UC Berkeley

The coloration of butterflies and moths, Lepidoptera, has been an important force in biological inquiry, providing among the first supporting evidence for biogeography, Darwinian evolution, and models of morphogen diffusion. In nature, color patterns have evolved that aid species’ navigation of many ecological interactions via crypsis, warning coloration, mate signaling, and the multiple forms of mimicry, which often lean heavily upon color to achieve their effect.

Butterflies and moths as a whole have evolved the ability to produce all of the colors visible by humans, as well as into the UV range. As is true for most animals, the repertoire of pigments available for use in Lepidoptera is actually rather restricted – by and large limited to long-wavelength colors red, orange, and yellow, as well as, black and brown pigments. To expand into the short wavelength (violet, blue and green), Leps have repeatedly resorted to manufacturing photonically-active nanostructures. These harness physical properties of light to create the impression of color in an observer without having to manufacture a pigment. Despite knowledge of butterfly structural coloration for centuries, intense study has only taken off following the advent of the electron microscope, and despite interest, studies have been largely limited to descriptive studies and physical estimations of their function.

I have undertaken efforts to understand the developmental and cellular underpinnings of structural coloration in butterflies. In the work presented here I have furthered the understanding of the field with a particular focus on how pigments modulate the diverse structural colors of 2 genera – the Morpho genus of the neotropics and the Achillides sub-genus of Papilio found throughout Oceania, East, and South Asia. In addition, I have addressed how scale ultrastructure is constructed in the developing pupa from a cell biological perspective. These studies have come hand-in-hand with the improvement of live-imaging techniques, which I argue, will be indispensable for future studies on scale development. What has emerged, is the suggestion that the Actin cytoskeleton, is essential for ultrastructural formation of scales including the modulation of nanostructure profiles. What’s more, I have shown that melanin is deployed to tune the saturation of structural color reflections and, in at least one case, to tune the hue of a multilayer-based structural color.