Where did the wasp’s sting come from?

If you've ever been on the wrong end of a wasp's sting, you'll know how painful it is. But did you know that the paralysing chemicals that some parasitic wasps use to stun their hosts came from virus genes that the wasps picked up around 100 million years ago. This new finding answers the conundrum of where they came from.

This research, by Annie Bezier and her colleagues in France and Switzerland, was done using braconid wasps, that prey on other insects, laying their eggs in caterpillars and other larvae. These wasps use paralysing proteins to immobilise their hosts, providing a nice home for the growing wasp grubs.

Back in 1967, scientists noticed that virus-like particles were present in the ovaries of female braconid wasps, and that these were injected into the host when eggs were laid. It's thought that the virus particles help to suppress any immune response in the host caterpillar, which might cause it to reject the wasp grub.

These virus particles were found to combine with DNA to make viruses known as poly-DNA viruses.  But when these virus-like particles were found in many different types of wasp it posed a problem. Where were these viruses coming from - and were they actually viruses as all?

Bezier and her team found that the genes encoding these virus-like particles were related to an ancient type of virus called a nudivirus. But the virus-like protein packages didn't carry virus DNA, as you might expect, but wasp DNA. So the wasp DNA has somehow got mixed up with the virus DNA. And now the virus-like proteins are used to transmit wasp DNA into the parasite's host.

Well it sheds new light on the relationship between viruses and their hosts, as well as the relationship between these parasitic wasps and their hosts.