Friday, 10 August 2012

A bees eye view of flowers

Posted by Sue Southway, Plantlife's Wildflowers Count Survey Officer

We are at a time of year when wild flowers brighten up our countryside. Predominant colours are white, yellow, shades of pink, blues purples, and all of them are trying to attract insects to pollinate them. However the colours that we see do not look the same to the bees.

Common silverweed as we see it (top) and
under UV light (below).  © Bjørn Rørslett/NN 
Bees and other insects see in the ultraviolet spectrum of light, and this means blues, greens and violet shades, and they cannot see red at all, to them it appears black. A look at a guide to British wildflowers shows that there are very few native red flowers with the poppies being the truest red. In tropical areas many flowers that are red will be pollinated by mammals such as bats that are attracted to the bright colour.

So how do plants attract the bees? The answer is that they produce designs that we cannot see unless we use UV light, and they light up the pollen producing area luring the bees in.

The photo above-right (courtesy of www.naturfotograf.com) shows two images of Common Silverweed, Potentilla anserina. The first, the one on top, is how we see it - entirely yellow. Under ultraviolet light, however, a dramatic change occurs. A clear target has been provided for the bees to aim at.

Meadow cranesbill as we see it (top) and
under UV light (below).  © Bjørn Rørslett/NN 
The pattern has been highlighted in red in the second image (the bees, of course, will not see it as red, this is only so we can see it ourselves. How exactly they perceive the pattern no-one is entirely sure).

The photo of Meadow Cranesbill, Geranium pratense on the left, shows a similar effect: a pattern is created in the UV spectrum that acts to attract the bees to the pollen at the heart of the flower. There is evidence to show that the chemical compounds producing these patterns can also deter herbivorous insects, in particular caterpillars, protecting the plant’s reproductive capability.


If you would like to help us keep track of some our most common wildflowers, why not sign up for Wildflowers Count - the UK’s only annual national wild plant survey? 2012's survey is still active until the end of August. Find out more at www.plantlife.org.uk/wildflowerscount

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