Although remaining in water balance is necessary for all organisms, the strategies for reducing water loss vary between species, depending on environmental conditions as well as on physiological and morphological considerations. Six species of Drosophila from 3 species groups and a variety of habitat types have been examined for some water balance properties. Two sibling species from Hawaii have been studied in more detail. All 6 species studied lose water rapidly at all test a v 's (relative humidity/100) below saturation, but the rates at which water loss increases when the a v is lowered vary between species. The 2 Hawaiian species from different habitats are strikingly different in water balance properties and survival characteristics at 0.70 a v . One population of D. mimica which was collected in a very dry area was much more tolerant of desiccation than were the other populations of the same species.