Introduction

The blue color on a Blue Morpho butterfly wing is not due to a pigment, it is due to microscopic structures on the butterfly wing.

Notice the blue color of the wings of a blue morpho butterfly. Blue Morpho Butterfly

A Blue Morpho Butterfly, Costa Rica

Looking through an optical microscope shows the blue scales on the wing of the butterfly.

Optical microscope view of Blue Morpho Scales. Click image to enlarge.

The scales are as wide as a human hair, about 0.1 mm.

The following images are Copyright 1995 by Bill May, used by permission.

The scales viewed through a scanning electron microscope, SEM.

In the SEM image the white bars are 100 micrometers long.

So, the scales are as wide as a human hair.

Increasing the magnification by an order of magnitude shows ridges on the scales.

Increasing the magnification by another order of magnitude shows details on the ridges.
In this image the white bars are 1 micrometer long.

The scales in the highest magnification images have ridges over a micrometer apart.

The ridges are made of more closely spaced rods, and are connected by boxlike structures which are squares with a side length close to the wavelength of blue light, about 500 nanometers.

These photos have taken us down to the microscale, the white bars in the last photo are a millionth of a meter, a micrometer, long.

To drop to the nano scale we must go 1000 times smaller.

One wavelength of blue light is as long as 5000 atoms placed side by side.

A single nanometer is as long as 10 atoms spaced side by side.

Scientific Explorations with Paul Doherty

© 2005

3 December 2005