Passive limb behavior in S. polymorpha and S. sexspinosus. Passive limb behavior observed in S. polymorpha on (A) less rugose (Rg = 0:17) and (B) more rugose (Rg = 0:44) terrain. Passive limb behavior observed in S. sexspinosus on (A) less rugose (Rg = 0:17) and (B) more rugose (Rg = 0:44) terrain. All videos playback at 0.1x speed.