The sweet smell of success
3 November 2008
New research shows that bumblebees rely on the floral scent carried by nest mates to point them towards the best flowers.
A bumblebee forages for nectar.
Dr Mathieu Molet, Professor Lars Chittka and Dr Nigel Raine at Queen Mary, University of London (QMUL) have shown that bumblebees learn from the floral scents carried into a hive by returning foragers.
And these scents affect their choice of flowers when they forage themselves.
Foraging for nectar is a long and dangerous business for bees. Even when they find flowers there is no guarantee they'll find much nectar.
Honeybees tell nest mates on which flower type they fed by passing scented nectar mouth-to-mouth. But bumblebees don't do this.
Bumblebees returning from a successful foraging trip release a foraging recruitment pheromone - chemicals produced by the bees to change the behaviour of their nest mates. The pheromone tells other worker bees to go out foraging, but cannot tell them where to look.
Instead they detect the scent of nectar-rich flowers from different sources in the nest. According to the paper, published in the journal Naturwissenschaften, the bees change their behaviour most dramatically if they pick up the scent from other bees.
By favouring flowers visited by nest mates, bumblebees reduce the amount of time spent looking for nectar, making foraging trips more efficient.
The research team allowed bees to forage amongst ten artificial flowers. Five of the flowers were scented with anise and five with peppermint.
The bees initially preferred the peppermint scent but their preference changed when researchers introduced the anise scent into the nest; either in the air, in a honeypot or on another bee.
Radio-tagged bumblebees in an artificial nest
The effects of the anise scent were dramatic. The anise scent in the air of the nest caused the bees to visit anise-scented flowers more frequently.
'Scent in the air was sufficient for learning" says lead author, Molet, a post-doctoral researcher at QMUL. When bees in the nest smelled the anise scent on another bee, however, they visited anise-scented flowers first almost every time.
The researchers point out that rats respond in a similar way to food scents. Some rats learn what is worth eating by smelling food odours on the breath of other rats. 'If another individual does something rewarding, it is worth doing the same thing.' said Molet.
The bumblebee work is part of an on-going series of studies to investigate the use of artificial foraging recruitment pheromone on bumblebee nests.
'The ultimate outcome is to improve crop pollination in greenhouses.' adds Molet.
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