Fig. 8. Kinematics of the head–scape (H–S) joint in two behavioral states. The S–P joint is immobilized in this condition (see inset at bottom). (A) Trajectories showed two-dimensional expansion in both states. During walking, both antennae concentrated at lower positions. (B) Power-spectra of horizontal (H) and vertical (V) components in the two states. Peaks at <2 Hz decreased in walking for both components. These spectra were obtained from the time-series whose trajectories are shown in A. (C) Mean angular ranges (bars) and central positions (symbols) of both antennae during pausing and walking (N=4). Vertical central positions for both antennae were significantly lowered as observed in the S–P joint free condition (see Fig. 7). Horizontal working ranges were slightly but significantly narrowed during walking. Inset indicates two rotation axes of the free H–S joint. Sampling periods and abbreviations, see Fig. 7.