A fungus called Massospora, which can produce compounds of cathinone — an amphetamine — infects a small number of them and makes them lose control. The fungus takes over their bodies, causing them to lose their lower abdomen and genitals. And it pushes their mating into hyperdrive. "This is stranger than fiction," Matt Kasson, an associate professor of forest pathology and mycology at West Virginia University, tells NPR's All Things Considered. "To have something that's being manipulated by a fungus, to be hypersexual and to have prolonged stamina and just mate like crazy."