ABSTRACT.The time course of dark adaptation inApis meliferaL. was investigated by analyses of phototactic behaviour and electroretinogram (ERG). The behavioural results give a function for dark adaptation showing that in the dark after strong light adaptation the sensitivity increases exponentially with a time constant of 3 min. The sensitivity changesc.2.4 log units during the time span of 5–720 s. The electrophysiological results indicate a smaller change in sensitivity at the level of the photoreceptors. Within a time span between 20 and 720 s the sensitivity increases during dark adaptation by a factor of 4.3 on a linear scal