Winging it with the history of flight
When the Wright brothers took to the air in late 1903, they made their first stuttering flights in a biplane, while 400 million years earlier, another set of aerial pioneers took a similar approach: insects. As we know from the fossilised imprints they left in rocks, insects closely related to today’s dragonflies, but with wingspans up to 75 centimetres, were the first creatures to conquer the skies. And they did it with a double set of wings.
Dragonflies and mayflies still use the four-wing design today, and they are very agile fliers. But as early aeroplane designers soon found, you only need one pair of wings to fly. As insects evolved, their second set of wings was adapted to other functions.
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“The best defence is a good offence”, the old sport and military adage goes. Beetles show that the opposite can also be true. In this order of insects, the front pair of wings evolved into hard, protective armour. As anyone who has watched a ladybird take off will know, when a beetle wants to fly, it swings its shell open to reveal a foldable set of wings. After landing, the wings are refolded and the armour reengaged.
Beetles have conquered the planet with this defensive play. There are more than 350,000 beetle species, more than any other form of life. More than a quarter of all species on the planet are beetles. No wonder Darwin was fascinated by them.
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Crickets and their close cousins the grasshoppers have converted their spare sets of wings into musical instruments. These are used mainly by the males to serenade members of the opposite sex, and the universal recognition of cricket song attests to their success.
Despite the similarity between cricket and grasshopper chirps, they play quite different instruments. Crickets, above, raise their front wings and rub the serrated edges together to create their song like a rasping percussion instrument.
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The grasshopper's song
Grasshoppers on the other hand, employ one of their long and very flexible rear legs as a bow, playing their front wings like a violin.
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The mystery of halteres
Two-winged flies, known as dipterans, seem at first glance to have lost their second set of wings altogether. But take a close look at the housefly, and you’ll see a tiny club-shaped structure where the rear wing would have been. It’s called a haltere. Other dipterans such as the crane fly, above, have more prominent halteres.
These halteres evolved from the wings. They are too small to provide useful lift yet they flap when the insect is airborne. They must provide some advantage for flies to put up with the weight of carrying them. So what are halteres for? (see Why are flies so hard to swat?)
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