Laboratory evaluation of Alsystin, a chitin synthesis inhibitor, against Culex pipiens pipiens L. (Dip., Culicidae): effects on development and cuticle secretion

Alsystin, a benzoylphenylurea derivative, was evaluated on Culex pipiens pi piens 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 mortal ity recorded for the other later developmental stages. Treatment resulted i n a dose-dependent reduction in adult emergence. Moreover, treatment caused morphological aberrations depending upon the importance of larval-adult tr ansformation and significantly increased the duration of both third and fou rth larval instars. A histological study conducted on fourth instar larval integument, revealed that Alsystin delayed the ecdysis and significantly re duced the thickness of both larval and pupal cuticles secreted compared wit h controls. Moreover, the apolysis that occurred at day 4 in controls was n ot affected by treatment.