Transmission of a nuclear polyhedrosis virus (NPV) from generation to generation was studied in Mythimna separata (Walker). NPV infected adults were produced by feeding 6th instar larvae with subnormal concentration of NPV. Egg and larval mortality was observed in the progeny from infected adults as the transmission being transovum and transovarial. The healthy adults were able to transmit more NPV to their progeny by egg surface coating when fed with NPV orally. When both sexes were fed, the larval mortality in the first instar was more in the case of eggs laid on the first day (19.68%) and declined in the case of second (16.64%) and third day laid eggs (11.34%)