none Heliothis virescens (F.) larvae that were parasitized by Microplitis demolitor Wilkinson or by M. croceipes (Cresson) consumed significantly less artificial diet than unparasitized larvae. The greater proportion of feeding by unparasitized larvae occurred after they reached the fourth instar, whereas feeding by parasitized larvae remained at a low level. Results indicated that larvae parasitized before reaching the fifth instar by either Microplitis spp. may cause considerably less damage to the host plant than unparasitized larvae. The fifth instar apparently is suitable only for development of M. croceipes .