Some tropical butterflies live surprisingly long lives. Is it their high-protein diet?

Whereas most adult butterflies rely entirely on sugary nectar to fuel them, butterflies in the _Heliconius_ genus have evolved to also eat pollen. Pictured here is an Agraulis vanillae. (Wikimedia Commons/ Christina Butler), CC BY Butterflies are charismatic, colourful and cherished around the world. One of the most diverse groups of insects, with more than 19,000 described species, they inspire international organizations such as the North American Butterfly Association and the Xerces Society,…