The effect of hexaflumuron, a chitin synthesis inhibitor, on the mating success of three species of vector mosquitoes, namely Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi, was investigated. The three species were exposed to concentrations giving 5% and 50% inhibition of emergence (EI5 and EI50, respectively) at the fourth instar and to 0.005 and 0.05 mg/1 hexaflumuron at the pupal stage. Emergent adults were allowed to mate with each other and with their untreated counterparts. Reduction in mating (evaluated as % insemination) was highest in Ae. aegypti exposed at the larval stage. Mosquitoes exposed at the pupal stage to 0.05 mg/1 hexaflumuron showed higher reduction in mating than those exposed to 0.005 mg/1. The effect of hexaflumuron appeared to be cumulative, resulting in a 78–80% reduction in % insemination when treated males were mated with treated females, compared with untreated males mated with untreated females.
