Smells can be very powerful triggers of memories in humans, but what about in other animals? Judith Reinhard and colleagues at The Australian National University wondered whether scents could trigger navigational memories in honeybees. They designed a set of compelling behavioural experiments to see if honeybees could use scents to help them make their way back to a known food source (p. 4373).

Reinhard knew that honeybees have a keen sense of smell and are notoriously good at navigating to sweet-smelling flowers. But could these animals associate an attractive scent with a visual memory of the route to a specific location? The team needed to show that sniffing a particular smell only triggered a navigational memory in specific bees: those that linked the odour to a memory of the location of a tasty food reward.

Rigging up an artificial feeder, the team first tempted a group of honeybees to home in on an attractive rose scent, luring them with a tasty sugar snack. The insects quickly learned to navigate their way towards the location of the rose-scented feeder. The team expected that rose scent released in the beehive would trigger the bees' memory of the location of the rose feeder and send them off in the right direction. But would the smell trigger a foraging frenzy in all the other bees in the hive too? The team decided to train a second set of bees in the hive to forage at a second feeder, this time lured by a tangy lemon smell. They hoped that when bees in the hive caught a whiff of rose, lemon-trained bees would stay put while the rose-trained bees would set off in a hurry, using the navigational memory triggered by the scent.

Sure enough, when the team fanned rose aroma through the trained bees'hive, nearly all the rose-trained bees went flocking to the site of the feeder despite the fact that it no longer smelled of rose, while the lemon-trained bees stayed safely tucked up at home. The rose scent had triggered a navigational memory in the rose-trained bees only. Reinhard was pleased with this clear evidence that a scent triggers a very specific navigational memory in honeybees.

The next step was to see how many scents the brainy bees could remember. The team found that a single bee could associate two different scents with two different locations. They were even more impressed to find that bees could learn to associate two different scents with two different colours, even when the coloured feeders were moved around to different locations. The bees were doing so well that Reinhard was confident that they would be able to remember three different locations associated with three different scents. She was astonished when she discovered that this was a step too far. Intrigued by the limits to the insects' amazing memory, Reinhard is now setting out to investigate how complicated things can get before the bee's brain is baffled.

Reinhard, J., Srinivasan, M. V., Guez, D. and Zhang, S.(
). Floral scents induce recall of navigational and visual memories in honeybees.
J. Exp. Biol.