Meeting Abstract

P2-154   -   Biomechanics of insect locomotion on inclined and inverted surfaces Beck, H/K*; Labonte, D; Imperial College London; Imperial College London h.beck20@imperial.ac.uk

Insects navigate various inclines effortlessly in order to find food, escape from predators, or predate. Climbing on slopes brings with it two biomechanical challenges, associated with the change of the orientation of the gravitational force vector relative to the surface normal: On inclines between 0-90° with respect to the horizontal, insects transition from a mechanical scenario where all feet are passively pressed onto the surface to a scenario where some feet need to generate adhesive forces to avoid toppling. Between 90 – 180°, in turn, a second transition occurs at the end of which all contact points are pulled away from the surface, and thus need to form stable adhesive contacts. How do these biomechanical transitions influence gait patterns? In order to answer this question, we filmed stick insects (Sungaya inexpectata) climbing on slopes with inclinations varying between 0-180° using five cameras. We tracked 46 key locations using markerless pose estimation (DeeplabCut) and reconstructed locomotor patterns in 3D. Insects dominantly used a tripod gait for surface inclinations <90° and countered the risk of toppling by lowering the height of their centre of mass as the inclination angle increased. However, for inclination angles >40°, most insects needed to generate adhesive forces for the majority of the stance phase in order to remain dynamically stable. As insects transitioned from vertical to inverted surfaces, the minimum number of legs in ground contact increased from three to four. This „inverted stability rule“ enables insects to move at least one limb without the risk of dramatic failure due to moments about contact points or unbalanced frictional forces. By improving our understanding of how climbing insects deal with the mechanical challenges arising from climbing varying inclines, we aim to enhance the mobility of six-legged robots.