Topical application of juvenile hormone (JH) and a juvenoid (ZR 515) to the crowded larvae of Cephonodes hylas caused pale pigmentation of the solitary phase at the next instar. This result suggests that the role of JH in the phase control of Cephonodes larvae and Locusta hoppers is similar or identical. JH I and JH II were 4-20 times more potent than JH III in their inhibition of dark pigmentation. ZR 515 was the most effective among the chemicals used.
