CRAYFISH, the name of freshwater Crustacea, closely allied to and resembling the lobsters, and, like them, belonging to the order Decapoda. They are divided into two families ; the Asta cidae and Parastacidae, inhabit ing respectively the northern and the southern hemispheres.
The crayfishes of England and Ireland (Astacus pallipes) are generally about 3 or 4 in. long, of a dull green or brownish colour above and paler brown or yel lowish 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 feed ers, 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.
Other species of the same genus are found on the continent of Europe and as far east as Turkistan. 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 Cambarus, which is represented by 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. 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 "Mur ray 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. C.)