Just like other hermit crabs the small hermit crab lives inside an empty snail shell to protect its soft hind body. The left claw is considerably larger than the right. It's just the opposite by the common hermit crab. Furthermore, the small hermit crab is gray and while the common hermit crab is orange-red. The small hermit crab is a good example of what biologists call an invasive species. Sometimes they are present in huge amounts; other times there are only a few to be found. It's all related to the temperature of the sea water.