The dynamics of corn earworm infection with Hyposoter didymator were studied on cotton plants in the Azerbaijan SSR, USSR. The parasites is most effective at the beginning of the season and in years with decreased spring-early summer temperatures. The seasonal development of the parasite is regulated by the temperature, whose reduction below the optimal level inhibits the parasite's activity thus providing the state of rest. Data were presented on the effect of temperature, photoperiod and age of the host's infection on the developmental and survival rate, and fecundity of Hyposoter didymator. The optimal regimes of mass breeding of Hyposoter were determined. none