The free-running locomotor activity rhythm period is unaffected when cryScer\UAS.cIa is expressed under the control of Scer\GAL4per.PK, Scer\GAL4ninaE.PHS or Scer\GAL4Act5C.PHb. Expression of cryScer\UAS.cIa under the control of Scer\GAL4Act5C.PHb alters the light response of locomotor activity.