Distortion of the pleural arches in jumping. (A) Movement of the coxal end (see box in right image of B) of the pleural arch of the left hind leg when the left trochanteral depressor muscle was stimulated. Digital images under ultraviolet illumination at the start (cyan) and end (magenta) of the stimulation are superimposed. The colour changes were made in Photoshop, so that areas of overlap between the two images appear white. (B) Frames from a natural jump captured at 1000/second; the left frame was taken before the jump, the middle one after a 2-second long contraction of the trochanteral muscles, and the one on the right after the jump. The prolonged contraction results in a forward movement of the coxae (arrow and lines), which is reversed when the hind legs depress and extend in a jump.