Jumping performance of froghopper insects

Abstract

SUMMARYThe kinematics of jumping in froghopper insects were analysed from high speed sequences of images captured at rates up to 8000 s-1. In a jump, the attitude of the body is set by the front and middle legs, and the propulsion is delivered by rapid and synchronous movements of the hind legs that are 1.5 times longer than the other legs, but are only about half the length of the body and represent just 2% of the body mass. The wings are not moved and the front and middle legs may be raised off the ground before take-off. The hind legs are first cocked by a slow levation of the trochantera about the coxae so that the femora are pressed against the ventral, indented wall of the thorax, with the femoro-tibial joints tucked between the middle legs and body. Only the tips of the hind tarsi are in contact with the ground. In this position, the hind legs stay motionless for 1-2 s. Both trochantera are then synchronously and rapidly depressed about the coxae at rotational velocities of 75 500 deg. s-1 and the tibiae extended, to launch a jump that in Philaenus reaches a height of 700 mm, or 115 body lengths.In the best jumps by Philaenus, take-off occurs within 0.875 ms of the start of movements of the hind legs at a peak velocity of 4.7 m s-1 and involves an acceleration of 5400 m s-2,equivalent to 550 times gravity. This jumping performance requires an energy output of 136 μJ, a power output of 155 mW and exerts a force of 66 mN.