Peripheral Influences On the Movement of the Legs in A Walking Insect Carausius Morosus

Anterior extreme position (AEP) and posterior extreme position (PEP) of the legs of stick insects were measured during walking on a treadwheel or on a slippery glass plate. In several experiments, either protraction or retraction of a middle or hind leg was interrupted. The AEP of other legs was independent of a protraction interruption but PEP was displaced backward in the leg anterior to the interrupted leg. When a leg was standing on a fixed platform (interruption of retraction) no changes were found in AEP and PEP for the other legs but if the platform was slowly moved, PEP of leg on the platform was moved forward. These results disagree with several published hypotheses. The results suggest the hypothesis of a position-dependent threshold value for protraction which is modulated by co-ordinating influences from other legs.