Recently, enjoying a leisurely gin and tonic as the evening sunshine bathed my garden.
I wondered why the bees which were busy working a back shift were visiting some flower but ignoring others. So, when the evening began to cool down noticeably, I had recourse to the internet to satisfy my curiosity. And this is what I found.
Bees cannot see the colour red. While those of us who enjoy normal colour vision can differentiate between red, blue and green, bees share our appreciation of blue and green but make up for their red colour blindness by adding the facility to see ultra-violet light to their visual acuity. This means that bees see colours very differently to how they appear to us; and it also means that they can see colours which we cannot. And there is another very significant difference between the world we see and the world they see; bees, I learn, are … in human terms … very short-sighted. They have to get very close to any object to make out the details which enable them to understand what the object is. If, gentle reader, you have ever had an eye test, think of the test card the optometrist invited you to read, with letters in large, bold print at the top becoming progressively smaller and less bold as you progress down the card until you reach the point where you confess that you cannot tell which letters they are. Well, a bee with normal vision wouldn’t get far below the top line at the optometrist’s range.
The reason for this is that, while we enjoy the benefits of having large lenses in our eyes … so-called ‘simple’ eyes … bees have to make do with small, multi-faceted lenses which are great when you want to see the finest details up close … as with a magnifying glass … but rubbish if you are trying to see things clearly any more than a matter of maybe less than three feet away … again, think of trying to make sense of the view through a window seen through a powerful magnifying glass. The eyes of bees … and of a great many other insects … are ‘compound’ eyes; they are made up of many thousands of parts called ommatidia, each ommatidium being a tiny light-sensitive part of a compound eye, every one of them acting like an individual simple eye. Since every individual ommatidium points in a slightly different direction, bees and other insects enjoy a very wide angle of sight, which is why it is so difficult to kill that fly which always seems to see the would-be killer blow coming. These compound eyes are also excellent at discerning very rapid movement (think about the fly’s evasive talent); and a honey bee can see up to 300 pictures per second, while the human eye does well to achieve a rate of 65 images per second.
So the bees’ eyes generate pictures like a good camera set at 1/300th of a second; they have a very wide angle of vision; and they don’t see red. But that still doesn’t explain why they prefer some flowers over others. And this is where the bees’ ability to see ultraviolet light comes in; the bees not only see our garden flowers in different colours to the colours we see; they see ultraviolet light patterns and shapes on the flowers, patterns and shapes which are wholly invisible to us. So, having been attracted to my garden by the scents given off by many of my flowers and having found the flowers by detecting blurred blobs of colours which are not the same colours which I see, they home in on their nectar targets guided by their ability to see what we might call ‘ultraviolet nectar guides’ aided by their excellent close vision. Now I understand something about why the bees seem a bit confused as they approach flowers but are then very precise in their investigation of the individual blooms … both large and small … once they have begun their visit to the plant. And the next question is: how on earth do these bumbling bees they find their way back to the hive?