermit nor a crab. As a pet, he's quite sociable and does well in groups of his own species.
The hermit crab, unlike true crabs, has a long, soft, spirally coiled abdomen terminating in an asymmetrically hooked tail. A true crab has a short abdomen with a large hard shell. They are nocturnal animals, active at night and least active around noontime. They don't bite, but they do pinch and can even draw blood.
There are about 800 species of hermit crabs and can be found all over the world. However, there are only two species usually found in the pet trade: the purple claw crab and the Ecuadorian crab. The purple claw crab is found in south Florida, the Caribbean, Bahamas and West Indies. The Ecuadorian crab can be found along the west coast from Baja, California, to Chile.
Hermit crabs are social animals, but some do show aggression toward one another. The purple claw crab can be a little ornery and may pinch, while the Ecuadorian crab has a sweet, trusting temperament.
To learn more about hermit crabs as pets, see the story Choosing a Hermit Crab