Genes relevant to manifestion of and variation in locomotor behavior might be differentially expressed in lines selected for divergent levels of locomotion. Experiment Overall Design: Drosophila adults were assessed for locomotor reactivity levels in a behavioral assay that quantified the locomotor response to a mechanical stimulus. A subset of the sampled population was selected as parents for the next generation, with High, Low, and Control selection groups maintained. This artificial selection was continued for 25 generations, with a variety of other behavioral and life history traits assessed for correlation with response to selection for locomotion. At generation 25, male and female flies were collected for RNA extraction and subsequent gene expression analysis.