Research Article

Structural colour and photonic mechanisms in the blow flies Calliphora vicina and Lucilia richardsi (Diptera: Calliphoridae)

¹ Department of Physics & Namur Institute of Structured Matter (NISM), University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur, Belgium
² Département de Physique, École Normale Supérieure de Lyon/Université Claude Bernard Lyon 1, 46 Allée d’Italie, 69364 Lyon Cedex 07, France
³ Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom
⁴ Institute of Life, Earth and Environment (ILEE), University of Namur (UNamur), Rue de Bruxelles 61, 5000 Namur, Belgium
⁵ Micro- and Nanophotonic Materials Group & Research Institute for Materials Science and Engineering, University of Mons, Place du Parc 20, 7000 Mons, Belgium

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 23 September 2025
Accepted: 3 December 2025

Abstract

Structural colours in natural organisms are created by complex photonic architectures giving rise to remarkable visual appearances. In arthropods, these structures are usually made of biopolymers and comprise photonic crystals. They are often iridescent, i.e., their colours depend on the incidence and observation angles. Despite the interest of the scientific community in a large variety of species including those belonging to butterflies and beetles, some orders such as dipterans have been overlooked so far. In this work, the structural colours from the abdomens of two dipteran species, namely Calliphora vicina and Lucilia richardsi blow flies, with different displayed colours were investigated by spectrophotometry and optical simulations. Using electron microscopy, we identified multilayer photonic structures as the primary mechanism responsible for their visual appearances, with possible additional thin-film interference in C. vicina. In addition, the dipterans’ colours were analysed in terms of chromaticity as well as with respect to the visual sensitivities of the species and the ones of some of their predators. The reflectance spectra of the blow flies investigated were found to correlate with high absorption by their own and their predators’ photoreceptors. These findings indicate that structural colouration in blow flies may influence not only communication with conspecifics but also interactions with predators.