Three aromatic juvenoids were evaluated for morphogenetic activity on Schistocerca americana. Fenoxycarb, the most active insect growth regulator examined, was found to induce a significant mortality in developing fifth stage nymphs and caused severe morphogenetic damage during ecdysis to the adult. Juvenoid treatments were also observed to increase the duration of the last nymphal stage and to induce chromotropic colour changes similar to that observed in the solitary phase of the desert locust, Schistocerca gregaria Forskal.