Emerald ash borer (Agrilus planipennis) tracks on a green ash tree (Fraxinus pennsylvanica) killed by the insect. The emerald ash borer is native to Asia and eastern Russia, but is becoming an invasive species in Europe and North America. The female lays her eggs in the bark of ash trees and the larvae burrow through the bark to feed on the phloem tissue and sapwood underneath. Groups of larvae can cause significant damage to a tree, disrupting the flow of nutrients, and eventually leading to its death. Photographed in Detroit, Michigan, USA.