Magnificent Morpho Iridescence

This is my very first post, and I thank you for taking the time to have a look at The Insect Room. I hope this will be a place you can return to regularly to check out the marvels of the insect world.

Morpho is a genus of butterflies hailing from tropical Central and South America. The males of many species are noted for the brilliant, iridescent blue colouration of their wings. Flashes of light reflecting off the wings of a Morpho can reportedly seen up to 1km away. The sheer beauty of the Morpho was, ironically, cause for some of the Native peoples of the Americas to consider it an evil spirit. This reputation was fostered by legends of enchanted admirers following the butterfly into the the jungle, never to be seen again! Below are a couple of photos of the Peruvian jungle, home to several Morpho species...

Let's investigate exactly what it is about a Morpho's wings that lead to such brilliant colouration and iridescence.....

Morpho didius - one of the more common Morpho species, often used in artworks and in insect displays

Morpho rhetenor, along with Morpho cypris are considered the most brilliantly blue coloured of the Morpho species

Not all species of Morpho are blueThe species Morpho has a pearlescent appearance. 

Morpho hecuba (the Sunset Morpho) is the largest species of Morpho, with some specimens reaching  20cm in wingspan. 

What's in a wing?

To start, we need to have a closer look at the Morpho's wings. Magnification of around x reveals that the wings are actually composed of thousands of tiny little scales laid out in a way that they somewhat resemble roof tiles...

However, we must go even closer to gain further understanding. Zooming in a little further, we can see that the scales possess a streaked appearance...

Further magnification reveals that these streaks constitute parallel ridges and recesses; components of a complex micro structure within each scale...

Taking a cross section through this microstructure, it is revealed that each ridge has a number of shelf like branches of equal length....

The complex structure interacts with light in such a way that only blue light is reflected...

The change of an objects colour according to the angle of viewing is known as "iridescence" and is readily observed in such substances as soap bubbles and clam shells. In the Morpho butterfly, iridescence results from the fact that the microstructure of the scales reflects blue light better at certain angles than others. Thus depending on the position of the light source and the angle of viewing, the shade and intensity of colour can vary. At certain angles, areas of the wing can seem to have no blue colour, instead appearing browny grey. This reveals the "true" colour of the wings in that the structures contributing to iridescence in themselves contain no blue pigment (pigment being a chemical substance that generally reflects a certain colour, regardless of the angle of viewing). This underlying brownish grey of the Morpho is witnessed in areas of the butterfly that do not have scales of the above structure, such as the underside. 

This artwork composed of wings of Morpho aega shows 

clearly the effect the angle of light/viewing exerts on 

appearance. Some wings are a brilliant blue while others 

appear the "natural" underlying grey/brown colour

Sheer Beauty...

Anybody who has witnessed the shimmering iridescence of a Morpho butterfly with their own eyes can attest to the fact that it is one of nature's most beautiful sights. So much so that Japanese textile designers have used nanotechnology in attempt at recreating the microstructure of a Morpho's scales in fabric. The result is Morphotex. Nice, but nowhere near God's original design!

A Morphotex dress