Circadian control of spontaneous flight activity in the blowfly, Lucilia cuprina

Under laboratory light: dark cycles, the flight activity of adult Lucilia cuprina (Wied.) was low during darkness and uniformity high during light. This pattern persisted as a rhythm both in constant darkness and in constant light of intensity up to 1lx, with a period of approximately 22 h in each. Light pulses of 15 min at l00lx applied to the free‐running rhythm in constant darkness generated phase shifts of up to 60°, 12‐h light pulses of the same intensity generated maximal (180°) phase shifts. The phase response curves had shapes similar to those of a number of other insect rhythms. When exposed to light periods (70 lx) of greater than 12 h followed by constant darkness, the rhythm reinitiated at the light‐dark transition from a constant phase equivalent to that at the time of the light‐dark transition in the LD 12:12 cycle.