Dual structural color mechanisms in a scarab beetle

Area of Science:

• * Structural coloration in animal cuticles.
• * Biomimetics and optical physics.
• * Insect morphology and iridescence.

Background:

• * Animal coloration often arises from pigments or structural mechanisms.
• * Structural colors, like iridescence, are produced by light interference with nanostructures.
• * Previous studies identified multilayer reflectors or diffraction gratings, but not both simultaneously in one species.

Purpose of the Study:

• * To investigate the dual mechanisms of structural color in *Mycterophallus* scarab cuticle.
• * To characterize the nanostructure responsible for red iridescence and rainbow iridescence.
• * To compare the optical properties and nanostructure with related scarab species.

Main Methods:

• * Light microscopy and spectrophotometry for optical property analysis.
• * Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for nanostructure visualization.
• * Comparative analysis with two related *Lomaptera* species.

Main Results:

• * *Mycterophallus* cuticle exhibits red iridescence via multilayer reflection and rainbow iridescence via a diffraction grating.
• * This represents the first documented instance of two independent structural color mechanisms in an animal.
• * Nanostructural parameters were correlated with observed optical properties, detailing the interaction of both mechanisms.

Conclusions:

• * The *Mycterophallus* cuticle utilizes a complex interplay of multilayer reflection and diffraction grating for its unique iridescence.
• * This finding expands our understanding of the diversity and evolution of structural coloration in insects.
• * The study provides a foundation for biomimetic applications inspired by this dual-mechanism system.