Land hermit crabs are popular creatures found in most pet stores. It is their small size and general easy care that make them so popular for smaller children. There are two main species that can be found within the US: Coenobita clypeatus, also known as the Purple Pincher, and Coenobita compressus who’s common name is the Ecuadorian Crab.
Just as the name implies the large claw on these crabs is generally purple and sometimes has a lighter tip. Another characteristic of the Purple Pincher is a larger number of setae on it’s exoskeleton. When you look at the legs of the crab you will see lots of dots, they are the hair-like filaments known as setae. The eyes of these crabs are rounded and sometimes have a flattened lower portion to the eye. Their heads are usually brown/tannish with darker purple/brown legs. Smaller crabs tend to have a light head with a dark spot in the center.
Found inland away from the seashore, these crabs usually live off of whatever falls to the forest floor.
Unlike their counter-parts, these crabs have far less setae on their exoskeletons, only small areas on the front edges of both claws. The eyes of the Ecuadorian are elongated, and they usually have stripes on the sides of their head. Unlike the Purple Pincher who has lighter tips on its legs, this crab has darker reddish tips on lighter orange/tannish legs.
Native to Ecuador, these crabs live near the seashore around tidal pools and high-tide-zones. In order to live in captivity it is essential that seawater be provided for them. Synthetic sea salt can be found in pet stores to compensate for not living near the ocean.
You can have both species in the same habitat without worry. Just provide a dish of saline water and a dish of fresh water and both will cohabitate nicely. It is important that you never keep a single crab, always at least two. Despite the misleading name, hermit crabs are not hermits. They are very social and will become depressed and sometimes die if left alone for too long.
If you have a crab and notice it isn’t active, try purchasing another crab. Usually in a matter of days you will see a marked increase in activity, including more chirping noises at night as they talk to each other. Another reason for inactive crabs is the temperature in the habitat is too low. Try purchasing a heat lamp, it doesn’t need to be any higher than say a 75 watt bulb. It is important that the temperature not dip below 70 F as the crabs will slow down, stop eating and usually die.
Note: Never put large crabs in with small crabs. The larger crabs will usually kill the smaller crabs as they are more aggressive and more powerful overall.
I've had hermit crabs since 1999, and my knowledge came from a book I read way back then that I no longer own, so I can't tell you the name as a reference, only that it was a Hermit Crab pet care book.