Round about now, in various US states, a vast swarm of cicadas will start crawling out of the ground. These black-bodied, red-eyed insects have stayed underground for 13 or 17 years, drinking from plant roots. When they greet daylight for the first time, they devote themselves to weeks of frenzied sex and cacophonous song, before dying en masse. They’ll be picked off by birds, snagged by squirrels, and crunched under shoes and tyres, but none of that will dent their astronomical numbers—which is perhaps the point of their lengthy underground stints, and their synchronous emergence.

But the cicada’s weird lifestyles have also left them with a different legacy. It involves the bacteria that live in their bodies, and it’s so weird