MR Charles Green (Your Letters, May 27) was kind enough to comment enthusiastically on the miniature radar transponders we used to keep track of honeybees in flight.

He asks, as a beekeeper of many years' experience, whether the bees were not alienated from their sisters by this equipment and how they were able to manoeuvre within the height constraints of the hive.

The antenna of the transponder was indeed too long to allow bee recruits to move about in the hive, so each device had to attached (by a deft bee handler!) when a bee left the hive, and removed when it returned home.

This rather intricate process of rapid attachment and removal was made possible by the use of tiny discs of very thin, double-sided sticky tape, and a specially extended, transparent entrance to the hive.

Mr Green also asked about the weight of our transponders. These weigh between 3 and 12 milligrams, depending on the degree of mechanical robustness required; the ones used in the bee studies were the 12mg 'ruggedised' versions, and were thus about 10 per cent of the bees' weight. Foraging honeybees can carry up to 100 per cent of their bodyweight in nectar or pollen, so the 10 per cent transponder load was easily managed by our recruits.

It's perhaps worth mentioning that we achieved an unusual degree of miniaturisation with the transponders because they were designed to work without a battery - the energy to operate them was transmitted directly from the radar itself and this process worked up to a range of about 1 kilometre.

JOE RILEY, Peachfield Road, Malvern.