Jumping and take-off in a winged scorpion fly (Mecoptera, Panorpa communis).

Abstract

High-speed videos were used to analyse whether and how adults of a winged species of scorpion fly (Mecoptera, Panorpa communis) jump and determine whether they use the same mechanism as that of the only other mecopteran known to jump, the wingless snow flea, Boreus hyemalis Adult females are longer and heavier than males and have longer legs, but of the same relative proportions. The middle legs are 20% longer and the hind legs 60% longer than the front legs. A jump starts with the middle and hind legs in variable positions, but together, by depressing their coxo-trochanteral and extending their femoro-tibial joints, they accelerate the body in 16-19 ms to mean take-off velocities of 0.7-0.8 m s-1; performances in males and females were not significantly different. Depression of the wings accompanies these leg movements, but clipping them does not affect jump performance. Smooth transition to flapping flight occurs once airborne with little loss of energy to body rotation. Ninety percent of the jumps analysed occurred without an observable stimulus; the remaining 10% were in response to a mechanical touch. The performance of these jumps was not significantly different. In its fastest jumps, a scorpion fly experiences an acceleration of 10g , expends 23 µJ of energy and requires a power output less than 250 W kg-1 of muscle that can be met by direct muscle contractions without invoking an indirect power amplification mechanism. The jumping mechanism is like that of snow fleas.