Juvenoids, applied topically on larvae of Corcyra cephalonica harbouring the larvae of the parasitoid, produce various types of developmental derangements in parasitoid C. blackburni. The deformed morphs, e.g., apparently normal adults, adultoids and prolonged larvae were developed at different rates by different doses of juvenoids. Larval and pupal mortality rates of the parasite were 6-13 and 4-8% respectively in different treatments. Deformities in reproductive system of the parasitoid were increased or decreased ovariole number, development of compound egg chamber and ill-developed ovariole. none