Ladybird’s colouration depends on structure and not only on pigments

June 26, 2025

The colouration of ladybirds has traditionally been attributed exclusively to the presence of pigments such as carotenoids and melanin. This study reveals that the micro- and nanoscale architecture of the elytra can selectively reflect certain wavelengths of light, thereby contributing to the perceived colour. This discovery of a structural contribution to the colour of ladybirds has opened up new perspectives in evolutionary biology and in the interpretation of colour-related signals.

This study, which was recently published in the interdisciplinary journal PLOS ONE and was the subject of a Highlight in the same journal, contradicts the notion that the colouration of ladybirds (Coccinellidae) is solely the result of pigments such as carotenoids or melanins. Using the species Adalia bipunctata (L.) and Calvia quatuordecimguttata (L.) as models, the researchers demonstrated that the microstructure of the elytra also contributes to colour production.

The study was conducted by a multidisciplinary team composed of physicists from the NeO group at CEMES, ecologists from CRBE, and chemists of natural substances from the PHARMA-DEV laboratory. It combines approaches based on optics, transmission electron microscopy, and numerical simulations to model the light interaction with the elytra microarchitecture. The results reveal that the structure selects certain wavelengths, generating specific colours. Two physical mechanisms were identified: interference by chirped multilayers in the exocuticle and incoherent scattering by micrometric concavities on the surface.

In parallel, the pigments were studied on a local scale using Raman spectroscopy, supplemented by ultra-high-performance liquid chromatography–high-resolution mass spectrometry (UHPLC-HRMS) analysis and metabolomic approaches. These methods were employed to identify specific pigments and highlight significant variations in the chemical composition of the elytra of the two species. These differences influence their optical properties and contribute to the diversity of colouration.

These results suggest that elytra should be considered as complex optical media where the architecture and the optical properties of the elytra’s constituent materials — the matrix and pigments — interact to produce the perceived colouration. This integrative approach provides a new framework for understanding the chromatic diversity of ladybirds and its potential role in ecological signalling. The study also emphasises the importance of combining genetic analyses with the study of integumentary structures in evolutionary ecology, rather than focusing solely on pigments.

Contact:
Marzia Carrada | marzia.carrada[at]cemes.fr

Publication:
Decoding ladybird’s colours: Structural mechanisms of colour production and pigment modulation
M. Carrada, M. Haddad, L. M. San-Jose, G. Agez, J.-M. Poumirol, and A. Magro
PLOS ONE 20(6) (2025) e032464
DOI: https://doi.org/10.1371/journal.pone.0324641