where the previously advancing front hoof touched the ground. The more the rear hoof oversteps, the smoother and more comfortable the walk becomes. Individual horses and different breeds vary in the smoothness of their walk. However, a rider will almost always feel some degree of gentle side-to-side motion in the horse's hips as each hind leg reaches forward. The fastest "walks" with a four-beat footfall pattern are actually the lateral forms of ambling gaits such as the running walk, singlefoot, and similar rapid but smooth intermediate speed gaits. If a horse begins to speed up and lose a regular four-beat cadence to its gait, the horse is no longer walking but is beginning to either trot or pace. Elephants Elephants can move both forwards and backwards, but cannot trot, jump, or gallop. They use only two gaits when moving on land, the walk and a faster gait similar to running. In walking, the legs act as pendulums, with the hips and shoulders rising and falling while the foot is planted on the ground. With no "aerial phase", the fast gait does not meet all the criteria of running, although the elephant uses its legs much like other running animals, with the hips and shoulders falling and then rising while the feet are on the ground. Fast-moving elephants appear to 'run' with their front legs, but 'walk' with their hind legs and can reach a top speed of . At this speed, most other quadrupeds are well into a gallop, even accounting for leg length. Walking fish Walking fish (or ambulatory fish) are fish that are able to travel over land for extended periods of time. The term may also be used for some other cases of nonstandard fish locomotion, e.g., when describing fish "walking" along the sea floor, as the handfish or frogfish. Insects Insects must carefully coordinate their six legs during walking to produce gaits that allow for efficient navigation of their environment. Interleg coordination patterns have been studied in a variety of insects, including locusts (Schistocerca gregaria), cockroaches (Periplaneta americana), stick insects (Carausius morosus), and fruit flies (Drosophila melanogaster). Different walking gaits have been observed to exist on a speed dependent continuum of phase relationships. Even though their walking gaits are not discrete, they can often be broadly categorized as either a metachronal wave gait, tetrapod gait, or tripod gait. In a metachronal wave gait, only one leg