Asked by: Lyndon Roy, WimbledonWhen honey bees become alarmed (usually in response to a perceived threat to the hive) they emit the strong-smelling pheromones isopentyl acetate and 2-heptanone. These compounds stimulate an alarm response in other bees, which in turn produce similar pheromones, so that soon all the bees are in a state of alarm, and ready to attack anything that appears to be an intruder. Smoke acts by interfering with the bees' sense of smell, so that they can no longer detect low concentrations of the pheromones. In technical terms, the smoke reduces the electroantennograph response of the antennae. Strong floral odours can have a similar effect, but professional bee keepers have generally stayed with smoke, perhaps because they have more experience with it, and possibly also because it's cheaper. Either way, the effect is reversible, and the responsiveness of bees' antennae gradually returns within 10-20 minutes.