Autumn leaves falling from the cottonwoods that line the banks of the San Pedro River sometimes exhibit these fascinating patterns. They are the tracings of insect larvae collectively called “leaf miners.” Leaf mining is a type of behavior that involves larvae that live within a leaf, feeding on the inner tissues while leaving the epidermal (outer) layers of the leaf intact. This affords the larvae some measure of protection from predation. Leaf mining evolved in several different families of insects, including flies, beetles, and moths.