Cover Caption

Abstract The frog‐legged leaf beetle, Sagra femorata , is notable for its remarkably enlarged hind legs. When faced with external threats, it initiates a stress response by rapidly rotating its hind legs to a specific angle (0°–168.77°). Researchers have revealed that the metacoxa‐metatrochanter joint is a "screw‐nut" structure connected by four muscles, which regulate the rotation of the legs. Further testing using a 3D‐printed model of the metacoxa‐trochanter joint demonstrated its possession of a self‐locking mechanism capable of securing the legs in specific positions to prevent excessive rotation and dislocation. It can be envisioned that this self‐locking mechanism holds potential for application in bioinspired robotics (See pages 1864–1875). Photo provided by Dr. Le Zong.