PUB - Publikationen an der Universität Bielefeld

Unrestrained adult stick insects (Obrimus asperrimus) walked below a tread wheel 4 or 30 mm wide in the upside-down position or above a 'bridge' 30 or 60 cm wide in the upright position, They were recorded on video and the positions of reference points on the legs and on the body were measured on still frames, Step parameters such as step amplitude, step duration, swing duration, body height and ground width are given for broad and narrow footing as well as for leg trajectories and the course of leg joint angles, Joint angles were calculated directly between the leg segment vectors, Walking with a narrow footing, the stick insect used the same slow metachronal gait as on a broad footing, Adjustment to the narrow footing was accomplished by narrowing the ground base, raising the body distance, depressing the femora (by 40-45 degrees) and flexing the tibiae (20-25 degrees in the front and middle legs), The upper turning-point of the swing movement seems to be determined by a constant amplitude of the vertical movement component rather than a given position in a body-fixed coordinate system, Walking on a horizontal rod of circular cross-section, the insects preferred to walk upside down below the rod for small diameters, but preferred to walk upright above the rod if its diameter was great enough. (C) 1997 Elsevier Science Ltd.