EFFECTS OF THE JUVENILE-HORMONE MIMIC PYRIPROXYFEN ON EGG DEVELOPMENT, EMBRYOGENESIS, LARVAL DEVELOPMENT, AND METAMORPHOSIS IN THE DESERT LOCUST SCHISTOCERCA-GREGARIA (ORTHOPTERA, ACRIDIDAE)

The juvenile hormone mimic pyriproxyfen disrupted embryogenesis when a pplied topically to eggs of the desert locust Schistocerca gregaria Fo rskal. Eggs treated on days 3-6 were inhibited at various stages of de velopment, depending on dose and age. In particular, 0.001-0.01 mu g b locked development of 3- and 4-d-old eggs at blastokinesis. Treatment of 7- to 11-d-old eggs was ineffective up to 10 mu g. Insects that hat ched successfully failed to display any postembryonic defects. Topical application of the mimic to females had a small ovicidal effect. The metamorphic molt was disrupted when the mimic was applied topically to 5th-instar S. gregaria. Insects retained characteristics of the 5th i nstar and in extreme cases supernumerary 5th instars were formed. Addi tional defects included essentially normal adults that were malformed and could not fly. Oral doses were considerably less effective. Applic ation to 4th-instar nymphs did not produce supernumerary characteristi cs in postecdysial insects, though a large proportion of insects showe d abnormalities when they reached adult, which in some cases prevented night. Topical application of the mimic to 5th instar affected the le ngth of the instar. The effects depended on dose and day of treatment.