Bees Wearing Reflectors Help Scientists Track Insects' Training Flights

Studying how bees do this has long stymied researchers, because bees fly too far and too fast to watch with the naked eye, and they are too small to wear energy-emitting devices required for radio tracking. But a newly developed radar system, in which bees wear ultra-light reflectors, allowed researchers of the University of Illinois and the University of Greenwich and the Rothamsted Institute in the United Kingdom to track the bees. Their findings appear in the Feb. 3 issue of the journal Nature.

As bees take training flights, they cover an increasingly larger area around their hive. They appear to achieve this greater reconnaissance not by taking longer flights, but by flying faster and faster, the scientists report.

Honeybees live in a social world known for its distinct division of labor based on age-specific tasks. They begin their adult life working inside the hive as sanitation workers and nursemaids, among other roles. They then shift to foraging outside the hive when they're about 3 weeks old.

"Imagine living in the confines of a dark castle for about half your adult life and then having to venture outside into a world full of sunshine to find food to bring home," said Beth Capaldi, lead author and a postdoctoral researcher at the U. of I. "That would be a huge change in your sensory environment, and it would probably take time for you to adjust. That's how it is for the bees."

Capaldi's U. of I. colleagues on the study were Susan Fahrbach and Gene Robinson, professors in the entomology department and neuroscience program.

The scientists were interested in what orientation flights might tell them about how bees learn to navigate -- a highly demanding ability for a creature with a brain the size of a grass seed. The researchers used harmonic radar, a technology developed in 1996 by the Greenwich group to allow individual insects to be tracked in flight. Each bee wears a tiny tag that re-emits a unique harmonic of a particular radio frequency. When the bee flies, the signal can be discriminated from background radar reflections because only the tagged bee responds with the frequency being broadcast in a field.

The findings suggest that orientation flights allow bees in a progressive way to visit different positions and view different, and larger, portions of the landscape around the hive.

The scientists now want to know why -- aviation skill perhaps -- some bees take as few as one while others take up to 17 orientation flights prior to becoming a forager. They also are interested in what happens to the brain during orientation flights.

Among the multiple funding sources for the study were the National Science Foundation, National Institutes of Health, and the Biological Sciences Research Council in the United Kingdom.