Average locomotor activity of P. occidentalis workers in DD conditions. Average levels of locomotor activity in individual P. occidentalis workers differ by task in DD conditions. Bars represent average values of locomotor activity in two-hour increments (w/SE, n = 5 foragers (A); n = 6 nest workers (B)). The gray stripe in the horizontal bar at base of the plot represents the subjective light phase and the solid stripe represents the dark phase in DD conditions. Forager activity levels (A) during the projected daytime were two times higher than activity levels in the projected nighttime. Nest workers (B) typically showed a brief peak of locomotor activity early in the projected morning and lower, variable levels of activity throughout the day and projected evening hours.