Fig. 5. Measured and predicted forces for a tethered larva. (A) The legend for the direction of force data (B—H). Violet traces represent lateral forces that are directed to the right of the body when negative and to the left when positive. Green traces show force along the antero-posterior axis of the trunk that is directed toward the anterior when positive and toward the posterior when negative. (B—H). As in Fig. 4, the vertical gray bands show when the trunk angle () is directed toward the left side of the body, and white bands occur when the trunk angle is directed to the right. Note that (B) the form force and (C) the acceleration reaction are on the same scale as the measured force, but both (D) the tail inertia force and (E) skin friction are plotted on smaller scales. (F) The tail force predicted for quasi-steady (F=F_f+F_s, heavy line) and unsteady models (F=F_f+F_s+F_a, thin line) illustrate the differences between these models. (G) Force generated by the larva against the tether, in the lateral direction for unfiltered (points) and filtered (line) data (see text for details). (H) Variation in trunk angle with time (the line is filtered data and the points are unfiltered).