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Windsurfing insects have real direction

More than 1,500 years before Christopher Columbus and his crew sailed to the New World, Native Americans had already domesticated turkeys twice: first in south-central Mexico at around 800 B.C. and again in what is now the southwestern U.S. at about 200 B.C., according to a new study.
/ Source: Discovery Channel

As they migrate, butterflies and moths choose the winds they want to soar with, and they change their body positions if they start drifting in the wrong direction.

This new finding suggests that insects may employ some of the same strategies that birds use for traveling long distances. Scientists have long thought that insects were simply at the mercy of the prevailing breeze.

The insights might help farmers prepare for a global warming-induced onslaught of migrating pest insects, among other applications.

"Insects are so small that there was this feeling that maybe they were just being blown about by the wind, whereas our study shows that's not the case," said Jane Hill, an entomologist at the University of York in the United Kingdom and co-author of the research appearing in this week's issue of Science. "They go with the wind, but they choose which winds to go with."

Each spring and fall, millions of insects make treks that can cover hundreds or even thousands of miles. Monarch butterflies, which travel from Canada to Mexico, are perhaps the most famous example. A variety of locusts, moths, dragonflies and beetles migrate, too.

As fascinating as their feats of flight are, migrating behavior has been difficult to study in insects because many long distant trips happen thousands of feet above ground. Only recently have scientists developed technologies that can detect such little creatures at such great heights.

Hill and colleagues used two vertical-pointing radar devices in southern England to look at more than 100,000 moths and butterflies during their seasonal migrations. From the data, which spanned several years, the researchers were able to see which types of insects flew by, what direction they were facing, and how high up they were, among other details.

As expected, results showed that both night-flying moths and day-traveling butterflies headed north in spring — to the U.K. from northern Africa and the Mediterranean. Come autumn, they returned south again.

To the researchers' surprise, though, the insects weren't passive hitchhikers on the prevailing winds. In autumn, for example, most gusts blew from the east, but the insects somehow sought out breezes that carried them south and they positioned themselves to navigate directly to their wintering homes.

Even in the spring, when most winds flowed northward, the insects didn't always go with the flow. If breezes weren't blowing in the exact direction they wanted to go, the insects altered their body positions to compensate. Many migrating birds do the same thing.

Unlike particles of dust, the study also found, butterflies and moths actively flew within the air streams that pushed them along. By adding flight speeds to wind speeds, the scientists calculated that butterflies and moths can travel as fast as 100 kilometers an hour (62 mph).

At that rate, these delicate little creatures could make the 2,000-km (1,243-mile) trek from Africa to the U.K. in just three or four nights. With a computer model, the scientists further estimated that this windsurfing strategy allows the insects to travel about 40 percent further than a drifting particle could.

Biologist Lincoln Brower has been studying and marveling at the migration of monarch butterflies for 55 years. To him, the new paper hammers home how astounding it is that generations of miniature-brained insects can travel such long distances and find their way, again and again.

"It is an incredibly complicated system that these tiny insects have," he said. "Somehow they know where they are, and they know where they are going. Using the wind makes it all possible."

The findings may have real-world applications. With climate warming, Hill said, migrating insects are growing in number, including varieties that infest agricultural fields. Knowing how and when these pests move could help when farmers decide when to spray their crops.

Eventually, Brower added, scientists might be able to build miniature robots that could orient themselves in space with the grace and ease of a butterfly.