EFFECTS OF CONSTANT LIGHT ON THE RHYTHM OF ADULT LOCOMOTOR-ACTIVITY IN THE BLOWFLY, CALLIPHORA-VICINA

Females of the blowfly, Calliphora vicina, showed an increase in the f ree-running period (tau) of their locomotor activity rhythm when trans ferred from continuous darkness (DD) to continuous 'dim' light (LL) at an irradiance below about 0.03 Wm(-2). Transfer to LL of this intensi ty also caused a reduction in the duration of the active phase (alpha) of the cycle. Transfer to 'bright' light (>0.03 Wm(-2)), however, lea d to arrhythmicity. Data suggest that constant light of this intensity does not 'stop' the circadian pacemaker but imposes behavioural arrhy thmicity at a more superficial level.