Responses of Various Strains of Drosophila pseudoobscura and Drosophila persimilis to Light and to Gravity

Abstract

Strains of Drosophila pseudo-obscura and D. persimilis vary in their reactions to light and to gravity. Some are positive, others neutral, and still others negative. D. persimilis is, on the average, more photopositive than D. pseudo-obscura; but there is a considerable overlap. Males tend to be more photopositive than females, but there are again some exceptions. The modal behavior with respect to gravity is geotactic neutrality in both species.