Bee numbers have been falling dramatically and scientists are trying to understand why. In the past 25 years honey bee numbers in England have more than halved and they are still decreasing. It is a similar story elsewhere in the UK and in other countries.

Bees of all types - there are hundreds of them - play a huge role in the life of the countryside and a third of what we eat is reliant on bee pollination. Studying the behaviour of these complex insects is crucial to finding out what is happening but it is also a big challenge.

A honey bee can visit several thousand flowers in one day and navigate over several kilometres, so how do you track one?

Scientists are using harmonic radar technology. A radar transmitter emits a signal which is received by a tiny antenna glued on a honey bee's thorax (back). A small diode in the centre of the antenna converts it into a different wavelength that can be detected and followed.

The converted signal is unique. There is no other source in the environment, so scientists know it's the tagged honey bee. A portable radar tracking station is used to transmit the signal and gather the information sent back.

The answer
A tiny antenna is glued to the thorax of the insect
A radar transmitter emits a signal
A diode in the centre of the antenna converts it into a unique signal that researchers can track 

A honeybee with an antennae glued to it 
  • A single bee can visit

    1,000+

    flowers a day

  • A bee's wings beat

    200

    times a second

  • Every year, bees produce

    6,000

    tonnes of honey in the UK

Honey bees fly up to 4 miles (6.5km) to collect nectar and pollen and can cover 50,000 hectares.

bees

Each antenna is stuck to the honey bees by hand. Test bees are prepared by gluing a small plastic disc with an identification number on to the bee's thorax using strong double-sided adhesive. An antenna is later attached to the disc, again using adhesive.

The honey bee is caught by attaching a long plastic tube to the entrance of a hive. As the insects come and go two gates are dropped down, like portcullises, to trap one in-between. The antenna is removed the same way when the honey bee returns.

The signal sent from the tagged insect shows as a "blip" on a radar screen, scientists compare it to watching the moving dots on a ship's radar screen. It accurately shows how far away the honey bee is and in what direction it is flying. A computer programme is then used to reconstruct the honey bee's flight path from the "blips".

"This can be overlaid on maps of the area to accurately show where the insect has flown and the landscape features of that area," says Dr Jason Chapman, a radar entomologist at Rothamsted.

The technology was originally developed to study the tsetse fly in Africa, which spreads the potentially fatal sleeping sickness. The antenna was too big to tag the flies but works well with bees because they are larger.