Butterfly adaptations to blend in, show off and shimmer
The phenomenal variety of colors on butterfly wings are sorted into patterns that repeat from right to left wing, but vary from the top sides of wings to the bottom sides. To our eyes, a single butterfly may boast practically the entire color spectrum, from red to violet, in patterns of circles, dashes, and splashes. It is challenging to figure out how natural selection has shaped this wild riot of colors.
If you look across butterfly species, though, you can see trends. Many butterflies have bright colors on top, and duller colors on the bottom. Lots of butterflies have repeating large, round spots along the edges of their wings that look like eyes painted on. The surfaces of butterfly wings are shimmery, their colors shifting when viewed from different angles.
To explain body patterns, scientists observe how animals behave in relation to their habitats. A fluttering butterfly is easy to see but hard to catch. In flight, bright butterfly wings create a flashing effect that may alarm predators, or make zeroing in on a butterfly harder. A perched butterfly often shows the duller side of its wings, perhaps concealing it from hungry birds or snakes.
Butterfly colors may also play a role in mate attraction. Every butterfly species has a unique set of color patterns. Some female butterflies vibrate their wings in a way that displays patterns that may announce their species to males. For colors to work in courtship, they must be visible to the eyes of the viewer. It turns out that butterfly eyes have large visual fields and extra color photoreceptors, supporting a rich, panoramic color vision.
Pigments, i.e. compounds that absorb certain light wavelengths and reflect others, are responsible for most of the colors humans and other animals see. But, blues in nature do not often come from pigments. Animals that look blue - Blue Jays or Peacocks or Blue Morpho Butterflies - are reflecting blue light in other, unique ways that have to do less with chemistry and more with structure.
Learn more about structural butterfly colors and how they relate to butterfly adaptations in a "Smithsonian Science How" webcast on Thursday, May 24, 2018. During Butterfly Adaptations – How They Come By Their Colors (airs at 11 a.m. and 2 p.m. EDT on the Q?rius website), Butterfly Pavilion Manager Eric Wenzel and Microscopy Educator Juan Pablo Hurtado Padilla will take you behind the scenes with butterflies while answering your questions live. You can also get teaching resources to use with the webcast.