Temporal Synchronization of Emergence of Hyposoter exiguae and H. fugitivus (Hymenoptera: Ichneumonidae) with Apolysis Preceding Larval Molting in Manduca sexta (Lepidoptera: Sphingidae)

Abstract

Hyposoter exiguae (Viereck) is an ichneumon wasp parasite of many species of lepidopteran larvae including the tobacco hornworm. After parasitization of first-instar Manduca sexta (L.), wasp larvae developed inside the host and emerged during the host's second or third instar, after it had undergone apolysis in preparation for larval molting. When the host was parasitized as late as the third instar, emergence was delayed until onset of host apolysis preceding the fourth or fifth instar. Fourth-instar M. sexta larvae were not successfully parasitized by H. exiguae, due to parasite encapsulation and developmental disruption of the host. In hosts with emerging wasps, size of the emerging parasite was correlated with size of the host's head capsule, indicating that larger parasites emerged from larger hosts. Experiments with H. fugitivus (Say) demonstrated that it also emerged from tobacco hornworm larvae undergoing apolysis preceding larval molting, suggesting that other species of Hyposoter may show a similar developmental interaction with their host.