Legs, usually referred to as the lower limbs of the human body, one of the functions is walking. Broadly speaking, it refers to its structure to support, and for animals, it is usually approximately cylindrical. Due to the need to disperse gravity, the ends of the legs typically form a wider structure, such as the feet of a human. Anatomically, the animal's legs have another important function, which is to move themselves (in addition to walking, swimming, etc.). The majority of animal legs are even in number. The leg refers to the limb from the ankle to the base of the thigh. The legs of arthropods can be classified according to the number of segments, and can also be classified according to the classification of limbs such as single limbs or both limbs. The limbs of arthropods other than the crustacean are single-limb.