[Objectives]  To determine the effect of copper ions on the selection of oviposition sites by Drosophila, and the toxicity of copper ions to both parents and progeny. [Methods]  The effect of copper ions on the choice of oviposition sites by adult female Drosophila were evaluated using a two-choice apparatus. To determine the role of vision in female oviposition preferences some choice experiments were carried out in darkness. The sensory systems mediating this behavior were investigated by surgically removing the taste receptors from the forelegs and the olfactory receptor from the antennae. Drosophila were also cultured on media containing various concentrations of CuSO₄ and the developmental duration and survival of offspring from each treatment were compared to evaluate the biological significance of avoidance of copper ions during oviposition. Fitness was assessed on the basis of survival rate and locomotion. Levels of ROS in the gut were measured with DHE staining. [Results]  Adult female Drosophila avoided laying eggs on media containing 3, 5 and 6 mmol·L^-1 CuSO₄. Oviposition indices on these media were ﹣0.33, ﹣0.54 and ﹣0.78, respectively, indicating that oviposition declined in a concentration-dependent manner. Darkness and olfaction did not affect the avoidance of copper ions by female Drosophila. Partial taste-impaired and taste-impaired flies avoided laying eggs on the media containing 3, 5 and 6 mmol·L^-1 CuSO₄; oviposition indices on these media were ﹣0.27, ﹣0.42 and ﹣0.55, respectively. There was no significant difference in the oviposition indices of taste-impaired flies and the control, but there was a tendency for taste-impaired flies to be less averse to copper ions. Raising larvae on media containing 2.4 mmol·L^-1 CuSO₄ prolonged puparium formation and adult emergence by 2.5 d and 1.8 d, respectively, relative to the control, and larval and adult survival rates of offspring raised on this media decreased by 13.9% and 13.7%, respectively. Flies had lower survival and locomotion rates on media containing 36 mmol·L^-1 CuSO₄. [Conclusion]  Copper ions activate the Drosophila immune system by elevating ROS levels in the gut. Adult female Drosophila avoid ovipositing on media containing copper ions, and activate their immune system when exposed to these, in order to resist copper stress.