Radar reveals secrets of bumble bee's flight

THE MYSTERY of how bumble bees find their way home in strong winds may have been solved with the help of radar.

Entomologists have long wondered how bees - renowned for their homing instincts - navigate in cross-winds without being blown off course.

Scientists have discovered that bees are able to take wind speed and direction into account when using the position of the Sun as a compass for navigating to and from their hives. Rather than using mathematics to calculate wind speed and direction, like aircraft pilots, bees monitor how much they are being blown off course by looking at the ground and constantly adjusting their line of sight to compensate, scientists have found.

In research published in the journal Nature, Joe Riley, professor of radar entomology at the University of Greenwich, fitted bumble bees with tinytransponders, which allowed him to track their precise movements with radar.

Professor Riley found that bees monitored during journeys of up to one kilometre have a keen sense of how much the wind is blowing them off course and appear to alter their flight direction to make amends.

"If bees flew straight toward their target on a windy day they would drift downwind. We've shown that the bees can make allowances for this," Prof esssor Riley said. "Human pilots need to know windspeed and direction and it's quite a complicated process. Bees do it differently. They know the true compass direction from the direction of the Sun and they look down on the ground to see how it moves underneath them."

If they are being blown off course the bees adjust the direction their heads are facing so that the ground begins to move in the direction they want to go, he explained.

Scientists also found that, on windy days, bees travelling against the prevailing wind fly lower than usual to avoid the faster windspeeds at higher altitudes. Bees travelling downwind, however, take advantage by flying higher to save energy.

The scientists found that the bees have an average flight speed of about seven metres a second, which is faster than previous estimates for the fastest flight of a bumble bee.