The Ins and Outs of Butterfly Wings

October 8, 2013

Nature Notes by Bill Dunson

Butterfly watching has become a popular past time and the amount of variation within and between species provides a challenge in identification. Some species vary between the sexes, may have several color morphs, and may vary seasonally in color/pattern. One intriguing complexity is the variation in appearance between the inside and outside of the wings. Let’s consider some of the major pattern differences and what their purposes might be.

I have not found any overall summary of butterfly wing patterns but suspect that one of the most common is a relatively brighter color inside the wings and a more camouflaged coloration outside. The red admiral is a good illustration of this. Sexes are the same and the inside of the wings have several red/orange bands that make the butterfly very conspicuous when the wings are held open while sunning or foraging. In contrast when the wings are closed, it is difficult to distinguish the butterfly from a natural background. I have been unable to find a definitive function for the bright inner wing coloration, but it seems likely that species recognition may be involved. What is surprising is that such a brightly colored butterfly is apparently not advertising toxicity. The alternation between cryptic and bright colors as the wings are opened and closed might tend to confuse predators. This species migrates long distances and is found widely throughout the planet.

On the other hand the silver spotted skipper found throughout the eastern US has a very obvious white spot on the outside of the hindwing, whereas the inside of the wings are cryptically colored. This is a very common species and certainly the lack of camouflage does not seem to be a problem. It would be interesting to paint over the white spot and see what the effects would be on interactions with other members of the species and on predation. There is some debate about the occurrence of territoriality in butterflies which could be using species specific marking to advertise themselves and defend nectar sources.

Then there are some butterflies that are colored similarly both inside and outside of the wings. The meadow fritillary illustrates this situation. The wing coloration seems to be a type of disruptive pattern that allows the butterfly to blend in with variegated natural backgrounds.

You will observe these and many other colors and patterns among butterflies you observe in your garden and elsewhere. Clearly there is a fertile field for investigation of the purposes of the many and often quite spectacular color patterns of these “flying flowers.” So enjoy them for their beauty but also think about the reasons for these fascinating insects to have such remarkable colors.

Bill Dunson, Englewood, FL, and Galax, VA

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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