Crayfish

Crayfish (Fr. écrevisse), the name of freshwater crustaceans closely allied to and resembling the lobsters, and, like them, belonging to the order Macrura. They are divided into two families, the Astacidae and Parastacidae, inhabiting respectively the northern and the southern hemispheres.

The crayfishes of England and Ireland (Astacus, or Potamobius, pallipes) are generally about 3 or 4 in. long, of a dull green or brownish colour above and paler brown or yellowish below. They are abundant in some rivers, especially where the rocks are of a calcareous nature, sheltering under stones or in burrows which they dig for themselves in the banks and coming out at night in search of food. They are omnivorous feeders, killing and eating insects, snails, frogs and other animals, and devouring any carrion that comes in their way. It is stated that they sometimes come on land in search of vegetable food.  
  
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Crayfish (Cambarus sp.) from the Mississippi River. (After Morse.)  
  
On the continent of Europe, Astacus pallipes occurs chiefly in the west and south, being found in France, Spain, Italy and the Balkan Peninsula. It is known in France as écrevisse à pattes blanches and in Germany as Steinkrebs, and is little used as food. The larger Astacus fluviatilis (écrevisse à pattes rouges, Edelkrebs) is not found in Britain, but occurs in France and Germany, southern Sweden, Russia, &c. It is distinguished, among other characters, by the red colour of the under side of the large claws. It is the species most highly esteemed for the table. Other species of the genus are found in central and eastern Europe and as far east as Turkestan. Farther east a gap occurs in the distribution and no crayfishes are met with till the basin of the Amur is reached, where a group of species occurs, extending into northern Japan. In North America, west of the Rocky Mountains, the genus Astacus again appears, but east of the watershed it is replaced by the genus Cambarus, which is represented by very numerous species, ranging from the Great Lakes to Mexico. Several blind species inhabit the subterranean waters of caves. The best known is Cambarus pellucidus, found in the Mammoth Cave of Kentucky.

The area of distribution occupied by the southern crayfishes or Parastacidae is separated by a broad equatorial zone from that of the northern group, unless, as has been asserted, the two come into contact or overlap in Central America. None is found in any part of Africa, though a species occurs in Madagascar. They are absent also from the oriental region of zoologists, but reappear in Australia and New Zealand. Some of the Australian species, such as the “Murray River lobster” (Astacopsis spinifer), are of large size and are used for food. In South America crayfishes are found in southern Brazil, Argentina and Chile.

(W. T. Ca.)

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