Fig. 9. (A) Effect of body acceleration on the critical punting speed to overturn a crab in still water. Means of mean measurements for five crabs were used to calculate critical punting speed. Filled symbols and solid lines represent a crab in the aquatic posture. Open symbols and dashed lines represent a crab in the terrestrial posture. Angles of attack were –4° (circles), 0° (squares) and +4° (triangles), respectively. (B) Effect of water acceleration on the critical ambient water velocity necessary to wash away a crab standing with an angle of attack of 0°. Calculations assumed that crabs grasped the substratum with maximum horizontal tenacity (13N). Means of mean measurements for five crabs were used to calculate critical water velocities. Filled symbols indicate a crab using the aquatic posture. Open symbols represent a crab using the terrestrial posture in water.