Periodical cicada broods famously come out of hiding for a few weeks in spring to shed their skin, eat, mate and die—while ruining a few summer weddings and enlivening some barbecues along the way. During this time, they lay their own eggs, and the 13- or 17-year cycle starts again.
After years of living beneath the soil teenage cicadas, wiggle up through the soil, as Anna Rothschild explains in the PBS Digital Studios video above. In that soil, spores of a gnarly fungus Massospora cicadina lies waiting for them. The spores infect the cicada’s abdomen and spreads like an STD as the bugs mate.
Eventually, the fungus splits the bug’s abdomen, and its butt falls off, as Rothschild put it. Despite the gruesome image, cicadas don’t seem too bothered by it, continuing about their short existence as if losing your butt is totally normal. Perhaps that’s no surprise, since Rothschild says the bizarre fungus actually poses less of threat to periodical cicada survival than predators or habitat destruction.