none The immature stages development of Microplitis tuberculifera (Wesmael) in the host's body of Mamestra brassicae was investigated during a dissertation about the biology of Microplitis tuberculifera (Wesmael). The larvae of Mamestra brassicae who damage the cabbage are parasitized from the Microplitis tuberculifera-females. The development of the parasitoid-egg and the first and second instar takes place in the body of the host. After the larva has left the host the cabbageworm dies. The eggs and the larval instars are illustrated microscopically.