Georges Louis Marie Félicien Jousset de Bellesme

“ The bird can change at will the angle of vibration of his wings, and therefore these organs serve to steer his flight. The insect is deprived of this power, because the angle of vibration, as a rule, is invariable in each species, the flying-muscles not being in the wings, but in that part of the thorax which supports the wings. ”

“ Suppress the balancers, and the flight becomes fatally downward, because the normal and invariable position of the center of gravity is in front of the axis of suspension; the animal, therefore, can not modify his movement in any way, the abdomen being but slightly movable, and the balancers cut off. If, now, we come to his relief and attach a tiny weight to his abdomen, just sufficient to carry the center of gravity back to its normal place, we restore to the insect the power to perform all his aërial evolutions. ”

“ The second pair of wings is transformed into organs having the special function of steering, the balancers or poisers; and these insects have accordingly a remarkable perfection of movement. A single pair of wings does all the flying, and, as they are not large, the diminution of the supporting surface is compensated by greater rapidity of vibration. ”