In several insect species, the foraging behaviour has been demonstrated to be controlled by the foraging gene ( for ) which encodes for a cGMP-dependent protein kinase (PKG). In wild Drosophila populations, rover and sitter individuals coexist and are characterized by high and low PKG activity levels respectively. Because of their increased foraging behaviour, we postulated that rover flies are more exposed to environmental stresses than sitter flies. Thus, we tested whether rover and sitter flies differ in their fitness by using insecticides as chemical stressors. We showed that their responses are different depending on the insecticide used and are linked to variations of cytochrome P450s activities. Furthermore, the expression of the insecticide metabolizing cytochrome P450 Cyp6a2 was shown to be under the control of the for gene. We evidence here a new physiological function for the for gene in Drosophila and we demonstrate its involvement in the adaptation to chemicals in the environment.