Supplementary table from: Spectrometry of Greta oto untreated and hexane treated clear wing regions and simulated reflectance spectra

The wings of butterflies and moths (Lepidoptera) are typically covered
with thousands of flat, overlapping scales that endow the wings with
colorful patterns. Yet, numerous species of Lepidoptera have evolved
highly transparent wings, which often possess scales of altered morphology
and reduced size, and the presence of membrane surface nanostructures that
dramatically reduce reflection. Optical properties and anti-reflective
nanostructures have been characterized for several ‘clearwing’
Lepidoptera, but the developmental processes underlying wing transparency
are unknown. Here, we apply confocal and electron microscopy to create a
developmental time-series in the glasswing butterfly, Greta oto, comparing
transparent and non-transparent wing regions. We find that during early
wing development, scale precursor cell density is reduced in transparent
regions, and cytoskeletal organization during scale growth differs between
thin, bristle-like scale morphologies within transparent regions and flat,
round scale morphologies within opaque regions. Next, we show that
nanostructures on the wing membrane surface are composed of two layers: a
lower layer of regularly arranged nipple-like nanostructures, and an upper
layer of irregularly arranged wax-based nanopillars composed predominantly
of long-chain n-alkanes. By chemically removing wax-based nanopillars,
along with optical spectroscopy and analytical simulations, we demonstrate
their role in generating anti-reflective properties. These findings
provide insight into morphogenesis and composition of naturally organized
micro- and nanostructures and may provide bioinspiration for new
anti-reflective materials.