Applying a yellow light stimulus to larvae expressing Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} under the control of Scer\GAL4^Rapgap1-OK6 (and fed on all-trans retinal (ATR)) results in complete loss of locomotion and instantaneous relaxation of all muscles. Similar light-induced immobilisation is seen when Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} is driven by Scer\GAL4^VGAT, Scer\GAL4^futsch-C380, Scer\GAL4^Act5C.PI or Scer\GAL4^Cha.7.4.

When Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} is expressed under the control of Scer\GAL4^Rapgap1-OK6 or Scer\GAL4^futsch-C380, the entire body of the larvae contracts when light stimulation is switched off, before returning to normal peristaltic locomotion. This accordion-like contraction does not occur when Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} is expressed under the control of Scer\GAL4^Mhc.PW or Scer\GAL4^NP2225.

When larvae expressing Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} under the control of Scer\GAL4^Rapgap1-OK6 or Scer\GAL4^VGAT are exposed to the light stimulus for long periods of time, they initially stop their locomotion but resume movement after several tens of seconds, even in the presence of the light stimulus. The duration of inactivity is dependent on light intensity and the concentration of ATR. When larvae are exposed to blue light as well as yellow light, they are unable to resume movement for as long as the light is present.

Larvae expressing Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} in class 1 md and bd sensory neurons with Scer\GAL4^NP2225 show a reduced crawling speed in response to blue and yellow light stimulation. Wave duration (the time required for a wave of muscular contraction) is increased compared to controls.

When larvae expressing Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} in motor neurons under the control of Scer\GAL4^VGAT are exposed to a brief light stimulus (approximately 1s) during peristalsis the entire larval body relaxes, leading to the disappearance of the propagation of muscular contraction. However, the propagation reappears when the light is turned off, at around the segment that was about to contract when the light stimulus was given. A similar restart of propagation is seen when Zzzz\HR^{Scer\UAS.T:Avic\GFP-YFP} is expressed under the control of Scer\GAL4^Rapgap1-OK6 and Scer\GAL4^futsch-C380. Successful resuming of propagation can still be seen when light stimuli of 5 and 10 seconds are given, but less frequently. Applying the light stimulus to discrete segments at the forefront of the wave provokes a similar response. Muscular contraction does not occur when the light stimulus is applied to larvae in a quiescent state.