Usually, these animals inhabit caves or groundwater. They occur in western Eurasia, in regions that were not covered by the Pleistocene ice sheets. They are found throughout most of Europe with the notable exception of the Nordics and they are also largely missing from Iberia. The genus extends into Asia as far as the Arabian Peninsula and Iran. In their main range - the central Mediterranean region through Central and Eastern Europe to the Ukraine - they are among the most significant organisms inhabiting the groundwater. In the Dinaric Alps alone there are at least 45 species. There are also six species in the British Isles (the northernmost Niphargus): N. aquilex, N. fontanus, N. glenniei and N. kochianus of Great Britain, and N. irlandicus and N. wexfordensis of Ireland. Although the individual species often have very small ranges and only live at a narrow water temperature range, the genus includes both species of cold and relatively warm places, taken to the extreme in N. thermalis from thermal waters.