Shadowee's Retina with That Produced by Electromagnetic Waves

a virtual, stationary object positioned at the estimated intersection point (Fig. 1b). The two angular-velocity profiles are very similar, indicating that the strategy is likely to be effective in concealing the motion of the shadower. In other male–male interactions, we observed variations in motion camouflage (Fig. 1c). During the first eight frames of filming, the lines connecting the two insects intersect at a small region between them; the shadower is therefore emulating a fixed object in front of it. Here the shadowing animal is not flying towards the shadowee, but is moving in the opposite direction. This is evidence that the flight pattern of the shadower is motivated by motion camouflage and is not an artefact or by-product of chasing per se . After frame nine, the intersection point shifts to infinity — that is, the shadower imitates an object at infinity. This example reveals that a shadower can combine two different types of motion camouflage in a single episode. Active motion camouflage requires the shadower to move in such a way that it imitates the trajectory of a fixed object on the retina of the shadowee by precise flight control and positional sensing, although exactly how the shadower achieves this is unclear. Given the high sensitivity of the insect visual system to movement, motion camouflage is likely to be the key to the success of such manoeuvres. Akiko Mizutani*, Javaan S. Chahl*†, Mandyam V. Srinivasan* *Centre for Visual Science, Research School of Biological Sciences, Australian National University, PO Box 475, Canberra, ACT 2601, Australia e-mail: [email protected] †Weapons Systems Division, Defence Science and Technology Organisation, Edinburgh, South Australia 5111, Australia