Ultraviolet Flowers, Infrared Trees
As humans, we have a very reduced visual spectrum. We can only catch light within certain frequencies, as Newton demonstrated this by dividing light using a prism (a beam of light contains the colors of the rainbow, because colours are wavelengths – the longer wave we can see is red, followed by orange, yellow, green, cyan, blue, and violet, the shortest wave. Whatever falls outside those frequencies – infra-red and ultra-violet – escapes our eye). But this is not the case for other animals.
Bees, for example, can detect ultraviolet light. If a plan depends on insect pollination, it is definitely advantageous for it to also have ultraviolet “colors” and patterns that can help bees and other nectar searching insects identify them. Birds can also see ultra-violet, and some feathers have markings we cannot se. There is, however, a downside to being sensitive to ultraviolet: sensibility to red decreases too (red is on the other end of the spectrum and all animals have a limited range – regardless of whether it matches ours or is displaced compared to it).
Mammals are not that lucky in regards to spectrum, because with the exception of some primates, they only have two cones (and red-green colorblindness). Birds, fish, reptiles, amphibians and some invertebrates, however, have three or more cones, and they can probably see better than we do.
Honeybees and bumblebees have trichromatic colour vision too, and are sensitive to ultraviolet (and consequently insensitive to red). If you think that’s impressive, wait until you hear about the Papilio butterfly, which has six types of photoreceptors making it only of the few lucky animals with pentachromatic vision. Still not wowed? The mantis shrimp has up to twelve spectral receptor types, which are thought to work as multiple dichromatic units. Bottomline: What we see is just a small portion of what is there. Luckily for us, we have devices to capture UV and UR light. Here are some incredible examples!
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