WEBVTT - How Do Butterflies Get Their Brilliant Colors?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff

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<v Speaker 1>Lauren vogelbaumb here. Butterflies possess some of the most striking

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<v Speaker 1>color displays found in nature, especially considering their small size.

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<v Speaker 1>As they fly from flower to flower gathering nectar, their

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<v Speaker 1>brightly colored wings shimmer and shift before your eyes. Pilots

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<v Speaker 1>flying above the rainforests of South America can see the

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<v Speaker 1>bright blues of the morpho butterfly up to half a

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<v Speaker 1>mile away. A butterflies patterns and colors can act as camouflage,

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<v Speaker 1>help identify or attract mates, or confuse or worn off predators.

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<v Speaker 1>Part of what makes butterflies colors so intense is that

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<v Speaker 1>you're not just looking at ordinary pigmented color. They also

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<v Speaker 1>have what's called structural color, which appears when the physical

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<v Speaker 1>structure of a surface has tiny layers and shapes that

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<v Speaker 1>reflect light to your eyes in specific ways. Okay, many

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<v Speaker 1>things in nature get their color from chemical pigments that

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<v Speaker 1>absorb certain wavelengths of light and reflect others. For example,

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<v Speaker 1>the pigment chlorophyll gives many plants their green color. The

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<v Speaker 1>chlorophyll soaks up the blue and red wavelengths of the

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<v Speaker 1>spectrum but not the green, so that's what you see

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<v Speaker 1>when it bounces off a plant to your eye. Most

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<v Speaker 1>butterflies get their different shades of brown, gray, and black

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<v Speaker 1>from melanin, which is the same pigment that might make

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<v Speaker 1>your skin deepen or tan or freckle in the summer

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<v Speaker 1>and can help give humanize their color. Some butterflies with reds, oranges, yellows, creams,

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<v Speaker 1>and even blues and blue greens get that color from

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<v Speaker 1>various pigments, but structural color doesn't come from pigments. We

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<v Speaker 1>talked about this a bit in our episode about human

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<v Speaker 1>eye colors. Human eyes never contain any blue pigment. Rather,

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<v Speaker 1>eyes that are pure blue have very low concentrations of

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<v Speaker 1>melanin in the iris, so when light hits that pale

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<v Speaker 1>but still textured and fibrous iris, the light scatters, and

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<v Speaker 1>blue light happens to scatter really well, so that's what

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<v Speaker 1>we perceive. Butterfly wings are made up of wafers of kitan,

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<v Speaker 1>given support and shape by a structure of veins. Kitan

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<v Speaker 1>is the same strong stuff that our hair and nails

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<v Speaker 1>are made of, and makes up butterflies and other insects

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<v Speaker 1>exoskeletons too. It's transparent by itself, but can carry pigments

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<v Speaker 1>and or structural color. If you look closely at a

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<v Speaker 1>butterfly's wings with your naked eye, you might notice it

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<v Speaker 1>looks a little soft or fuzzy, feathery, or sort of satiny.

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<v Speaker 1>That's because their wings are covered in thousands or millions

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<v Speaker 1>of tiny scales, overlapping like tiles on a roof. The

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<v Speaker 1>name of their taxonomical order means scaled wings. These scales

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<v Speaker 1>are each less than one hundred micrometers in size, smaller

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<v Speaker 1>than the width of a human hair or a droplet

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<v Speaker 1>of mist on a foggy morning, and these scales often

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<v Speaker 1>do contain pigment like melanin, but it's sometimes the microscopic

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<v Speaker 1>shape of the surface of the scales that gives a

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<v Speaker 1>wing its color, just like with human eyes. The most

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<v Speaker 1>vibrantly blue butterflies contain no blue pigments. The microstructure of

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<v Speaker 1>butterfly scales can come in different shapes that produce different

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<v Speaker 1>colors and effects on different species. So let's take the

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<v Speaker 1>blue morpho butterfly for example. Its wings are a shimmering

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<v Speaker 1>blue that can look almost aqua to near indigo, depending

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<v Speaker 1>on how the light hits them and the angle that

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<v Speaker 1>you're observing them from. A couple of things are happening here.

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<v Speaker 1>The overall blue color comes from the structure of the

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<v Speaker 1>blue morphose scales. Each blue scale has a surface covered

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<v Speaker 1>in many rows of tiny tree shapes. If you look

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<v Speaker 1>at it under a scanning electron microscope like you do,

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<v Speaker 1>each row looks sort of like the cross section of

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<v Speaker 1>a lego pine tree, like if you took a little

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<v Speaker 1>cookie cutter in the shape of a spindly Christmas tree

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<v Speaker 1>and pushed plato through it to create a long rope

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<v Speaker 1>in a tree shape. And each scale has an orderly

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<v Speaker 1>orchard of these tree shaped rows on it. These shapes

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<v Speaker 1>are transparent, but when normal full spectrum light shines onto

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<v Speaker 1>the scale, it hits the top of these tree rows

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<v Speaker 1>and bounces off of each branch on the tree. And

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<v Speaker 1>there's about six to ten branches, and these microstructures are

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<v Speaker 1>just the right shape and size to reflect blue and

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<v Speaker 1>only blue light. The rest gets scattered or absorbed by

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<v Speaker 1>the brown melanin on the undercoating of the scales. Notably,

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<v Speaker 1>this only word an open air. If you get the

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<v Speaker 1>scales wet, that changes how light reflects off of them,

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<v Speaker 1>and they'll appear clear with the brownish undercoating. But okay,

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<v Speaker 1>what about the iridescence of the butterfly's wing. Iridescence is

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<v Speaker 1>the quality of colors shifting as your point of view changes.

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<v Speaker 1>You can see it in mother of pearl, on fish scales,

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<v Speaker 1>and on peacock feathers. It happens when light passes through

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<v Speaker 1>a transparent, multi layered surface and is reflected towards your

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<v Speaker 1>eye more than once. The multiple reflections can compound one

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<v Speaker 1>another to intensify colors, or can disrupt one another to

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<v Speaker 1>dim or cancel out colors as the light travels to

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<v Speaker 1>your eye. It's helpful here to remember that light is

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<v Speaker 1>a wave and can be described as a wave length,

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<v Speaker 1>a wavelength being the distance between identical points on a wave.

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<v Speaker 1>A waves can also be described by their phase, the

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<v Speaker 1>position of their crests or high points, and trough or

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<v Speaker 1>low points. When two waves have the same phase, their

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<v Speaker 1>crests and troughs would align if you stack them on

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<v Speaker 1>top of one another. A simple example of iridescence is

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<v Speaker 1>the colors that appear on soap bubbles. The soap self

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<v Speaker 1>is transparent and the bubble's surfaces are reflective, so a

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<v Speaker 1>light first passes through the bit of the bubble that's

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<v Speaker 1>closest to you, which reflects some of that light to

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<v Speaker 1>your eye. But light also passes through to the far

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<v Speaker 1>bit of the bubble, which also reflects some light back

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<v Speaker 1>to you. Depending on the time it takes the second

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<v Speaker 1>reflection to join the first, plus a few other factors,

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<v Speaker 1>the two waves may or may not line up or

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<v Speaker 1>have the same phase. If the phase of the two

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<v Speaker 1>waves is different by some multiple of one full wavelength,

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<v Speaker 1>the waves are said to have constructive interference. If the

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<v Speaker 1>two waves differ by half a wave length or an

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<v Speaker 1>odd multiple of debt, they have destructive interference. The math

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<v Speaker 1>there is a little beyond our scope today, but basically,

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<v Speaker 1>the degrees of constructive and destructive interference change as your

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<v Speaker 1>point of view changes, thus bringing different colors to your eye.

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<v Speaker 1>Here's how it works. Constructive interference causes two waves to

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<v Speaker 1>complement each other and thus amplify a given color. That's

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<v Speaker 1>why eardescence can create such intense, almost glowing colors. Destructive

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<v Speaker 1>interference causes the two waves to cancel each other out,

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<v Speaker 1>dimming a given color. So bouncing off of a single

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<v Speaker 1>and technically transparent surface you'll see different colors or shades

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<v Speaker 1>as those factors of distance and interference change. The same

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<v Speaker 1>principle of eardescence behind soap bubbles applies to a blue

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<v Speaker 1>morpho butterfly's wings. Because of the structure of the aforementioned scales,

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<v Speaker 1>the branches on the turn and the heights of the

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<v Speaker 1>different rows create multiple reflections that can constructively or destructively

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<v Speaker 1>interfere with each other. This changes the exact intensities and

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<v Speaker 1>shades of blue that hit your eye from different portions

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<v Speaker 1>of the wing, or as the butterfly moves, or as

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<v Speaker 1>you move around it, and again. The blue morpho is

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<v Speaker 1>just one species of butterfly. Other species in the genus

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<v Speaker 1>and other genera of butterflies have microstructures on their wing

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<v Speaker 1>scales that produce entirely different colors and effects. For example,

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<v Speaker 1>the peacock's swallowtail has tiny cups on its scales that

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<v Speaker 1>reflect yellow from the bottom but blue from the sides.

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<v Speaker 1>The two colors combine to appear green when you look

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<v Speaker 1>at the wing head on, but if you look at

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<v Speaker 1>it from the flat edge, you can only see the blue.

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<v Speaker 1>Some structural color displays on butterflies even extend into the

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<v Speaker 1>ultraviolet part of the spectrum, which is visible to those

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<v Speaker 1>butterflies but not to humans and not even to all

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<v Speaker 1>other butterflies, thus helping them identify potential mates and beyond displays,

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<v Speaker 1>the structure of the scales can help butterflies manage things

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<v Speaker 1>like water runoff and body temperature. These microstructures are so

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<v Speaker 1>intricate that we don't know how to replicate them yet,

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<v Speaker 1>but researchers hope that studying how butterflies build their wing

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<v Speaker 1>scales will help us figure out how to build better

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<v Speaker 1>and more beautiful materials in the future. Today's episode is

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<v Speaker 1>based on the article where do Butterflies get their striking colors?

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<v Speaker 1>On how stuffworks dot Com written by Jennifer Horton. Brainstuff

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<v Speaker 1>is production of iHeartRadio in partnership with how stuffworks dot

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<v Speaker 1>Com and is produced by Tyler Klang. Four more podcasts

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