Expression of PoPer mRNA in spring nestworkers and foragers (LD conditions). Relative expression of period mRNA in individual worker brains from experimental colonies of P. occidentalis collected in the spring (w/SE). Colonies were entrained in controlled environmental chambers in a 12:12 hr LD regime. Foragers were collected at six time points (dark bars, n = 4 colonies) and nest workers were collected at 4 time points (light bars, n = 4 colonies). Bars represent the averages of colony means with three nest workers and three foragers sampled per colony (SE calculated from colonies). The open stripe in the horizontal bar at base of the plot represents the light phase and the solid stripe represents the dark phase. All individuals were collected for analysis in dark conditions.