Molting, or the process of shedding of the exoskeleton, skin, feathers, etc. is the one simple act hermit crabs perform, that causes their owners to become nervous, panicky, and downright paranoid. If your hermit crab is relatively healthy, you have no cause for concern. Hermit crabs need little help from humans when it comes time to molt; the wild crabs do it all the time. Here's exactly what takes place before, during, and after a molt:
1) Your hermit crab may appear sluggish and will often seek out dark hiding places. It may eat less than usual, and drink more water than normal. If you have more than 2 hermit crabs and you suspect one of them may be preparing to molt, it may be a good idea to set up temporary housing for that crab. Include about 3 inches of sand, plus food and water.
2) You will often find your hermit crab digging holes and burying itself under the sand. If your crab buries itself, leave it alone. Your hermit crab will more than likely be preparing to molt. Never disturb a hermit crab who has "gone under".
3) At this time, pressure is building up under your hermit crab's exoskeleton. Eventually, your crab's exoskeleton will split down the middle, right behind your crab's eyes. He will then work off the skin completely.
4) After the exoskeleton is removed, your hermit crab is a very pale color. Pinkish grey is most common. The texture is very soft and delicate, and the crab must not be handled. Also, it is not uncommon for your hermit crab to eat his shed exoskeleton. I know it sounds gross but the calcium in the exoskeleton will help your hermit crab regain the strength and color of his new exoskeleton.
5) When your hermit crab's new exoskeleton has hardened, he will make his way back to the surface. If he was missing any limbs before, they are intact and good as new now. He will continue to be sluggish for the next few days, up to a week. Then he will continue his normal activity.