A historical viral infection gave some insects genes that allow them to parasitise their caterpillar hosts, a new study finds.
Many species of wasps lay their eggs inside caterpillars. To make this possible, the wasps' have a secret weapon in the form of a dose of virus-like particles that are injected along with the eggs.
Not only do these disable the caterpillars' immune system to stop it attacking the eggs, they also cause paralysis and keep the host from pupating – turning the caterpillar into an eternally youthful larder and nursery for the wasp grubs.
A closer look at these particles reveals that, although they look like viruses, they contain genetic material from the wasp, which is transcribed into the caterpillars' DNA – causing production of the very toxins that bring about their downfall.
That's just an unspeakably cool discovery!