Insect growth disruptors of the aryl terpenoid ether type including 185 compounds derived from 10 basic olefinic, epoxidised and alkoxidised type-structures were tested against the prepupae of the Mediterranean brocade, Spodoptera littoralis. The potent decenyl compounds are mainly derivatives of 4,8-dimethyl-3,7-decadiene and the epoxides of its external olefinic bond. The potent nonenyl compounds are mainly derivatives of either 4,8-dimethyl-3,7-nonadiene and the epoxides of its external olefinic bond or 3,7-dimethyl 6,7-epoxy-2-nonene. The phenyl group of the potent compounds have either methylenedioxy (3,4-), ethyl or methyl groups (4- or 3-). The presence of an alkoxy group on the terpenoid side chain, and/or the phenyl group does not lead to formation of a potent compound. The addition of one terminal carbon atom to some nonenyl derivatives leads to activity in the resulting decenyl compound. Continuing studies on synthetic juvenile hormone analogues may provide novel potent compounds for more benign insect control strategies.