Hermit Crab Molting
Land hermit crabs, grow just like many other crabs, by shedding their outer skeleton. This is called molting. A hermit crab is most vulnerable during this critical stage of growth, until their new armor hardens. In the wild, hermit crabs to like to molt in the spring but in captivity, they can molt any time of year, for up to a month.
When a hermit crab is ready to molt it becomes very sluggish. They often will try to bury down and hide into or under whatever medium is kept in their cage with them. It is EXTREMELY important that they be kept moist during this time. Keeping a wet sponge can be the difference between life and death to a crab when it is molting.
It might be prudent to even go so far as to separate a molting crab from others. During the molting process a crab will lose it's legs and "shed" it's outer skeleton. We have heard of people even thinking that their crab has died and throwing away the "empty" shell. It is during a molt that broken or missing claws are repaired.