The power coefficients for translation (CP,t) and rotation (CP,r) versus time during one cycle (midstroke angle of attack αm=35°, symmetrical rotation, non-dimensional duration of wing rotationΔτ r=0.36τc). τc, non-dimensional period of one flapping cycle; τ, non-dimensional time. The power coefficients for translation (CP,t) and rotation (CP,r) versus time during one cycle (midstroke angle of attack αm=35°, symmetrical rotation, non-dimensional duration of wing rotationΔτ r=0.36τc). τc, non-dimensional period of one flapping cycle; τ, non-dimensional time. Mao Sun, and Jian Tang J Exp Biol 2002;205:2413-2427 © The Company of Biologists Limited 2002