苍蝇只用一对前翅飞行，后一对翅膀已退化成为一对哑铃状的“平衡棒”，这一对小棒，能使它飞行时保持身体平衡和纠正航向。苍蝇飞行时，平衡棒以每秒３００次的频率振动。如果身体发生倾斜和偏离航向，振动平面发生变化时，平衡棒的基部感受器就会感觉到，并传递给大脑神经中 The fly uses only one pair of front wings for flight, while the pair of wings have degenerated into a pair of dumbbell-shaped “balance sticks” that allow it to maintain its balance and correct heading while flying. When flies fly, the balance bar vibrates at 300 times per second. If the body is tilted and deflected, when the vibration plane changes, the base of the balance bar will feel and transmit to the brain