Decapod crustaceans (1) (shrimps, crayfish (2), and lobsters (3)) have 14 pairs of "legs", divided into four different groups.|
The first three pairs, just behind the animal's mouthparts (4), are "eating legs" (maxillipeds (5)), used to manipulate food before passing it forward to the mouthparts. They are usually hidden beneath the head/thorax shield (6) (carapace).
Next are five pairs of "walking legs" (pereopods (7)). In some crustaceans, the first pereopod is equipped with a large claw (8). Some pereopods have gills (9) attached near their bases.
Behind these are five pairs of "swimming legs" (pleopods (10)), used for swimming slowly forward. Some crustaceans carry their eggs among their pleopods.
Finally, there is one pair of "tail legs" (uropods (11)) that are part of the tail fan, which is used for sudden backwards flight from predators (12) and other potential threats.