The circadian eclosion rhythm in Sarcophaga argyrostoma: delineation of the responsive period for entrainment

ABSTRACT. The circadian rhythm of pupal eclosion in Sarcophaga argyrostoma shows a declining responsiveness to the phase‐shifting effects of single light pulses as development proceeds, the intrapuparial stages becoming largely ‘insensitive’. Maximum responses occur in the intra‐uterine embryos and first‐instar larvae. Pharate adults, however, are responsive to single high temperature pulses. Pupae, pharate adults, and females carrying ovarian eggs, also respond to single stepwise transfers from light to dark, or vice versa, but the peaks of eclosion show a phase angle to the light which differs from that produced by transfers of embryos or larvae. The results are consistent with the view that separate ‘larval’ and ‘adult’ clocks occur at different stages of development.