The pine processionary is a moth of the subfamily Thaumetopoeinae in the family Notodontidae, known for the irritating hairs of its caterpillars, their processions, and the economic damage they cause in coniferous forests. The species was first described scientifically by Michael Denis and Ignaz Schiffermüller in 1775, though it was known to the ancients, with remedies described by Theophrastus, Dioscorides and Pliny the Elder. Its processionary behaviour was described in 1916 by the French entomologist Jean-Henri Fabre. It is one of the most destructive species to pines and cedars in Central Asia, North Africa and southern Europe.

The oak processionary (OPM) is a moth whose caterpillars can be found in oak forests, where they feed on oak leaves, causing significant damage. They travel in nose-to-tail processions, often arrow-headed, with a leader followed by rows of several caterpillars abreast. They are a human irritant because of their venomous setae, which can cause skin irritation and asthma. The species was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae.