Sequence of movements by the maxilliped flagella. A power stroke is indicated by the thick black bars and the return stroke (adduction) by coloured boxes (following the same colour coding as in Figures 1 and 2) and intervening periods of inactivity are represented by the thin black lines. (A) Crab, Carcinus. The maxillipeds on one side move with the power strokes occurring in the sequence 3, 2 and 1. In the example shown, the frequency of movements was 10 Hz and thus lower than average for a crab. (B) Crayfish. The maxillipeds move at the same time on both sides, with the power strokes on each side following the sequence 3, 2 and 1. The power stroke in maxilliped 3 on the right side precedes that of left maxilliped 3.