Interactions between adults of some species of Netelia Gray (Hymenoptera: Ichneumonidae: Tryphoninae) and their caterpillar hosts (Lepidoptera)

Abstract

• Five species from three subgenera of Netelia were observed ovipositing on their hosts under laboratory conditions. Two species of the subgenus Bessobates oviposited without a separate insertion of the ovipositor beforehand. One species of the subgenus Netelia and two of the sub- genus Paropheltes employed a venom causing weak (often incomplete) temporary paralysis, ad- ministered as a separate action prior to oviposition. The venoms had no long-term adverse effect on hosts and it appears that these taxa, and perhaps all other groups of ectoparasitic koinobiont Ichneumonidae, lack the host-regulating venom systems that have been regarded as instrumental in the evolution of endoparasitism in some koinobiont cyclostome Braconidae. In all species sub- stantial parasitoid development was delayed until the final instar host had constructed its pu- pation site, wherein it was overwhelmed as a prepupa. Species of all three subgenera dumped eggs in the absence of hosts, and (if kept humid) such eggs subsequently split to reveal a living first instar larva (but not investigated in the subgenus Paropheltes). Species of all three subgenera indulged in non-destructive concurrent host-feeding, despite being supplied with honey solution ad libitum, making the necessary wounds on the host's body with their mandibles. Occasionally non-destructive host-feeding occurred on hosts that were not also being parasitised.