HERMIT CRAB. One of a large group of small crabs (q.v.) of the family Paguridle, hav ing the abdominal or tail segments much more largely developed than in true crabs. but un defended by hard plates. and not forming an organ for swimming. The soft and tender tail re quires a protective covering, which the instinct of the hermit crabs leads them to find in some coiled shell of a suitable size. On the slightest alarm the hermit crab retires backward into the shell. guarding the aperture of it with one claw. which is much larger than the other, the hard points of the feet also projecting a little. The whole struc ture of the animal is adapted to such a habita tion. The part which in the lobster becomes a finlike expansion at the end of the abdomen, be comes in the hermit crab an appendage for firm ly holding in the shell; and so well does the hermit crab hold that it may he pulled to pieces. but cannot be pulled out. Some species hare suckers to render the hold more perfect. They often remain in a single shell for a long time, b0 that colonies of ilydractinia and other hy droids grow over a large part of it. Often sea anemone, attach themselves to the shells in which lien nit crabs live, and thus get the benefit of free and rapid transportation. (See COMMEN sAusNt.) A Chinese species is said to carry an anemone on its so that when withdrawn into its shell the anemone forms an effectual stop per to the opening. increase of size, hoacver. ren ders it necessary for hermit crabs to relinquish their shells and seek new ones from time to time, and when thus engaged they are very interest ing animals to watch. They try on shell after shell before finding one that suits them. and they are constantly quarreling savagely over their houses; yet in fact they are great cowards. Her mit crabs are very interesting inmates of the aquarium, but their locomotive habits and their voracity make them unsuitable for an aquarium stocked with valuable animals. They feed on mollusks and other crustaceans, and all the ani mal garbage of the seashore.
The most common Ameriean siss.ies (PagurUS is an interesting object to every visitor of the seashore, and may be found in abundance wherever little pools are left by the tide on a rocky or shelving coast, from Massa chusetts Bay to South Carolina.
This species never reaches a large size. and is usually under an inch in length. It is very
gregarious. and large numbers are usually found together. A closely related larger species Is En pagurus pollicaris, which is found in shallow water from Massachusetts to Florida. inhabiting the shells of Nation and other gastropods. The common European species. Eupagurus Bernhar flux, is also found in somewhat deeper water off the northeastern coast of America. In the tropics some interesting forms occur, including one or two of large size. One of the most interesting is the Diogenes crab (Cernaita Diogenes). which is several inches long when fully extended. It lives on land, and is found in the driest places. us active ns other forms are in the sea. Allied to the hermit crabs are the palm or robber crabs latro) of the East Indies. which live in holes in the ground at the foot of cocoanut palms, on the fruit of which they feed. They do not carry a shell with them. Sec LAND-CRAB.
While the shallow-water hermit crabs are sym metrical behind the thorax, in certain deep-sea forms the abdomen is symmetrical, showing that the ancestors of the ordinary hermit crabs were all symmetrical. Poly/elutes Agassi:ii of the West Indian seas lives in straight tubes of coin raeted sand, the abdomen being symmetrical. This also is the ease with Xylopayurus reetus, living in open tubes of wood or bamboo stem. Tylaspis anomala, inhabiting the South Pacific at a depth of 2375 fathoms, has a shortened but ‘ymmetrical abdomen, with distinct segments and symmetrical legs. Another form (Clurnopagu rus) takes refuge in a sheet or blanket formed by the co•osare of a colony of polyps. It also is symmetrical. The polyp (Zoanthus) is lurked by the crab under its telson by one end and pulled oven its hack by the other, and the two animals. crab and polyp. seem incapable of independent existence. (See CONINfENSALISM.) Hermit crabs have rarely been found in a fossil state, and then only their claws are found preserved. These have been obtained in the Eocene rocks of Hun Consult: Emerton, Life on the Seashore (Salem, 1880) ; Verrill, /mai-iambs 0/ Vine yard Sound (Washington, 1S74) ; Arnold, Sea Peach at Ebb Tide (New York. 1901) ; NlhncEdwards et Bouvier, "Description de, crustaci.s de la famine des Pagurieus pendant l'Exp6dition de la (Memoirs Mascara of Comparative Zoology, Cambridge, 1893).