Sample parameters measured by MaggotTracker. More parameters measured by MaggotTracker can be found in Table 1. A) MaggotTracker measures animal movements. Two 10-second videos of the same animal showed the differences between striding and non-striding movements. Several parameters are measured during the striding phase only. For example, stride duration is the time for one peristalsis cycle; extension and contraction rates measure the rate of length changes. Other parameters such as length and speed are measured at all time. Some parameters such as speed are measured for each point along the midline from head to tail. B) MaggotTracker traces animal tracks. Grey ring shows the position of the plastic ring used to prevent animals from crawling off the agar. Direction change points are marked red. C) MaggotTracker measures animal shape. Head angle and body angle are calculated to determine whether there is a head bend or a body bend.