Fig. 5. Simultaneous kinematic and hydrodynamic events during the first three half-strokes of a pupal mini-dive. Data points plot the motion of the centre of gravity (filled circles), the abdominal paddles (open circles) and the dye front moving along with the associated vortices (V1–V3) (open triangles, filled squares and filled triangles, respectively) at 20ms intervals. The data are from four individual dives, and the cartoon shows the starting orientation in each case (0ms position). Arrows show the directions of movement of the dye front along the propagation axis of the vortex and of the centre of gravity and abdominal paddles.