Hydroscapha redfordi Maier, Ivie, Johnson, and Maddison, new species, is described from a hot spring in northern Idaho. This new record extends the range of the genus in North America, and marks a new northern-most limit for the family worldwide. Hydroscapha redfordi is distinguished from Hydroscapha natans LeConte by both morphological characters and characters of two genes: the mitochondrial gene cytochrome oxidase I and the nuclear gene for 28S ribosomal RNA. Previous species concepts of H. natans are reviewed, and several populations inhabiting hot springs in Idaho and Nevada are now hypothesized to be independent species, leading to a prediction of many undescribed species remaining to be discovered.