But excellent vision at speed isn’t enough, as bees only have tiny brains and the process of just staying in the air and not flying into walls is pretty complex. So in order to simplify things, bees switch off colour vision at speed and fly in black and white. They only revert to colour when they slow down closer to flowers.
As the bee approaches the flower, it is guided by smell but also by ultra-violet patterns on the petals. Ultraviolet is invisible to humans, but the visual spectrum of bees has evolved so that instead of seeing a red-to-violet spectrum like humans, the bee vision spectrum is slightly shifted, and they see orange-to-ultraviolet. So bees can see UV at one end of the spectrum, enabling them to see the UV patterns on flowers, but they can’t see the colour red at the other end. They can still see red flowers like poppies, but they appear black to a bee.
When the bee lands, it searches for nectar, and the flower needs to calculate precisely how much nectar to provide. It needs to provide enough to attract a bee, but not so much that it can fill up in a single visit, as pollination will only occur if the bee visits several flowers.
So each flower produces a small amount of nectar, and when there is none left, the bee leaves a scent on the flower to say ‘empty’. The scent wears off when the flower has created more nectar.
