Jumping in a winged stick insect

Abstract

SUMMARYThe Thailand winged stick insect (Sipyloidea sp.) flees rapidly from a disturbance by jumping forwards when stimulated on the abdomen and backwards when stimulated on the head. The mechanisms underlying these fast movements were analysed by measuring movements of the body and legs from images captured at 250 Hz.A forward jump of both adults and nymphs involves movements of the abdomen and the middle and hind pairs of legs. The abdomen is raised and swung forwards by flexion at the joint with the metathorax and at the joint between the meso- and metathorax. At the same time, the tibiae of the hind and middle legs are extended and their femora depressed. The femoro-tibial joints of the legs are not fully flexed before a jump, and no structures in these joints appear to store muscular energy. The whole jumping sequence takes approximately 100 ms and results in take-off angles of 10-35° at velocities of 0.6-0.8 m s-1 and with an acceleration of 10 m s-2. The abdominal angular velocity was 2000° s-1and the tip of the abdomen moved at linear velocities of some 1 m s-1, while the maximum rate of tibial extension was 4000°s-1.Rapid backward movements result either in the collapse of the body onto the ground, with a displacement away from the stimulus of approximately half a body length, or in the propulsion of the insect off its perch. Neither movement involves curling of the abdomen.From a horizontal posture, the forward jumps result in a displacement of a few body lengths. More lift can be generated in adults by elevating the hind wings as the abdomen is swung forwards and depressing them as the legs lose contact with the ground. In this way, jumps can lead directly to flapping flight. Take-off into flight can, however, be achieved without the abdominal movements seen during jumping.From a vertical posture, a forward jump propels the insect upwards and backwards before it falls to the ground horizontally displaced from its perch. Backward movements result in the insect falling with little horizontal displacement from its perch.

Surface roughness, claw size and leg elasticity influences on the jumping of Acheta domesticus crickets

“…All analyses of the kinematics are based on the two-dimensional images provided by a single camera. This experimental approach is coherent with recently published papers [9,11]. Sequential images of 10 jumps from each of the 3 substrata by 3 adults of either sex were captured with a DCR SR55E SONY digital video camera.…”

“…This terrestrial locomotor skill requires the coactivation of limbs, skeleton and contractile elements of the muscles which provide additional power required to accelerate or decelerate during locomotion performances [5]. Referring to insects, some of them have evolved long hind legs and use direct muscle contractions to move long levers, while other with short legs have developed catapult mechanisms that store elastic strain energy and then release it suddenly to power the jump [2,[5][6][7][8][9][10][11][12]. It is well known that a jumping cycle consists mainly of four sub-phases (propulsion, flight, landing and recovery) and all these phases must be of short duration with large displacements of the centre of mass to ensure optimal and rapid escape, so long horizontal jumping distance and high takeoff velocity [13].…”