Jumping behaviour in a Gondwanan relict insect (Hemiptera: Coleorrhyncha:Peloridiidae)

Abstract

SUMMARYJumping by a relict insect, Hackeriella veitchi (Hacker 1932),belonging to the ancient Coleorrhynchan line that diverged from other Hemiptera in the late Permian, was analysed from high-speed images captured at rates of 2000 s–1 and from its anatomy. This 3 mm long,flightless insect weighs up to 1.4 mg and can jump by rapid movements of the hind legs that accelerate the body in 1.5 ms to a take-off velocity of 1.5 m s–1. This performance requires an energy expenditure of 1.1μJ and a power output 0.74 mW, and exerts a force of 1.24 mN. It achieves this with a body design that shows few specialisations for jumping compared with those of other groups of Hemipterans such as the froghoppers or leafhoppers. The hind legs are only 10% longer than the front and middle legs by virtue of longer tibiae and tarsi, and are only 65% the length of the body. The main thrust for a jump is provided by the rapid rotation of the fused trochanter and femur about the coxa of a hind leg, in a movement that forces the hind tarsus against the ground and raises the body to take off. In some jumps the two hind legs move together, but in others the movements may not be closely synchronised, thereby imparting a rotation on the body that is maintained once airborne. When the time difference is larger, the rapid movement of just one hind leg results in the insect falling from its perch in an adaptive escape response.