No abstract

Diflubenzuron, topically applied (0·5 μg insect−‐1) to Cydia pomonella (L.) at pupal ecdysis disturbed growth and development of oocytes. It delayed the adult ecdysis and caused a decrease in both thickness of the follicular epithelium and the size of the basal oocyte during the pupal development. On the other hand, the size of basal oocytes, the protein content per ovary and the number of oocytes per ovary recorded in newly emerged adults were significantly reduced after diflubenzuron treatment. These results, together with observations in several other species, indicate that the reduction in fecundity and egg viability is probably due to interference of diflubenzuron with the vitellogenesis process.

When fed to adults of Tenebrio molitor, diflubenzuron reduced the longevity, the weight of the adults and the thickness of the post‐ecdysial adult cuticle. It also affected the production of the peritrophic membrane. The loss of weight and the decrease of longevity of the treated adults may have been because of alterations to the peritrophic membrane, caused by the inhibition of chitin biosynthesis by diflubenzuron.

Alsystin, a benzoylphenylurea derivative, was evaluated on Culex pipiens pipiens L. Treatment was made on newly third‐ and fourth‐instar larvae for 24 h. Mortality occurred at various developmental stages following treatment. However, death as larvae was relatively important compared with the mortality recorded for the other later developmental stages. Treatment resulted in a dose‐dependent reduction in adult emergence. Moreover, treatment caused morphological aberrations depending upon the importance of larval–adult transformation and significantly increased the duration of both third and fourth larval instars. A histological study conducted on fourth instar larval integument, revealed that Alsystin delayed the ecdysis and significantly reduced the thickness of both larval and pupal cuticles secreted compared with controls. Moreover, the apolysis that occurred at day 4 in controls was not affected by treatment.

No abstract