Sleep Tight, Fly Shortly after eclosion, young flies sleep a lot and are resistant to being woken. Several days later, the same flies sleep less and are more easily woken. Kayser et al. (p. 269 ) show that the different sleep pattern characteristic of youthful flies is critical to correct development of their brains. When sleep is disrupted in young flies, dopaminergic signaling is also disturbed and a glomerulus in the courtship behavior circuit does not develop properly, leading to inadequate courtship behavior and failure to reproduce.