Beat the Heat in the Living Wings of Butterflies

The wings of Lepidoptera contain a matrix of living cells whose functioning requires appropriate temperatures. However, given their small thermal capacity, wings can overheat rapidly in the sun. Here we analyze butterfly wings across a wide range of simulated environmental conditions, and find that regions containing living cells are maintained at cooler temperatures in a manner that is largely unaffected by visible color patterns. Diverse scale nanostructures and non-uniform cuticle thicknesses create a heterogeneous distribution of radiative cooling that selectively reduces the temperature of living structures such as wing veins and androconial organs.