Slashdot Mirror
Camouflage in Motion
Adrian writes "Remember Jurassic Park, where Goldbloom stood really still and the T-Rex couldn't see him? Well, there might be a better way. Scientists have found that dragonflies can dissappear by keeping their image on your retina in the same place, even if you move. How they manage it still has them puzzled... ;)"
I've never seen a puzzled dragonfly. Oh. The scientists.
I'd assume that the dragonfly merely tries to keep the thing it's hiding from in the same position on *its* retina. It'd be a fairly simple feedback mechanism, if you did it with analogue electronics.
-Yarn - Rio Karma: Excellent
King Charles 'beheaded' guests who bored or annoyed him by viewing them at such an angle that his blindspot was over their head. Try it for yourself
Well duh. Didn't they ever catch flies when they were young? The way to do it is to take two fingers and follow the fly with them, maintaining the distance between your hand and the fly. after a while the fly will think your fingers are part of the background and will easily let you catch it.
I've seen something like this before. Once I was outside cleaning up after a party. I went to pick up a vase of flowers and I noticed a few tiny fruit flies(?) that were hovering near the flowers. The funny thing was that when I picked up the flowers, these flies would maintain the exact same relative position to the flowers. Even if I rotated the vase around its axis.
It was like taking the flies for a walk on an imaginary but invisible leash.
I guess that the flies had an instinct that to remain still, they must reduce the error in *their* retina between the current background image and the stored background image. I am guessing that dragonflies have evolved to do the same thing but with a greater degree of freedom. i.e. a chosen target rather than the whole background.