The Locomotion of the Cockroach Periplaneta Americana

ABSTRACT The locomotion of free, intact cockroaches, Periplaneta americana, was studied with the aid of high speed motion pictures. The insects used a single gait, alternating triangle, at all speeds of locomotion (5–80 cm/s) except the very lowest ones (below 5 cm/s). Both forward (protraction) and rearward (retraction) movements of the legs relative to the body decreased in duration as the insect’s rate of forward progression increased, but at different rates. In addition, protraction was usually shorter for the two middle legs than for the remaining four. The ratio of protraction to retraction increased as the locomotor rate increased. The rate of change of this ratio was the same for each of the legs. Phase relationships between adjacent ipsilateral legs were constant at about 0·5 at all walking speeds above about 5 cm/s. Phase between legs in a single segment (i.e. contralateral pairs) was constant at about 0·5 at all speeds. The locomotion of Periplaneta was compared to that of other insects. Despite the differences, a single mechanism could account for walking in each.