Scheme of terpene-mediated interactions of a maize seedling above and below ground. Damage of maize leaves by lepidopteran herbivores activates the terpene synthases TPS10 and TPS23, which produce a blend of volatile terpenes. This blend attracts several species of parasitic wasps. Damage of the roots by D. v. virgifera activates the terpene synthase TPS23. The volatile terpene produced by TPS23, (E)-β-caryophyllene, attracts entomopathogenic nematodes. Drawings by Tobias G. Köllner.