The human eye is a thing of mesmeric beauty and fascination. Indeed, its form and function are so perfect that it has been proposed as proof of divine creation. It even caused Charles Darwin to cast doubt on his own evolutionary theory – in the “Origin of Species” he voiced his disquiet at the notion that something as flawless as a human eye “could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.” The human eye is a sublime piece of apparatus.
A close-up of a bee’s eyes, on the other hand, is strikingly alien. Is it that we simply do not consider insects to have “faces”, or is the miniature scale of an insect’s physiognomy just too small for us to register ? Then again, perhaps it is because bees don’t have two eyes. They have hundreds of them.
In common with most insects, the honey bee has compound eyes. These are large, dark ovals in which hundreds of single eyes (called ommatidia) are arrayed next to each other, each with its own lens and each looking in a different direction. This does not mean that the bee sees lots of little pictures, as each ommatidium contributes a pixel to the overall image perceived by the compound eye and organised in the bee-brain.
There are other important differences between the bees’ view of the world and ours: the bees see colours differently. We base our colour perceptions on red, blue, and green parts of the spectrum, yet bees use a palette of ultraviolet, blue and green and are “colour blind” to red (although they can see red-tinged wavelengths such as orange and yellow). Research suggests that bees’ favourite colours are purple, violet and blue (which is just as well, since my basic planting advice for absolute novices is that they can’t go too far wrong using these colours for bee-forage!)
And then there are the bees’ ocelli (“little eyes” in Latin). These are a triangular grouping of 3 simple eyes on the top of the bees’ heads, each of which focuses light through a single lens and helps the bees fix on the sun’s orientation so they can navigate precisely to and from the hive during daylight.
But a fascinating recent discovery, discussed in Juergen Tautz’s “The Buzz About Bees” (pg 80) has been that, while bees use their full visual capacity in outbound foraging journeys and in collection, they switch to a basic black and white vision on their high-speed return journey to the hive. Once the foraging job is done, the colour sensitivity of the bees’ eyes becomes superfluous and they become fast-forward homing devices.
If you’re reading this on your commute home from work, you’ll know exactly how that feels !