Viruses were already infecting organisms some 300 million years ago, suggests a new study on what may be the oldest date yet for the emergence of an insect-infecting virus.

"This is the oldest date ever proposed for a virus," said study researcher Elisabeth Herniou, of the University of Tours in France.

"Knowing about ancient viruses can help us distinguish evolutionary processes resulting from historical interaction as opposed to adaptive processes happening in the present day," Herniou added in an email to LiveScience.

Waspy viruses

Viruses, which are packets of DNA in a protein shell, can't reproduce on their own and so must take over DNA and protein making machinery of a host in order to survive. To find out how old insect viruses are, researchers studied a virus that parasitic wasps use for their own good.

The wasps use their onboard viruses, called bracoviruses, to control the development and immunity of the caterpillars they parasitize. The wasps use the viral genes to make virus-like particles containing genes for a toxin, which they insert into their caterpillar prey when they lay their eggs.