HOW DO BEES SEE?   by Wayne Handlos


Human view of a flower (left) and a bee’s view  (right)           



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 Any observation of the geraniums/pelargoniums in your garden will probably impress you with the number of bees visiting

the flowers. Especially in areas with a Mediterranean climate, where plants like lavenders and rosemary are commonly grown,

honey bees can be found in abundance. The small lavender flowers seem to be particularly attractive to these bees. At some

times the plants are positively abuzz with numerous bees. But have you stopped to think what these insects are doing on the

flowers? And, how do bees find these flowers? What benefits, if any, do the plants derive from the bees’ visits?

We generally give the answer that bees come to flowers to collect nectar to make honey; and, in return the flowers get pollinated

and produce seeds from which new plants can grow. These simple answers are only the tip of the iceberg of the relationship

between plants and insects. Whole books have been written especially about bees amongst the insects associated with plants.

 Their colonial life style has attracted much attention. The cooperative functions carried out by these creatures have intrigued and

attracted many scientists, as well as many amateurs. The relationships between plants and animals has also attracted many people

over the decades and books have also been written about the pollination/food relationships between plants and animals. These

"pollination syndromes" have been described in detail and even carry their own vocabulary; melittophily (bee pollination); chiropterophily

 (bat pollination); phalaenophily (moth pollination).

In a subsequent article I will describe the complexities of pollination and pollinators amongst the various species of Pelargonium.

But for now I will look at bees (especially honey bees which have been the most intensively studied insect) and their vision.

Since flowers provide most of the food for bees, it is obvious that finding flowers is of prime importance in the life of a bee. Because

bees are active during the day, it is obvious that vision is probably the primary ability that bees use for locating food sources. A close

ook at a bee’s head reveals large, compound eyes. What can these eyes detect? The compound eye is composed of many individual

lenses. Each of these connects to the bee’s brain. Each of these lenses is basically a small version of our own eye. In terms of vision

the bee’s eye contains receptors, like our own eyes. Extensive studies show that both humans and bees have three different types of

cones in their eyes. We might assume then that we see what bees see, but this assumption has been shown to be incorrect. Each type

of receptor responds to different wavelengths of light. In humans, our cone cells respond to red, green and blue wavelengths of light.

 In honey bees their three types of receptors respond to green, blue and ultraviolet wavelengths of light. We cannot see ultraviolet wave-

lengths of light while bees do not detect red wavelengths of light. Various studies of the bees’ eyes and their photoreceptors have

demonstrated the validity of the above statements. So, in order to see what a bee sees we have to see what wavelengths of light are

being reflected by flowers. Various studies have been done with special cameras to visualize how a flower will appear to a bee. These

 investigations reveal another whole world of flowers that is different from what we see. We’ll investigate this topic in more detail in next

month’s newsletter.