Eleven years ago, while studying the microbes that live in water-filled rock fractures in South African gold mines, geomicrobiologist Tullis Onstott of Princeton University noticed wormlike organisms living in cultures taken from 1.3 kilometers below the surface. “Well, I’m not a worm kind of guy,” Onstott says. So he contacted Gaetan Borgonie, a nematologist at Ghent University in Belgium, who collected and filtered tens of thousands of liters of water samples from five mines in the area to find the rare creatures, which belong to the worm group called nematodes. In addition to some previously described nematodes, which scientists had never before seen living at this extreme depth, the researchers discovered a new species of nematode that subsists on microbes and requires only trace amounts of oxygen. They named the deep-living, heat-loving species Halicephalobus mephisto. The name refers to Faust’s devil, Mephistopheles, and means “he who loves not the light” in Greek.