Fig. 3. Locomotor development in wild-type Drosophila embryos. Movements recorded from three embryos imaged from 16 hours AEL until hatching (around 21 hours AEL) using muscle imaging. From 17 hours AEL, muscle activity is episodic: sustained (30 seconds-2 minutes) bursts of muscle contraction are separated by longer periods of relative quiescence. The first complete wave of forward peristalsis occurs at 18.25 hours AEL and the traces are aligned at this point. Black bars indicate hatching.