Fig. 3. Response threshold of bees in different arousal states. (A) Foragers. (B) Callows. Right panels: colony H23; left panels: colony S25. The response threshold to a light pulse differed significantly across arousal states, but not between callows and foragers. The central horizontal line in each box indicates the median, the box borders indicate the 75th and 25th percentile, and the error bars outline the range. Circles indicate outliers; values in a range spanning between 1.5 and 3 box lengths. Asterisks indicate extreme values: values in a range spanning more than three box lengths. Sample size (number of bees) is shown within or above each box. Different capital letters indicate arousal states that are statistically different (Kruskal–Wallis tests followed by multiple comparisons, P<0.0001 for both foragers and callows). FS, first sleep stage; SS, second sleep stage; TS, third sleep stage. Response threshold, at TS, was not determined for foragers in colony S23.