  The wings of Lepidoptera contain a matrix of living cells whose function
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. Diverse scale
nanostructures and non-uniform cuticle thicknesses create a heterogeneous
distribution of radiative cooling that selectively reduces the temperature of
structures such as wing veins and androconial organs. These tissues are
supplied by circulatory, neural and tracheal systems throughout the adult
lifetime, indicating that the insect wing is a dynamic, living structure.
Behavioral assays show that butterflies use wings to sense visible and infrared
radiation, responding with specialized behaviors to prevent overheating of
their wings. Our work highlights the physiological importance of wing
temperature and how it is exquisitely regulated by structural and behavioral
adaptations.
