Fig. 5. Sequence of wake structure during dorsal clap-and-fling maneuver when flapping one wing (upper rows, A–L) and flapping two wings (lower rows, M–X) generated by 2-D digital particle image velocimetry. The time values for each panel correspond to the time section before (negative values) or after (positive values) the clap occurs. Values in the images are fractions of the stroke cycle (0–1). (A,M) –350 ms (=0.94); (B,N) –200 ms (=0.97); (C,O) –50 ms(=0.99); (D,P) 0 ms (=1.00); (E,Q) +50 ms (=1.01); (F,R) +100 ms (=1.02); (G,S) +150 ms (=1.03); (H,T) +300 ms (=1.05); (I,U) +450 ms (=1.08); (J,V) +600 ms (=1.10); (K,W) +750 ms (=1.13); (L,X) +900 ms (=1.15). The wing section at the center of wing area is indicated by a white line. The leading edge of the dorsal wing surface is marked by a white half circle. Fluid flow velocities are plotted in color code and arrows correspond to velocity vector at each point in the fluid; longer arrows signify larger velocities.