VERTICAL TAKEOFF IN BIRDS AND INSECTS

The masters of vertical flight are the common housefly and the humming­bird. Both of them have remarkable flight control and are able to take off vertically and hover motionless in the air.

Most insects have two pairs of wings, but the housefly has only one pair—its hind wings have withered away to form two little stumps called halteres. The housefly flaps its wings about 200 times every second. Instead of flapping up and down, they make a figure-eight shape in the air. This directs air downward for takeoff. As the insect flies, the halteres vibrate. If the fly changes direction, the halteres’ vibration is disturbed, instantly giving the fly information about how it is moving. This helps the fly to control its flight with great precision.

Hummingbirds are the helicopters of the natural world. Most birds’ wings generate all of their lift on the down – stroke, but a hummingbird’s wings gen­erate lift on the upstroke, too. The bird’s body is tipped up so that its wings beat back and forth parallel to the ground. About three-fourths of the lift comes from the forward downstroke and the rest from the backward upstroke. To generate enough lift, the wings flap at up to eighty times a second.

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