Fig. 3. Turning in the intact stick insect on the slippery surface. (Ai-iii) Three typical walking sequences with the anterior extreme position (AEP) and posterior extreme position (PEP) connected by arrows for one straight walking sequence (Ai, black), and two curve walking sequences (Aii and Aiii) of differing steepness. Red marks inside legs, yellow marks outside legs. (B) Schematic drawing of a stick insect with the mean AEP and PEP values (and s.d.) for the straight walking and turning animal. Red marks the values for the averaged steps for the inside leg, dark yellow for the outside legs and black for the straight stepping legs (from Fig. 2). The light gray lines mark the respective x₀-value for the middle (ML) and hind (HL) legs. (C) Mean vectors of stance phase movement of the inside (red), outside (dark yellow) and straight stepping (black) left legs, drawn to the mean step length as calculated between AEP and PEP. (D,E) Step-to-step variability in angle and length of all stance phase movement vectors for the inside (D, red) and outside (E, yellow) front, middle and hind legs (iFL, inside front legs; iML, inside middle legs; oFL, outside front legs; oML, outside middle legs). All vectors of the right side legs were again mirror imaged to show only left side stepping; coloring is the same as in A.