# Trade-offs in insect eye nanocoatings: implications for vision, ecology, and climate sensitivity

## TL;DR

Fireflies have temperature-sensitive eye coatings that improve vision but limit their habitat range, linking nanoscale structures to ecological adaptation.

## Contribution

First thermodynamic analysis of temperature-sensitive nanocoatings in fireflies, linking nanostructure self-assembly to ecological constraints.

## Key findings

- Temperature-sensitive nanocoatings in Luciola fireflies form only within a narrow thermal range, limiting habitat expansion.
- Firefly nanocoatings follow a trade-off, allowing only two of three properties: anti-reflectivity, self-cleaning, or thermo-insensitive formation.
- Sexual dimorphism in fireflies resolves the nanocoating trade-off, with males and females favoring different functional properties.

## Abstract

Functional traits shape ecological niches, yet the interplay between nanoscale structural modifications, sexual dimorphism, and habitat range remains poorly understood. In fireflies, cuticular nanostructures that enhance bioluminescent signaling efficiency also impose ecological constraints. Anti-reflective nanocoatings improve cuticle transparency and optical performance but typically increase surface adhesion, reducing fitness. In Luciola lusitanica, this trade-off is mitigated by temperature-sensitive nanocoatings that form only within a narrow thermal range, limiting habitat expansion. This study presents the first thermodynamic analysis of environmentally constrained nanocoating formation, demonstrating how small temperature fluctuations can destabilize protein-lipid self-assembly. These findings link nanoscale biophysics to ecological resilience, providing a framework to understand how the environmental sensitivity of structural self-organization shapes adaptation, species distribution, and evolutionary potential.

Temperature-sensitive firefly nanocoatings reveal how nanoscale self-assembly may link optical and self-cleaning functions to ecological range. Thermodynamic limits on nanostructure formation can contribute to adaptation, behavior, and species distribution.

Corneal nanocoatings form the first layer of the insect cuticle, and defects in their assembly disrupt cuticle formation.These nanocoatings follow a functional trade-off: insects can realise only two of three properties: anti-reflectivity, self-cleaning, or thermo-insensitive formation.Most fireflies resolve this trade-off through sexual dimorphism, with males favoring anti-reflectivity and females self-cleaning, both supported by thermally robust assembly.Luciola fireflies combine anti-reflective and anti-wetting nanocoatings, but this advantage comes at the cost of a narrower environmentally viable habitat range.

Corneal nanocoatings form the first layer of the insect cuticle, and defects in their assembly disrupt cuticle formation.

These nanocoatings follow a functional trade-off: insects can realise only two of three properties: anti-reflectivity, self-cleaning, or thermo-insensitive formation.

Most fireflies resolve this trade-off through sexual dimorphism, with males favoring anti-reflectivity and females self-cleaning, both supported by thermally robust assembly.

Luciola fireflies combine anti-reflective and anti-wetting nanocoatings, but this advantage comes at the cost of a narrower environmentally viable habitat range.

Temperature-sensitive firefly nanocoatings reveal how nanoscale self-assembly may link optical and self-cleaning functions to ecological range. Thermodynamic limits on nanostructure formation can contribute to adaptation, behavior, and species distribution.