Learning How Insects Fly

In 1930, scientists at Gottingen University, Germany, tried to figure out how a bumblebee could actually fly. When they analyzed their studies and
calculations, these experts concluded that—from a scientific point of view—the bumblebee should not actually be capa­ble of flight. It was not the right shape. More recently, scientists have used robot insects to study the mechanics of insect flight. They created large-scale model insect wings, stuck them in a tank of thick oil, and used a motor to beat the wings up and down. Flapping slowly in the oil, the model wings acted much as tiny wings do when they are flapping very fast in the air.

Such experiments have shown that an insect can use three kinds of wing movements to perform amazing maneu­vers. When a fly is trying to dodge a predator, such as a human trying to swat it, the insect can change direction in thirty-thousandths of a second.

Three Maneuvers

The first movement, unique to insects, is known as delayed stall, which means that the insect wing sweeps forward at a high angle. The insect wing cuts through the air at a steeper angle than an air­plane wing. An airplane at this stage would stall, losing lift and increasing drag, and it would most likely crash. In an insect, however, the steep angle pro­duces a vortex (like a whirlpool in the air) above the wing, cre­ating extra lift.

The second insect technique is rotation­al circulation. Toward the end of its stroke,

О A swarm of locusts surrounds a farmer in the Philippines. Locusts can destroy entire crops of rice and sugar.

О The mosquito belongs to the same insect family as a housefly. Instead of rear wings, mosquitoes and flies have two halteres to help them fly.

the insect wing rotates backward. This produces backspin, which in turn pro­duces extra lift.

The third insect trick is wake capture, which gains extra lift by recapturing energy lost in the wake (the disturbed air left behind the flying insect). As the wing moves through the air, it creates turbulent air behind it. By rotating the wing before starting the return stroke, the insect captures some of this air, and the energy within it, for extra lift.

Acrobatic insects, such as the hover – fly, make use of rotational circulation and wake capture but do not often use delayed stall. Butterflies do not appear
to use any of these three techniques very much. They fly more like birds, gliding or flapping their wings in a less complex fashion. Flies have a pair of special balance organs instead of rear wings. Called halteres, they are shaped some­what like tiny clubs. These organs help give flies their remarkable flying skills.