The Polydnaviruses (PDV) are a family of insect viruses that contain two genera: Ichnoviruses (IV) and Bracoviruses (BV). The ichnoviruses occur in ichneumonid wasps and bracoviruses in braconid wasps. The virus is composed of multiple segments of double-stranded superhelical DNA packaged in capsid proteins and a double layer or single layer envelope.
The full genome of the virus is integrated into the genome of the wasps and the virus only replicates in specific cells in the female wasp’s reproductive system. The virus is injected with the wasp egg into the body cavity of a host caterpillar. The virus then affects the caterpillar’s immune system which allows for the wasp egg to mature inside the caterpillar.
It is believed that the virus was either derived from was genes or that previous wasps developed a relationship with a virus that led to integration of the virus into the wasp’s genome.