Currently, biological control through the use of plants is of paramount importance to limit the nuisance of several insect pests. In this study we evaluated the different effects of Citrullus colosynthis aqueous extract on Drosophila melanogaster; we started with determining the toxicity of this fruit against the second instar of D. melanogaster larvae by using 3 different concentrations (50g/l, 100g/l, 150g/l). 50% mortality among the tested individuals was reported after 48 hours after treatment and reaches 93% on the 12^th day. Thereafter we studied the delayed effects of sublethal concentrations on the sexual behavior in adults emerging from sublethal concentration treatment. We noticed a disturbance in some sequences of the courtship such as allied vibration, licking, mating, and a decrease in successful mating rate.