Evolution often works like a tinkerer, repurposing old tools to build new traits. Butterfly wings are adorned with dazzling patterns: stripes, patches, and the iconic circular rings of color known as eyespots, which can deter predators or attract mates. But how do these intricate patterns arise? Do butterflies evolve entirely new genetic programs for each design, or do they cleverly repurpose existing ones?

Our recent study, published in Communications Biology, provides a surprising answer. The genes that originally shape the network of veins on insect wings, an ancient and essential trait, have been redeployed to form the colorful rings of butterfly eyespots. Around 400 million years ago, wing veins evolved through the establishment of sharp boundaries between different cells, orchestrated by a set of genes. Millions of years later, butterflies appear to have co-opted this same boundary-building machinery to separate the colored rings of eyespots.

To test this idea, we combined several cutting-edge approaches.

1) Laser microdissection allowed us to isolate tiny sections of developing wing tissue for RNA sequencing, revealing which genes were active in each region.

2) Fluorescent in situ hybridization and antibody staining mapped the spatial expression of these genes, and

3) CRISPR-Cas9 gene editing showed what happens when key genes are disrupted.

Our results confirmed that the genetic logic used to position wing veins has been reused in a new developmental context to generate eyespots. Rather than inventing new genetic instructions, butterflies rely on ancient developmental programs redeployed in novel ways.

This discovery adds to a growing list of examples showing how evolution innovates. New traits often arise not from entirely new gene networks, but from older ones being switched on in different contexts or at different times. This creative recycling of genetic toolkits has produced striking diversity from beetle horns to treehopper helmets, to the eye-like patterns on the wings of Bicyclus anynana.