EFFECTS OF 2 INSECT GROWTH-REGULATORS ON ECDYSTEROID PRODUCTION IN AEDES-AEGYPTI (DIPTERA, CULICIDAE)

Diflubenzuron and OMS 2017 are insect growth regulators that affect la rval to adult development in Aedes aegypti (L.) by altering ecdysis. W hen larvae were exposed to sublethal concentrations, surviving adults express reduced reproductive potential. in mosquitoes, ecdysteroids ar e important in larval and adult ovarian development. We applied 30% em ergence reduction concentrations (EI(30)) of OMS 2017 and diflubenzuro n to 4th-instar Ae. aegypti to determine if changes in ecdysteroid pro duction may explain these physiological effects. Ecdysteroid concentra tions were measured in the larvae, pupae, and adults after treatment w ith both IGRs. After treatment with OMS 2017, the 1st peak of ecdyster oid production in larvae was totally inhibited, but after pupation, ec dysteroid concentrations were the same as in untreated controls. In di flubenzuron-treated larvae, the second peak of production was delayed and the ecdysteroid concentrations of the larvae, pupae, and adults we re depressed slightly when compared with untreated controls, The produ ction of ecdysteroids by the ovaries was not altered by sublethal larv al treatment with both IGRs. Although OMS 2017 and diflubenzuron belon g to the same chemical family, their mode of action apparently is diff erent.