Final answer:
The first pair of walking legs in crayfish, lobster, crab, and their relatives that is enlarged with a terminal claw is called the cheliped.
Step-by-step explanation:
The first pair of walking legs in a crayfish, lobster, crab, and their relatives, that is enlarged with a terminal claw is the cheliped. Chelipeds are specialized legs that are used for capturing and manipulating food, defense, and courtship. They are characterized by their enlarged size and the presence of a pincer-like claw at the terminal end.