Supplementary information: legends for the supplementary figures and video sequence.
This disc contains Adobe Illustrator 8 , PDF and Photoshop versions of each of the4 supplementary figures. It also contains a Quicktime video sequence. These are for publication on the Nature web site as supplementary information. The figure legends for these items follow:
Quicktime video sequence 5van11a.mov This sequence shows the 434g male taking off from the golf tee in the windtunnel in a flow of 1.5m/s from left to right. The first wingbeat shows a clap and peel, the clap produces a vortex ring that moves away to the right at a speed higher than the free-stream flow velocity indicating the generation of thrust (and some downforce). The wingtip vortices are fully formed from the beginning of the downstroke, providing no evidence of any Wagner effect delay in generation of circulation. There is no wake capture or evidence of rotational mechanisms at the end of the first downstroke. The first upstroke retains the leading edge vortex, and the patterns of flow around the wing and position of the stagnation point on the undersurface indicate that the upstroke is lifting. Rotational mechanisms are evident at the end of the second downstroke, the position of the stagnation point shifts aft during wing rotation indicating increasing circulation on the wing. The discrete stopping vortex shed at the bottom of the second downstroke indicates that there has been no significant wake capture during this stroke. At the end of the third downstroke the wing is rapidly swept aft so that on the subsequent upstroke it passes through the stopping vortex shed from the third downstroke, disrupting the structure of the stopping vortex and leaving a large area of fluid in slow disordered motion where the tight circulation of the stopping vortex should be. The last upstroke in the sequence sheds a particularly strongly marked wingtip vortex indicating that this upstroke was negatively loaded generating thrust and downforce.
Supplementary Figure 1: Images of the flow over the wings at successive positions along the span. These images are taken from multiple cameras at different orientations and provide a composite representative image of the structure, size and shape of the leading edge vortex at different spanwise positions along the wing.
a)the arrow points to smoke streams spiraling around the wingtip vortex just outboard of the wingtip.
b) the arrowed smoke streams cross the wingtip and then enter the wingtip vortex. The leading edge vortex is continuous with the wingtip vortex.
c)The arrow shows where a smoke stream that has passed above the leading edge vortex reattaches on the wing surface.
d)As in (c) the arrow points to a smoke stream marking the reattachment point. The leading edge vortex is the same size or larger here, halfway along the wing, than it is closer to the tip. The leading edge vortex is not conical, none of the images show spanwise flow.
Supplementary Figure 2 Successive frames showing wing rotation at the end of a downstroke. The arrows in (a) and (d) point to the edge of the wingtip vortex. As the wing rotates the wingtip vortex increases in diameter indicating that circulation has been generated by the rotation of the wing even though the translation phase of the downstroke has finished. The stagnation point (where a smoke stream hits the underside of the wing) moves backwards along the wing during the image-sequence also indicating an increase in circulation due to the wing rotation.
Supplementary Figure 3 Clap and fling (peel). The discrete vortex ring produced by the clap is visible behind the insect (arrowed). The wingtip vortices (arrowed) are fully formed as soon as the wings separate indicating that the peel has generated circulation without any delay at the start of the wingbeat. There is no evidence of any Wagner effect. This is a take-off wingbeat selected because the clap and peel vortex is formed here in an area of clear smooth flow undisturbed by any previous wing strokes.
Supplementary Figure 4. Successive images during a wake-capture wingbeat. The arrows in images b) and c) point at the wingtip. Between these two successive images the wingtip has been swept backwards relative to the body (and has closed up with the hindwing). This drops the wing backwards and downwards so that its path on the upstroke intercepts the stopping vortex which is disrupted and forms the large area of disorganized smoke visible at the lower right of image d).