The biological and histological effect of insect growth regulator (flufenoxuron) evaluated on 2^nd larval instar of Agrotis ipsilon as a chitin synthesis inhibitor. The effect of sublethal dose LC₅₀ was used to investigate its effect on some developmental and reproductive parameters of Agrotis ipsilon that survived treatment of newly molted second instars. Results indicated that the flufenoxuron significantly enhanced the mean larval and pupal durations, whereas they significantly declined the mean percentage pupation, adult emergence, adult longevity, fecundity, and fertility compared to untreated insects. Also, our studies recorded many histological aberrations to the ovary of Agrotis ipsilon female moth.