Wetanema sp. is a nematode parasite of the hind gut of the freezing-tolerant orthopteran Hemideina maori (a New Zealand alpine weta). The prevalence and intensity of infection remains high throughout the winter, suggesting that the parasite can survive despite the regular freezing of the host. In the laboratory, Wetanema has survived freezing within its host to temperatures as low as −61 °C, much lower than the supercooling point or lower lethal temperature of the weta. The freezing tolerance of the parasite is therefore much greater than that of its host. Female worms survived lower temperatures better than males and juveniles. Parasites might assist the freezing tolerance of their host if they acted as endogenous ice nucleators. However, there was no relationship between the size of the worm burden and the supercooling point of the host and no significant difference between the supercooling points of infected and uninfected hosts. The freezing and subsequent survival of isolated Wetanema was observed directly on a microscope cold stage. This parasite of a freezing- tolerant host is thus also freezing tolerant. There are few other reports of a parasite surviving freezing within a living host.