If there is a strong headwind, its forward speed will be reduced. Thus its optic flow regulator will constantly force it to reduce altitude so that the optic flow always remains at the reference value. The insect has to make a forced landing against the wind, but a safe landing, because it takes place at a vertical speed of zero. Reactions of this type to a headwind have been described countless times in insects and even in birds. They are also observed on the microhelicopter each time it faces a laboratory-produced headwind, reinforcing the hypothesis that flying creatures have an optic flow regulator.
The very simple control scheme proposed takes into account 70 years of often surprising observations of the behavior of winged insects. It accounts for the fact not only that insects descend facing a headwind and ascend with a tailwind, but also that honeybees land with a constant slope and drown when crossing mirror-smooth water1.
Behind this astonishing behavior, hidden in the insect's cockpit, are movement detector neurons that act as optic flow sensors. The team patiently decoded the functioning of these neurons using ultra-fine microelectrodes (with a diameter of a thousandth of a millimeter) and a specially designed microscope. They then produced an electronic microcircuit based on this principle. The most recent version weighs only 0.2 grams. This is the neuron that does most of the work on board the microhelicopter.
The optic flow regulator helps explain how an insect manages to fly, even in unfavorable wind conditions, without measuring its ground height, groundspeed or descent speed, in other words without using any of the usual aircraft onboard flight aids like radar, GPS, radio-altimeters and variometers. An insect brain wouldn't cope with these cumbersome, heavy, energy-consuming devices.
This important work shows that this new science called biorobotics, that the team from Marseille star