Every day we get more proof that wasps are the most terrifying creatures on the planet. Not only do they mind-control caterpillars and inject them with their wasp babies, they also managed to enslave a virus to do their dirty work for them.
Just when you get used to wasps, they spring some new diabolical thing on you. When you get accustomed to the fact that they stuff other creatures full of their eggs so that their larvae eat the other creature from the inside out, it is revealed that they also dabbled in mind control. And when you finally settle down about the fact that the wasps can drive caterpillars around like golf carts, the wasps add a virus to the mix.
When you think about it, the use of a virus makes sense. There's a reason why every single thing that gets under our skin doesn't fester or proliferate until it takes over our entire body. We have an immune system that attacks debris and breaks it down. Caterpillars have the same thing, until these viruses, called polydnaviruses hit them. The viruses are injected along with the wasp egg. The virus takes out the caterpillars' immune systems so the wasp eggs aren't in danger.
What exactly is this virus? Where did it come from and is it an opportunistic hitchhiker or another subjugated creature? Given the history and character of the wasp, it's no surprise that a study of the ovaries of wasps and the DNA of the virus indicates that the virus is under subjugation. The virus was, a long time ago, a type of nudivirus - a group of viruses that tend to attack the reproductive system. It didn't know what it was getting into when it went after a wasp. Now its DNA is reproduced inside a special part of the wasp ovary. It doesn't replicate inside its host. It can't even make its own protein coat. Essentially, scientists believe that it has become part of the wasp. The virus infected the insect, and the insect ripped it apart and used its pieces to reproduce.
That's wasps for you.
[Via Viral DNA Deliver's Wasp's Sting, Evolution of Polydnaviruses.]