Figure 9.

Morphological basis of twist and camber generation. The figure shows the forewing and hindwing of locust L4 at the (a) early and (b) late downstroke (t̂=0.2 and 0.4, respectively). The green wisps at the wing tips show the immediate time history of the wing-tip position to convey a sense of the wing's motion. Nine local aerofoil sections are shown to illustrate the camber distribution. The chordwise mesh elements for each section are coloured according to their own local angle of incidence to illustrate the twist distribution. Early in the downstroke (a), the positive camber of the hindwing results from the negative incidence of its remigium (figure 10) relative to the rest of the hindwing. Similarly, the positive camber of the forewing early in the downstroke results from the negative incidence of the anterior panel of its remigium relative to the rest of the forewing. Late in the downstroke (b), the positive camber of the hindwing is increased by the umbrella effect operating in the vannus (figure 10; see the text for discussion). The positive camber of the forewing is sharply increased at this stage of the stroke by the rotation of the clavus (figure 10).