Erora opisena optical and tomography data and associated MATLAB scripts

Biophotonic nanostructures in butterfly wing scales remain fascinating
examples of biological functional materials, with intriguing open
questions regarding formation and evolutionary function. One particularly
interesting butterfly species, Erora opisena (Lycaenidae: Theclinae),
develops wing scales that contain three-dimensional photonic crystals that
closely resemble a single gyroid geometry. Unlike most other
gyroid-forming butterflies, E. opisena develops discrete gyroid
crystallites with a pronounced size gradient hinting at a developmental
sequence frozen in time. Here, we present a novel application of a
hyperspectral (wavelength-resolved) microscopy technique to investigate
the ultrastructural organisation of these gyroid crystallites in dry,
adult wing scales. We show that reflectance corresponds to crystallite
size, where larger crystallites reflect green wavelengths more intensely;
this relationship could be used to infer size from the optical signal. We
further successfully resolve the red-shifted reflectance signal from wing
scales immersed in refractive index liquids with varying refractive index,
including values similar to water or cytosol. Such photonic crystals with
lower refractive index contrast may be similar to the hypothesized
nanostructural forms in the developing butterfly scales. The ability to
resolve these fainter signals hints at the potential of this facile light
microscopy method for in vivo analysis of nanostructure
formation in developing butterflies.