Then there is the edible crab, or blue crab, which is common on many parts of our coasts. The edible crab of Europe is somewhat different. You are not likely to meet with the larger examples, which live in deeper water. But even the smaller ones can give a very sharp nip with their great claws, and you will find it as well to be very careful in handling them. The best plan is to seize them with the thumb and finger just behind these claws, then they are perfectly harmless. The larger crabs, which sometimes weigh as much as twelve pounds, are extremely powerful, and in more than one case a man has been killed by them, having been seized by the wrist as he was groping among the rocks, and held in a grip from which he could not break away until he was drowned by the rising tide.
These crabs are captured by means of crab-pots, made of basketwork, which have the entrance so formed that while the crabs can easily enter, they cannot possibly get out again. These pots are baited with pieces of fresh fish, and are then weighted with stones, and lowered to the bottom of the sea among the rocks, at a depth of from three to about twenty fathoms. They are also caught on lines baited with meat. No hook is needed, for the crab clings to the meat till it reaches the surface of the water, when it must be flung into the boat or somehow captured quickly, before it has time to let go and sink.
Some crabs live on dry land, sometimes at a distance of two or three miles from the sea, which they only visit at intervals. Among these are the famous calling-crabs, found in many of the warmer parts of the world. These crabs obtain their name from the fact that one of the great claws of the male is very much larger than the other. So big is it, indeed, that it has to be held aloft over the body when the animal is running, in order to prevent it from losing its balance and toppling over. And as soon as the crab begins to move this huge claw is jerked up and down, just as if the creature were "calling," or beckoning, to its companions. The calling-crabs live in burrows in the sand, which are often placed as close to one another as those in a rabbit-warren.
Hermit-Crabs
Next we come to those small, curious creatures known as hermit-crabs, which form a kind of connecting link between the crabs and the lobsters, for their tails, instead of being firmly soldered down underneath their bodies, are quite free.
But the odd thing about these animals is that their tails have no shelly covering. The front part of the body is protected by a coat of mail, just as it is in all the other crabs; but the hind part is quite bare and soft. The consequence is that a hermit-crab is always very nervous indeed about his tail. He is dreadfully afraid that one of his many enemies may creep up behind, and bite it when he is not looking. So he always tucks it away in an empty shell like that of a whelk or a sea-snail, which he drags about with him wherever he goes!
You may often find these curious crabs by hunting for them in the pools among the rocks at low water. The crab always sits just inside the entrance of the shell, which he closes and guards with one of his great claws. And if you try to pull him out, you will find that you are quite unable to do so, for he has a pair of strong pincers at the end of his body, by which he holds the shell so firmly that you can tear him in two without forcing him to loose his grip.
Sometimes you will find that a sea-anemone has fastened itself to the edge of a shell in which a hermit-crab is living. This is a great advantage to the crab; for while there are many fishes which would be quite ready to crunch him up, shell and all, no fish will ever meddle with a sea-anemone. So as long as the anemone remains on his shell he is perfectly safe.
And this plan is also a great advantage to the anemone, which is sure to get plenty of food without any trouble. For when the crab finds the dead body of some small creature, and begins to pull it to pieces, a quantity of small fragments is sure to float upward in the water. And the anemone catches them with its spreading tentacles and feeds upon them.
The Robber-Crab