Combined Ultraviolet and visible light photo of Marsh Marigold flowers in Spring. The flowers appear plain yellow to the human eye, which cannot see ultraviolet light. Under ultraviolet light a clear 'hidden' pattern can be seen, with the centre of the flower being dark while the edges of the petals are bright.
Many insects can see in ultraviolet light, it is believed that the ultraviolet markings on some flowers, such as the Marsh Marigold, help guide insects to the centre of the flower where the pollen and nectar reside.
Caltha palustris (kingcup, marsh marigold) is a perennial herbaceous plant of the family Ranunculaceae, native to marshes, fens, ditches and wet woodland in temperate regions of the Northern Hemisphere.
It becomes most luxuriant in partial shade, but is rare on peat. In the United Kingdom, it is probably one of the most ancient native plants, surviving the glaciations and flourishing after the last retreat of the ice, in a landscape inundated with glacial meltwaters.
Description adapted from Wikipedia: http://en.wikipedia.org/wiki/Caltha_palustris
Visible light image in multiply blend mode over UV image. Curves adjusted.