Fig. 1. `Clap and fling' (redrawn from Weis-Fogh, 1973). The three-dimensional motion (top) and the corresponding two-dimensional approximation (bottom). In this drawing, the insect flies with its body oriented almost vertically, and the wings move in a horizontal plane. At the beginning of the upstroke (A), the wings move from the ventral to the dorsal side of the body, and rotate together about the leading edges. At the beginning of the downstroke (B), the wings rotate apart about the trailing edges. Towards the end of rotation, the wings translate away from each other.