The effect of light on the sexual behavior of Drosophila affinis.

Drosophila affinis is a species whose mating is facilitated by light. Although sexually mature D. affinis males court D. affinis males and females vigorously in the light, they do not perform any of the courtship behaviors in the dark. This lack of courtship is not caused by the males and females being unattractive in the dark, since D. affinis males and females elicit high levels of courtship from Drosophila melanogaster males in light and in darkness. Fertility tests confirmed previous observations that mating occasionally occurs in the dark, suggesting that some D. affinis males are capable of courting in the dark.