How Insects Fly

How Insects Fly Insect flight remained something of a mystery to scientists until recently. The small size of insects, coupled with their high wing-beat frequency, made it nearly impossible for scientists to observe the mechanics of flight. The invention of high-speed film allowed scientists to record insects in flight, and watch their movements at super slow speeds. Such technology captures the action in millisecond snapshots, with film speeds of up to 22,000 frames per second. So what have we learned about how insects fly, thanks to this new technology? We now know that insect flight involves one of two possible modes of action: a direct flight mechanism, or an indirect flight mechanism. Insect Flight Through a Direct Flight Mechanism Some insects achieve flight through a direct action of a muscle on each wing. One set of flight muscles attaches just inside the base of the wing, and the other set attaches slightly outside the wing base. When the first set of flight muscles contracts, the wing moves upward. The second set of flight muscles produces the downward stroke of the wing. The two sets of flight muscles work in tandem, alternating contractions to move the wings up and down, up and down. Generally, the more primitive insects like dragonflies and roaches use this direct action to fly. Insect Flight Through an Indirect Flight Mechanism In the majority of insects, flying is a bit more complex. Instead of moving the wings directly, the flight muscles distort the shape of the thorax, which, in turn, causes the wings to move. When muscles attached to the dorsal surface of the thorax contract, they pull down on the tergum. As the tergum moves, it draws the wing bases down, and the wings, in turn, lift up. Another set of muscles, which runs horizontally from the front to the back of the thorax, then contract. The thorax again changes shape, the tergum rises, and the wings are drawn down. This flight method requires less energy than the direct action mechanism, as the elasticity of the thorax returns it to its natural shape when the muscles relax. Insect Wing Movement In most insects, the forewings and hindwings work in tandem. During flight, the front and rear wings remain locked together, and both move up and down at the same time. In some insect orders, most notably the Odonata, the wings move independently during flight. As the forewing lifts, the hindwing lowers. Insect flight requires more than a simple up and down motion of the wings. The wings also move forward and back, and rotate so the leading or trailing edge of the wing is pitched up or down. These complex movements help the insect achieve lift, reduce drag, and perform acrobatic maneuvers.