A polydnavirus /pɒˈlɪdnəvaɪrəs/ (PDV) is a member of the family Polydnaviridae of insect viruses. There are two genera in the family: Bracovirus and Ichnovirus. Polydnaviruses form a symbiotic relationship with parasitoid wasps; (ichnoviruses (IV) occur in ichneumonid wasps and bracoviruses (BV) in braconid wasps). The larvae of wasps in both of those groups are themselves parasitic on Lepidoptera (moths and butterflies), and the polydnaviruses are important in circumventing the immune response of their parasitized hosts. Little or no sequence homology exists between BV and IV, suggesting that the two genera have been evolving independently for a long time.