Leg movements of stick insects walking with five legs on a treadwheel and with one leg on a motor-driven belt. I. General results and 1:1-coordination.

Five legs of a fixed stick insect walked on a double treadwheel. The left hindleg (L3) walked on a motor-driven belt. When the belt was slower than the wheels L3 made less steps than the other legs and when the belt was faster than the wheels it made more steps than the other legs. In the case of slowlier stepping of the "belt-leg", the motor neurons of the retractor coxae muscle of this leg showed a high activity when the leg was pulled backwards by the belt. This activity was modulated in the step rhythm of the "wheel-legs". When all legs showed the same stepping frequency (1:1-coordination) the protraction duration of L3 was almost independent of step-period, as well as the lag between onset of protraction of L3 and that of L2. In some cases only L3 could be made to step on the belt even when all other legs did not walk.