This paper deals with the biology and ecology of Microplitis prodeniae (Viereck), a dominant braconid wasp parasited on Spodoptera litura Fabricius, one of the most important pests in tobacco fields. The wasp has two climaxes on population dynamics, one of which occurs at the last ten day of April and the other occurs at the mid-ten day of June, which can control its host in some degree. It emerges normally all day long at 24~28℃ and 75%~85% RH. But the emergence chiefly occurs at 4~6 am. The quantity of fe...