Fig. 1. Wingtip motion for a Clione antarctica during a single wingbeat cycle (a–i) from lateral (above) and dorsal (below) perspectives. Mean relative velocity of the body (blue arrows) and mean body acceleration vectors (red arrows) are averaged from data for eight individuals. The external coordinate system is shown indicating the x-, y- and z-axes. The body coordinate system is indicated by the y'- and z'-axes, but, in this example, the x'-axis is not shown because it is coincident with the x-axis. The origin of the body coordinate system is at the near wing base.