Coloring by Structure

Luna Shyr for National Geographic (published 16 January 2011)
Photography by Martin Oeggerli, with Marco Cantoni EPFL

The majority of butterfly colors are pigmentary. However, scientists have now found out that vibrant green wing colors can also be induced by complex three dimensional crystals – called gyroids (see porous red patches underneath corrucated green scale surface).

The gyroid network forms during the butterflies’ cocoon phase and refracts light in the adult insect’s wing. Since the structure measures only a few hundred nanometers it remains difficult to document.

In collaboration with Marco Cantoni from the ‘Ecole Polytechnique Federale De Lausanne’, Micronaut has explored the gyroid arrangement in the wing of Parides sesostris, the Emerald-patched Cattleheart Butterfly.

The resultant image shows a cross-section through a single wing scale and has been produced with a ‘Focused-ion beam’ (FIB) electron microscope. The technology uses a beam of focused ions to manipulate the microscopically small sample and the instrument is usually applied in material investigations. Similar to the ‘Scanning-Electron-Microscopes’ (SEM), the FIB also allows investigations with extremely powerful magnification.

Original post accessible at: Coloring by Structure, National Geographic Blog Central, 16 January 2011