When they fly, insects use their vision for piloting, just like human pilots. The electric signals from their facetted eyes travel through specialized neurons to stimulate the wing muscles, which let the insects correct their flight and avoid crashes. Could these same neurons be used in a sort of "automatic pilot"? This is what Nicolas Franceschini, Franck Ruffier and Julien Serres have just shown. These biorobotics specialists from the Movement and Perception Laboratory (CNRS/Universit de la Mditerrane) in Marseille, France have revealed an automatic mechanism called the "optic flow regulator" that controls the lift force. The researchers obtained these results by modeling the overland flight navigation of insects using experiments carried out on OCTAVE, a captive flying robot microhelicopter that can reproduce much of the mysterious natural insect behavior. Their work is published online in Current Biology, February 8, 2007.
How does a tiny creature like a fly or a bee, with a brain the size of a pinhead, manage to make such a magnificent job of controlling its flight, and avoid crashing to the ground? Today it is known that the sensory motor prowess of these flying miniatures depends on the nervous system, made up of between one hundred thousand and one million neurons. When an insect, bird or pilot flies over land, the image of the ground below sweeps from front to back across the central part of the visual field, creating an "optic flow", which is defined as the angular speed at which the ground contrasts move past. By definition, this angular speed is equal to the ratio of the horizontal speed and the altitude. What these authors call an "optic flow regulator" is a reflex that keeps the optic flow, and thus the speed/altitude ratio, at a constant value. If the insect changes speed, this reflex will make it change altitude so that ratio remains constant. Adjusting the speed/altitude ratio means that the insect has no need to measure either its s
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