Can I put a hermit crab back in its shell?

Yes, but you must put him back in his shell IMMEDIATELY before he dries out. If he is unable to do it himself (too weak, unresponsive, etc.) look up videos of how a crab changes shells, and how he positions himself into the new shell. read more

A hermit can choose to go back in it's shell, or move to a new one. They can survive without claws but it can make climbing and digging hard for them, if yours loses a claw he can possibly grow it back. read more

Your crab might be molting - Sometimes a crab will come out of its shell to molt, though this is also unusual unless the crab is stressed. In any case, when a hermit crab is out of their shell, the crab is very stressed and also very vulnerable. read more