Emerald ash borers (Agrilus planipennis) on a leaf. This beetle is native to Asia and eastern Russia, but is becoming an invasive species in Europe and North America. The female lays her eggs the bark of ash trees (Fraxinus sp.) 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.