Expression of PoPer mRNA in fall foragers in LD and DD conditions. Relative expression of period mRNA in individual forager brains from experimental colonies of P. occidentalis collected in the early fall (w/SE). Colonies were entrained in controlled environmental chambers in either a 12:12 hr LD regime (light bars, n = 5 colonies) or a 24 hr DD regime (dark bars, n = 3 colonies). Bars represent the averages of colony means (four individuals sampled per colony at six time points for both light regimes; SE calculated from colonies). The diagonal stripes in the horizontal bar at base of the plot represent the actual (LD) or subjective light phase (DD) and the solid stripe represents the dark phase. All individuals were collected for analysis in dark conditions.