Why is the common housefly able to perform complex and precise aerobatic maneuvers? When hit by a gust of wind, why can the insect quickly right itself and maintain its course? The answer involves, in part, two tiny appendages called halteres, one located behind each wing. *

Consider: A haltere is like a tiny drumstick with a knob on the end. During flight, the halteres swing up and down at the same frequency as the wings but in the opposite direction. Scientists have discovered that halteres serve as an ingenious type of gyroscope, helping flies to remain stable during flight. *

With their clubbed ends, halteres “beat in one particular direction, like the pendulum of a clock,” says the Encyclopedia of Adaptations in the Natural World. If, during flight, a fly abruptly turns, whether intentionally or because of a sudden gust of wind, “the stem of the haltere will twist,” states the encyclopedia. “This twisting is detected by a dense cluster of nerve endings attached to the haltere, and the information is fed to the brain so the fly can take the appropriate action to stay . . . on course.” As a result, flies are highly agile and hard to catch.

Engineers see countless applications of haltere-inspired technology in such things as robots, micromechanical flying insects, and space vehicles. “Who would have thought a small, unlovely creature like the fly could teach us so much?” wrote aerospace researcher Rafal Zbikowski.

What do you think? Did the gyroscopic haltere of the fly come about by evolution? Or was it designed?