Fig. 2.

Determination of COM. (A) Photograph of the frozen locust with a red thread attached to wax on the dorsal surface against an imperial and metric ruler. Only the one-sixteenth of an inch marks are visible in this picture. The reference point on the head is marked by a red dot; the measured COMs for different body angles (see B) are marked by yellow dots (an outlier is marked by the magenta dot), and their average is marked by a green dot. (B) A plot of the distance (in mm) of the attached string to the reference point vs the body angle (ϕ), and an illustration of the calculation of the COM (inset). The thread is attached vertically at d, and the reference point is at a (red dot). The distance from d to a varied linearly with the angle (ϕ) of the body from the vertical (R²=0.983, P7.7e–5). The position of the horizontal COM, b, along the line a–d was read from the regression line for an angle ϕ of 90 deg (dotted line in plot). The vertical COM (c, cyan dot) was determined by finding the intersection of a line extending the thread attachment (e–d) with a line (b–c) through the horizontal COM (b) perpendicular to a–b. (C) Image of the virtual locust with the position of the COM marked as a green dot.