Expression is first seen in 4-5hr old first instar larvae at ZT0, though DN2 neurons stain most readily at ZT12. During the first 40% (prepupal to pupal stage) of pupal development, expression is seen only in the 4-5 LNs, and generally not in the DNs except for a single weakly labeled cell near the region of the DN2 in 1 of 16 examined hemispheres at ZT0. At approximately 50% pupal development (pharate adult stage), expression begins in DN1s, DN2s and the l-LNvs. At approximately 60% of pupal development, expression begins in the LNd and the DN3 neurons. Apart from DN2s and DN3s, all pupal cells expressing per^{BG.T:EcollacZ} show cycling of the LacZ staining with a phase similar to the larval neurons. Peak expression in the larval LNs and DN1s is at ZT23, and a trough at ZT6-12. Peak expression in the larval DN2s is at approximately ZT12 and a trough at ZT0.