Hermit crabs are decapod crustaceans of the superfamily Paguroidea [1], not closely related to true crabs. Most hermit crabs salvage empty seashells to shelter and protect their soft abdomens, from which they derive the name "hermit". There are about five hundred known species of hermit crabs in the world, most of which are aquatic, living at a range of depths from shallow coral reefs and shorelines to deep bottoms, although some species are terrestrial. A number of species, most notably king crabs, have abandoned seashells for a free-living life; these species have forms similar to true crabs and are known as carcinised hermit crabs. Hermit crabs live in the wild in colonies of 100 or more, and do not thrive in smaller numbers

Usually the entire body of Crabs is covered with a hard, calcified armour.
The Hermit Crab however lacks this protection on the hindmost part of its body, the abdomen, which is soft and vulnerable.


It protects its abdomen, which contains such important organs as the liver and the gonads, by inserting it into a gastropod shell
For this purpose the abdomen is bent, so that it fits in the curvature of the snail-house.
The outer bend of the abdomen bears some little appendages which enable the crab to hold on to the inside of the shell. The reduced 4th and 5th pairs of legs serve the same purpose
When walking the animal drags its house along. In water the weight of the shell is diminished by the upward pressure and so the Hermit Crab, in spite of its burden, can zealously run about
In case of danger the Hermit Crab withdraws into the shell as deep as possible. In the shell there is no room for two big pincers. Therefore the Hermit Crab has but one. When hiding in the shell it uses this pincer to guard the entrance.
When the crab grows and does not fit in its shell any longer, it looks for a bigger one. The original occupant, if still present, is picked out. Then, quickly and nervously, the crab moves over into its new home.


Often a colony of little polyps grows upon the surface of a Hermits's shell and forms a rough, brown layer on it. A bald patch indicates the spot that touches the substratum when the shell is being dragged along.
The polyps profit by the crumbs of the Hermits's meals and in turn the hermit profits by the protection given by the nettle-cells of the polyps.
Sometimes the Hermit Crab bears Sponges or Sea-anemones on its shell. Besides giving protection these guests give some useful camouflage. When moving into a new shell the crab can remove these from the old one and transplant them.
Pious men used to withdraw into the desert in order to service God in strict solitude. They used to live in a cave or in a little house all by themselves. They were called "hermits" ("eremos" is Greek for "desert"). Hence this name for the funny crab that lives all alone in its self-chosen hermitage.

Molting is a natural process for hermit crabs. In order for a hermit crab to grow it must molt. Molting may occur once a year for larger hermit crabs or once every few months for smaller (tiny crabs).
To know if your hermit crab is preparing to molt look for these signs:

1. The hermit crab will probably become lethargic (it won’t move much).
2. Your hermit crab will start digging.
3. The hermit crab’s coloring may become ashy, the coloring probably won’t be as vibrant.
4. Your hermit crab will probably eat a lot of food and drink a lot of water.
5. The hermit crab may develop some eye crust or the hermit crab’s eyes may look cloudy. This will go away after a molt.
6. Your hermit crab will develop a molt sac. This molt sac holds water and helps to break the exoskeleton when the hermit crab actually molts. The molt sac doesn’t store food.
7. If your hermit crab is missing a limb it will probably develop a gel limb. Once your hermit crab molts the missing limb will be regenerated, but it may be smaller than the original.

If you notice these signs you may want to isolate your hermit crab in what we call an isolation tank. This is usually a smaller tank with lots of moist sand or eco earth, some water (both saltwater and dechlorinated water), food, and a hiding place. Make sure that the humidity is 78-80% and the temperature is around 78-80 also. Some of us, myself included, allow their hermit crabs to molt in the main tank without problems. This is really a personal choice. If you don’t have a good isolation tank with gauges and proper conditions then you should probably leave them in the main tank to molt. Moving them into a plastic box without good heat and humidity really isn’t good.
The hermit crab molting process may take several weeks to several months. Your hermit crab should dig under the substrate when it’s actually going to molt; if it doesn’t you may be using the wrong kind of substrate. When a hermit crab molts above ground it is called surface molting. Gravel, rocks, wood chips, and pebbles are not good molting substrates. It is better to use sand, forest bedding or eco earth as a substrate in your tank. Sometimes a hermit crab will surface molt even with the right tank conditions. If a hermit crab surface molts in your main tank I would recommend isolating the hermit crab in its own tank immediately. Move the exoskeleton with the hermit crab into isolation. When a hermit crab molts on the surface other hermit crabs may attack it. Since the hermit crab is very soft immediately after the molt it will not be able to protect itself from other hermit crabs.
Once your hermit crab has dug under the sand avoid the urge to dig it up to check on it. Leave your hermit crab alone to molt. Keep the tank warm, humid, and dark. Your hermit crab knows how to molt, there is nothing you can do to help. Your hermit crab may be under the substrate preparing to molt, molting, and recuperating post-molt for up to eight weeks. I know, that’s a long time to leave them alone. Larger crabs will typically take longer to molt than smaller hermit crabs. When your hermit crab resurfaces it will be very hairy, have very sharp nails, and if it was being provided a good diet its coloring will probably be very vibrant. Here is a really good picture of a hermit crab’s sharp nails after a molt.
When your hermit crab molts it sheds its exoskeleton like a snake. It then eats its exoskeleton post molt to help it recover. Don’t freak out if you find hermit crab limbs in your tank, it’s probably hollow exoskeleton that your hermit crab didn’t eat. Leftover exoskeleton that your freshly molted hermit crab didn’t eat can be given to your other crabs, it’s good for them! It’s also a good idea to keep other calcium sources in your tank for fresh molters; cuttlebone, crushed oyster shell, and eggshells are good sources of calcium for your hermit crabs.
It will usually take your hermit crab several days to a couple of weeks to fully harden and be active again. If you isolated your hermit crab, you don’t want to put it back into the main tank until it is eating regular food and climbing around the isolation tank like it wants to escape. You will probably find that your hermit crab is very shy post molt and seems like it is afraid of its own shadow, this is normal and it takes about a month for the hermit crab’s normal personality to return.
Just a warning. Many new crab owners think that their hermit crab is dead when it has actually molted. If you come across a crab that looks like it has fallen out of its shell check the shell carefully to see if in fact there is a smaller crab tucked in the shell. When a hermit crab has molted the soft abdomen will not fall out of the shell, only the hard exoskeleton will shed.

Crabby by Nature

The hermit crab makes a great social pet.
Public awareness of hermit crabs as pets is growing, but not many know much about their nature, their place in the ecosystem and the means of proper hermit crab keeping. It's important to understand their nature to properly care for hermits. Land hermit crabs come from tropical regions of the globe, including the Caribbean, South and Central America and parts of Australia. They are born in the ocean near the shore. As they develop, they come ashore to find abandoned small animal shells to inhabit. They have been found in mountainous areas at elevations of up to 3,000 feet. They also have been found living in trees. Hermit crabs have been observed climbing 60-foot cliffs! Hermit crabs live in colonies of up to 100 or more. They are social creatures and do best when living in groups. If you're considering getting a hermit crab as a pet, purchase two or more so your crabs won't be lonely. Land hermit crabs are nocturnal creatures. The midday tropical sun is a danger to them; consequently, the daytime is their quiet time. Hermit crabs are social creatures (belying their name) that seldom fight among themselves. They've been observed communicating to one another by making sounds referred to as chirping. Hermit crabs prefer shells that fit snugly, because a snug-fitting shell protects their soft abdomen and also helps prevent evaporation of moisture on their bodies. Hermit crabs' lungs aren't as efficiently developed as those of other land-based air-breathing creatures, and they require a certain amount of moisture retention for their lungs to operate properly. If hermit crabs become too dry, they can suffocate. If a hermit crab inhabits a sufficiently snug shell, it will keep a small reservoir of water inside for drinking and breathing purposes. As hermit crabs grow, they shed their skin, much like a snake or reptile. If they have any broken or missing limbs such as legs or claws or even eyes, they will regenerate at this time. Their general level of activity will slow down considerably; they may even stop eating prior to this process, known as molting. The crabs will bury themselves in sand as means of protection during this vulnerable time and will stay there for up to a month while the new skin hardens. The crabs need extra calcium at this time to help in the development of the new skin and will actually eat the old skin after shedding it to gain extra calcium.
The Hermit Crab
Hermit crabs do not have their own shells and must live in shells that other animals once used. They do not have the same number of walking legs as real crabs. They have a huge right claw that they use to block the entrance to the shell when a predator threatens. As hermit crabs outgrow their shells, they must look for a new one