When parasitic wasps come calling, some caterpillars have a surprising ally: a viral infection.
Insects called parasitoid wasps lay their eggs inside young moth larvae, turning the caterpillars into unwitting, destined-to-die incubators for possibly hundreds of wasp offspring. That’s bad news for viruses trying to use the caterpillars as replication factories. For the caterpillars, viral infections can be lethal, but their chances of survival are probably higher than if wasps choose them as a living nursery.
Now, a study shows how certain viruses can help caterpillars stymie parasitoid wasps. A group of proteins dubbed parasitoid killing factor, or PKF, that are found in some insect viruses are incredibly toxic to young parasitoid wasps, researchers report in the July 30 Science.
The new finding shows that viruses and caterpillars can come together to fight off a common wasp enemy, says study coauthor Madoka Nakai, an insect virologist at Tokyo University of Agriculture and Technology. A parasitoid wasp would kill a host that the virus needs to survive, so the virus fights for its home. “It’s very clever,” Nakai says.