a, Three-dimensional reconstruction of a territorial interaction involving two male dragonflies. The reconstruction was achieved by using calibrated6 and synchronized (to within 10 μs) stereo cameras. Positions of the heads of the shadower (blue dots) and shadowee (red dots) are connected by lines at corresponding 20-ms steps. The connecting lines converge behind the shadower; the point of convergence indicates the apparent position of the shadower to the shadowee. The shaded sphere (radius, 11.3 mm) represents the uncertainty of the 'best' estimate of the intersection point. b, Angular-velocity profile produced by the shadowing dragonfly in the shadowee's eye (filled circles) compared with that produced by a virtual stationary object at the intersection point (hollow circles). c, Another example of motion camouflage. The connecting lines converge in front of the shadower during frames 1–8, after which the shadower begins to imitate an infinitely distant object. The radius of the intersection sphere is 8.5 mm.