In many bee-pollinated flowers, there is a region of low ultraviolet reflectance near the center of each petal. This pattern is invisble to humans because our visual spectrum does not extend into the ultraviolet. Bees, however, can detect ultraviolet light. The contrasting ultraviolet pattern (called a nectar guide) helps a bee quickly locate the flower's center. This adaptation benefits both the flower (more efficient pollination) and the bee (rapid collection of nectar).
Click on the button below the picture to alternate between images of the flower recorded on "normal" film and on ultraviolet-sensitive film.