A three-year period of observations, collecting, and recording data on cocoons ofRothschildia aromaSchaus showed that parasitism is still high enough (63.1 percent) in areas free of insecticide applications to account for an undisturbed natural balance, with moth survival only 11.4 percent. In contrast, in areas where intense and continuous applications have been going on for the past ten years, the percentages have been practically reversed, parasitism reaching only 18.1 percent and moth survival 68.4 percent. Emphasis is made on this previously cryptic case of natural biological control and others that may have been or are being disrupted in EI Salvador and other countries in Central America. It is suggested that insecticides should be judiciously employed to conserve the beneficial insects.