none Time between oviposition and ingestion of nuclear polyhedral virus (NPV) (570, 40 and 20 polyhedral inclusion bodies per mm super(2) of diet surface) was found to be critical in the emergence of Microplitis croceipes (Cresson) from NPV-infected third-instar Heliothis virescens (Fab.). Parasitoid emergence was significantly reduced in host larvae exposed to NPV up to 3 days after oviposition at 26 degree C.