Desiccation resistance in two species of Drosophila.

Three populations of Drosophila pseudoobscura, each one represented by 12 isofemale lines, and one laboratory strain of D. melanogaster were tested for desiccation resistance at two time periods. Except in the case of one population of D. pseudoobscura, the ability to withstand drying was significantly greater in females than in the corresponding males. The males of the three populations of D. pseudoobscura differed significantly among themselves in their resistance to desiccation, as did the females. The females of D. melanogaster exhibited a consistently higher survival rate than those of D. pseudoobscura, but not the males. These results are discussed with reference to the third chromosome inversion polymorphism of D. pseudoobscura and the cosmopolitan distribution of D. melanogaster.