FoundationalConceptsNeuroscience

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Visible Light

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Figure 11.4. Electromagnetic spectrum.

Some 60 years ago, many biologists thought that bees and other insects

were totally color-blind animals. I was unable to believe it. For the bright

colors of flowers can be understood only as an adaptation to color-sen-

sitive visitors. This was the beginning of experiments on the color sense

of the bee. On a table outdoors I placed a colored paper between papers

of different shades of gray and on it I laid a small glass dish filled with

sugar syrup. Bees from a nearby hive could be trained to recognize this

color and demonstrated their ability to distinguish it from shades of

gray.

Honeybees also have visual capacities that are unusual from a
human perspective. Figure 11.5 shows an African daisy (Dimor-
photheca aurantiaca) illuminated by sunlight and photographed with
alens that captures only visible light (left) and one that also captures
ultraviolet light (right). Honeybee visual sensitivity extends into
the ultraviolet region of the electromagnetic spectrum, a range of
energies to which we humans are blind. There is abundant ultraviolet
radiation in sunlight, and many flowers have patterns that are visible