Sleeping shrimp is crayfish. Crayfish like to sleep, so it is called sleeping shrimp. Distribution: Eurasia, Rocky Mountains in North America, Southern Hemisphere and other fresh water areas. The general name of freshwater species in the suborder crayfish of Decapoda. The body is large and cylindrical, the shell is firm and thick, the head and breastplate are slightly flat, the front edge does not heal with the front plate of the mouth, and the side edge does not heal with the abdominal shell of the chest and the base of the chest limb, except for crayfish. The neck groove is obvious. There are five pairs of appendages on the head: the first two pairs are developed tentacles. There are 8 pairs of appendages in the chest: the first 3 pairs are palatal feet, which form mouthparts with the rear 3 pairs of appendages of the head; The last five pairs of feet have crawling and predation functions. The first three feet are pliers, and the 1 pair is particularly developed to defend against the enemy. The last two pairs of feet are claw-shaped The abdomen is short and there are 6 pairs of appendages: the first 5 pairs are swimming feet, which are underdeveloped; Finally, 1 pair is a tail limb, which combines with the tail segment to form a developed tail fan. All the steps are single, and the first three pairs are chelated, among which 1 pair is particularly strong and thick, so it is called crayfish. The last two pairs of feet are simple claw-shaped. Gills are filamentous gills. Distributed in running water, water with high dissolved oxygen content, great transparency and fresh water quality. There are about 400 species of crayfish belonging to 5 families, mainly living in fresh water. Among them, the marine crayfish family (38 species belonging to 9 genera) and the saw-edged crayfish family (2 species belonging to 2 genera/kloc-0) belong to the marine type, with the front edge of the head and breastplate healed with the anterior plate of the mouth, the abdominal nail of the last thoracic segment healed with the previous segment, and the basal and seating segments of the second to fifth pairs of feet did not heal. Although the number of species is small, some species have important economic value. Crayfish prefer shade to light. When the light is weak or dim, they climb out of the cave and usually cling to aquatic plants or suspended substances in the water, showing a "sleeping" shape. When the light is strong, it sinks into the water or hides in caves, and there is a phenomenon of vertical movement day and night. Crayfish has a wide range of requirements for water bodies, and can survive in lakes, rivers, ponds, canals and paddy fields, and has strong anti-pollution ability, even in some water bodies where it is difficult for fish to survive. Many kinds of crayfish produced in fresh water have economic value and can be eaten. Artificial farming has developed rapidly.