The Development of the Locust Jumping Mechanism: II. Energy Storage and Muscle Mechanics

Abstract

1. In an escape jump, the adult locust extensor tibiae muscle produces more than twice the specific energy output of the fourth instar muscle. 2. If forced to jump repeatedly, the extensor muscles of hoppers and adults produce the same specific energy output. 3. In escape jumping, specific energy production increases with age within an instar, but this does not seem to be the case in repeated jumping over a 10-min period. 4. Adult locusts have thicker cuticle, including thicker semilunar processes, than hoppers. They also have relatively larger extensor apodemes. The cuticle thickness of all instars increases with age up to apolysis or maturity. 5. The fourth instar extensor muscle has a lower angle of pennation and relatively longer muscle fibres than the adult muscle. 6. The stiffness of the semilunar processes increases with age both within and between instars, so that the mature adult leg has the highest energy storage capacity. 7. To produce the required amount of energy storage, the adult muscle fibres must shorten slightly more than those of the fourth instar, but they must produce more than twice the force per unit area. 8. The strain on the apodeme is similar in adults and hoppers, and greater at the distal than at the proximal end.