Obligatory multiparasitism in the tussock moth,Orgyia leucostigma

Orgyia leucostigmahaemocytes were able to encapsulate and destroy eggs ofHyposoterspecies, thereby preventing successful parasitism. When host larvae had previously been parasitized byCotesia melanoscela, however, this response was not observed, and 3 differentHyposoterspecies could be reared to maturity in the normally non-permissive host. Appropriate injection experiments established thatC. melanoscelavirus and venom were both required in order for successful parasitism byHyposoterto occur. Covalent cross-linking ofC. melanoscelaviral DNA led to an immune response againstHyposoterlarvae, but not eggs, suggesting that an active viral genome may be required for complete development ofHyposoterspecies in tussock moth larvae.