Circadian rhythms of the German cockroach (Dictyoptera: Blattellidae): Locomotion in response to different photoperiods and wavelengths of light

Male German cockroaches, Blattella germanica (L.), exposed to 12 h light-12 h dark, constant darkness and constant light in ultraviolet (u.v., 365 nm peak), blue green (495 nm peak) or white (about 400–1100 nm) light exhibited different rhythms and magnitudes of locomotion. All wavelengths induced a bimodal pattern of nocturnal activity in 12 h light-12 h dark, which was maintained as a free-running rhythm with a shorter period in constant darkness; activity was suppressed in constant light. Ultraviolet caused the greatest change in locomotion during transitions between photoperiods, but blue-green established a free-running rhythm that was maintained for longer. Since different sensory cells and perhaps pathways are involved in processing ultraviolet and blue-green light, ultraviolet could mediate direct responses to light stimuli and blue-green may regulate more complex behaviour.