Drosophila male courtship behavior is modulated by ecdysteroids.

Temperature-dependent induction of ecdysteroid deficiency in the ecdysoneless mutant ecd(1) adult Drosophila melanogaster results in altered courtship behavior in males. Ecdysteroid deficiency brings about significantly elevated male-male courtship behavior including song production resembling that directed toward females. Supplementation with dietary 20-hydroxyecdysone reduces male-male attraction, but does not change motor activity, courtship patterns or attraction to females. These observations support the hypothesis that reduced levels of ecdysteroids increase the probability that male fruit flies will display courtship behaviors to male stimuli.