Decoding ladybird's colours: structural mechanisms of colour production and pigment modulation.

Abstract

This study investigates the mechanisms underlying colour production in the family Coccinellidae, focusing on two model species: A. bipunctata (L) and C. quatuordecimguttata (L). In this family, colours have traditionally been attributed primarily to pigments such as carotenoids and melanins. We propose an alternative perspective, considering the elytra as an integrated optical medium whose optical properties result from both its architectural design and the properties of its constituent materials, including matrix and pigments. In the present work, several methods were used, ranging from optical and electron microscopies, light-based techniques, to LC-HRMS analyses. Through local pigment analyses, microstructural examination of elytra, and modelling of interaction of elytra with light, we show that, while pigments are central to patterning and contribute to colour, overall colour also results from one or more physical mechanisms that may operate simultaneously. In the light of these results, we assume that the complex and diverse colouration in the Coccinellidae can only be elucidated by considering the interplay of pigments and the optical properties of the elytron cuticle.