Developments in Brief : Research Takes Flight--and Now Two Scientists May Know Why Insects Did

Using a wind tunnel, heat sensors and epoxy models of prehistoric insects, two researchers say they have learned why insects developed wings hundreds of millions of years ago.

The answer, according to Joel Kingsolver of Brown University and Mimi Koehl of the University of California, Berkeley: Tiny winglets made excellent solar panels, allowing ancient insects to capture extra warmth from the sun, increase their body temperature and move faster in cooler weather. As the wings got longer, the insects’ ability to capture heat improved. Eventually, the wings became sufficiently long that flight became possible.

The question of wing development has puzzled biologists since the development of the theory of evolution, which held that winglets must have served a purpose or they would not have evolved into wings. The first fossils showing winged insects date about 350 million years ago, long before the evolution of birds.

“Our results show that when you go from no wings to little wings, there is no aerodynamic advantage,” Kingsolver said. “But once you reach that certain minimum wing size, then flight can take over.”

In the past, biologists had suspected that winglets might have been used for gliding, but that theory fell apart when Kingsolver and Koehl took their insect models into the wind tunnel.

It is also possible that winglets might have been used by insects to attract mates. But “the only way to see that would be through a time machine,” Kingsolver said.