Database shows how bees see world in UV

Researchers are being offered a glimpse of how bees may see flowers in all their ultra-violet (UV) glory.

The Floral Reflectance Database (FReD) was created by researchers at Imperial College London and Queen Mary, University of London.

It enables researchers to "see" plant colours through the eyes of bees and other pollinating insects.

Bees have different colour detection systems from humans, and can see in the UV spectrum.

Details of the free database are published in the open-access journal PLoS ONE.

"This research highlights that the world we see is not the physical or the 'real' world - different animals have very different senses, depending on the environment the animals operate in," said Professor Lars Chittka from Queen Mary's School of Biological and Chemical Sciences.

"Much of the coloured world that's accessible to bees and other animals with UV receptors is entirely invisible for us. In order to see that invisible part of the world, we need this special machinery."

The researchers collected what's called "spectroreflective" measurements of the petals and leaves of a large number of different plants. These measurements show the colour of plants across both the visible and invisible spectrum.

Users of the database can then calculate how these plants appear to different pollinating insects, based on studies of what different parts of the spectrum different species see.

Scientists have inferred what colours insects see by inserting microelectrodes into their photoreceptors, and by using less invasive behavioural studies.

Seeing the world as insects may see it can reveal "landing strips" which are invisible to the human eye. These act to guide insects to the nectar they feed on.

These landing strips might take the form of concentric circles of colour or dots.

"Quite often, you will find in radial symmetrical patterns that there is a central area which is differently coloured. In other flowers there are also dots in the centre which indicate where there is basically an orifice for the bee to put in its tongue to extract the goods."

Greenhouse use

Creeping Zinnia as we see it (left) and with UV shades made visible (right)

But what is the point of such a tool beyond giving researchers an insect's view?

Professor Chittka says seeing these invisible colours may have commercial applications in the greenhouse and beyond.

"Every third bite that you consume at the dinner table is the result of insect pollinators' work. In order to utilise insects for commercial pollination purposes, we need to understand how insects see flowers.

"We need to understand what kind of a light climate we need to generate in commercial glass houses to facilitate detection of flowers by bees."

Co-author Professor Vincent Savolainen, from Imperial College London, says the database also offers us new perspectives on how plant colour evolved.

"We hope this work can help biologists understand how plants have evolved in different habitats, from biodiversity hotspots in South Africa to the cold habitats of northern Europe," he says.

"FReD's global records may show how flower colour could have changed over time, and how this relates to the different insects that pollinate them, and other factors in their local environment."