Fig. 1. Body posture of honeybee workers in various arousal states. Each photograph is a single frame taken from continuous 24 h video recordings. (A) Immobile–active state (IA) – the bee stays in the same place, the thorax, abdomen and head are clearly raised above the substrate. This bee is moving her wings. (B) First sleep stage (FS) – the abdomen and thorax are clearly raised above the substrate, and the antennae are extended at an angle of 90–180° between the pedicle and the scape. (C) Second sleep stage (SS) – the body is typically more adjacent to the substrate, and the antennae are extended at an angle of 90° between the pedicle and the scape. (D) Third sleep stage (TS) – the muscle tonus is reduced, and the body is adjacent to the substrate. The angle between the pedicle and scape <90°, with the antennae tips typically touching the substrate. For more details, see Table 1.