Figure 1.
A. Adult male L. arenicola. B. Close-up view of the eye arrangement on the carapace of L. arenicola. C. Schematic representation of the position of the anterior lateral eyes (ALE), anterior median eyes (AME), posterior median eyes (PME), and posterior lateral eyes (PLE). (B and C modified from Nørgaard et al. 2008).
Figure 2.
A. The body-to-burrow alignment angle α measured as the angle between the spiders' current walking direction and the direct line to the burrow. B. The visual fields of the anterior median eyes (AME) (light blue), anterior lateral eyes (ALE) (yellow), posterior median eyes (PME) (grey), and posterior lateral eyes (PLE) (magenta) on the right side of a L. arenicola visualised on a globe viewed from 15° above the horizontal plane (modified from Nørgaard et al. 2008). C. A visual field compass composed of the spider's visual fields (except the upwards-looking PME): this can be used to determine which eye(s) look back at the burrow for any given α.
Figure 3.
Illustrations of the 26 departures recorded from individual male spiders leaving their burrow for the first time in a completely unfamiliar area. The red dots mark the burrow position. The circles represent the 2 m radius circle around the burrow.
Figure 4.
Ontogeny of sinusoidal departure pattern.
The x-axis denotes the sequential departure of a spider from its burrow (1st: N = 26, 2nd: N = 16, and 3rd: N = 4). Departure paths are shown in the top pane. The circles represent the 2 m radius circle around the burrow. In the middle pane are the mean wavelengths of the sinusoidal paths. The amplitudes are shown in the bottom pane (y-axis is in cm). Error bars are standard deviation. While the amplitudes were not significantly different between departures, the wavelengths were (PERMANOVA, P = 0.0003).
Figure 5.
Effect of departure sequence on body-to-burrow alignment angle α.
Mean α and 95% confidence intervals for 1st (α = blue, N = 26), 2nd (α = green, N = 16), and 3rd (α = red, N = 4) departures on single nights pooled for left and right side depicted on a compass with the visual fields of the AM eyes (light blue), AL eyes (yellow) and PL eyes (magenta).
Figure 6.
Departures compared to returns.
Mean departure (dashed lines) and return (solid lines) path length (cm), duration (s), and speed (cm/s) as a function of departure or return number on single nights (see Table 1 for descriptive statistics).
Figure 7.
The direct distance to the burrow as a function of time in individual spiders reveals that the spiders move away from their burrow at a constant rate independent of the shape of the sinusoidal movement pattern they perform.
Table 1.
Descriptive statistics for excursion departures and returns.