Bees pollinate about one-third of what we eat so it is important that we know as much about them as possible.
In a study published today in Current Biology, researchers provide new information about the vision of bumblebees, adding to our knowledge of how they detect and identify flowers.
Professor Julian Partridge of The University of Western Australia's School of Animal Biology is senior author of the paper, which describes experiments undertaken at the University of Bristol in the United Kingdom.
The team found for the first time that bumblebees could learn to make use of polarisation patterns on artificial flowers - but only from flowers that are downward facing, or pendant. Pendant flowers represent a high proportion of angiosperm species, which are the most economically important plants and include most agricultural crops, garden flowers and many common shrubs and trees. The work also showed that real flowers have polarisation patterns.
It was known that bees - and some other animals - are sensitive to polarised light and that bees make use of it for sun-compass navigation. Humans cannot see the polarisation of light - although we do wear PolaroidTM sunglasses to shield our eyes from polarised glare, such as that reflected from water surfaces.
However, to a foraging bee, polarisation signals on flowers join the array of floral signals such as colour, patterns, shape, texture, temperature, humidity and electric fields that act together to make bees recognise flower species and enhance their foraging efficiency.
To find out if bumblebees could learn polarisation patterns on flowers, the researchers created artificial ‘flowers' and a flying arena. Bees flew into the arena, visited the ‘flowers' and learnt to differentiate between rewarding, or sucrose-providing ‘flowers' with one pattern of polarisation and aversive, or quinine-providing flowers which had a different pattern of polarisation.
The authors said that because bees could only learn polarisation cues from pendant ‘flowers', it was possible they used the same polarisation-sensitive upper part of their eye that they used for navigation.
"Bumblebees are known to take flower orientation into account when foraging as this saves them handling time," the authors wrote.
They said polarisation patterns on real flowers, that were invisible to humans, may provide cues to make foraging easier for bees.