Larvae of the leafbeetlesPhaedon amoraciae, Phaedon cochleariae, Gastrophysa viridula, and Plagiodera versicolora biosynthesize the two iridoids chrysomelidial 1 and/or plagiodial 3 from geraniol 7 by an oxidative sequence related to that known from plants en route to the iridane skeleton. Following ω-oxidation of geraniol 7 the resulting 8-hydroxygeraniol 8 is oxidized further to 8-oxocitral 9.