Mini-radar keeps tabs on flight of the bumblebee

British scientists have invented the world's smallest radar transponder capable of tracking the low-level flight of insects.

The researchers have proved their device - which weighs just 3mg and measures 16mm - works by supergluing it to bees as they leave the hive. And they now hope to refine the technology to help scientists fight disease spread by the tsetse fly in Africa.

The fly is a plague pest that attacks humans and cattle with often fatal results. Control in the past has been managed by spraying insecticide over vast areas of land, but the need for increasing environmental sensitivity means that a better method has to be found.

Dr Joe Riley leading the research team at the Natural Resources Institute radar unit at North Site, Malvern, said: "Hopefully, the research we are doing with the bees will help us develop a similar device to track the tsetse fly. Scientists in Zimbabwe, who have been looking at the insects' habits for the past 20 years, need to know how they fly when they are close to the ground. Ordinary radar is no use because of reflections from trees and shrubs. We've used bees as a flying test-bed."

By investigating the flight pattern and behaviour of the tsetse fly, scientists say they will then be able to place impregnated fly traps to the best effect.

First, however, the researchers will have to shrink the device by two- thirds so that it can be fitted to the tsetse.

Dr Riley explained how the technology works. "The harmonic generating tag reflects the radar signal at a different frequency which means it can be picked up in spite of the echoes from the ground. The insects are then tracked by a special radar scanner with two dishes - one to send the signal out and one to receive it ... It's rather like the security tags you find on clothes in shops."