Japanese cicadas are infested with an insect-eating fungus, but the invader is actually keeping them alive, The Atlantic reports. The bugs typically rely on a bacterium called Hodgkinia in their blood that provides them with essential vitamins and nutrients missing from their diet of plant sap. But if Hodgkinia’s tendency to disintegrate and split into daughter species, which cannot survive on their own, continues, they run the risk of becoming too small to function or disappearing all together. Luckily, the Ophiocordyceps fungus, which has also taken up residence in cicadas, performs the same nutritional functions, researchers report this week in the Proceedings of the National Academy of Sciences. Though it usually kills insects, it doesn’t in this case because the version that infects cicadas is mutated and weaker. As a result, the parasite has the potential to save cicadas from extinction, scientists say.