<p>A. Cartoon of the froghopper <i>Philaenus</i> as viewed from the side. B. Ventral view of the posterior part of the thorax of <i>Philaenus</i>. The right hind leg is shown partly depressed and the left hind leg levated with its femoro-tibial joint between the ventral surface of the body and the femur of the left middle leg, held as in preparation for a jump. C. Ventral view of the right half of the metathorax of <i>Philaenus</i> (area indicated by box in B) dissected to reveal the massive pleural arch (tinted grey-blue) which with its counterpart on the other side of the body forms the energy store for jumping. D. Photograph of a ventral view of the metathorax of <i>Delphacodes</i> in which images illuminated with white and UV light have been superimposed to show the blue fluorescence of the pleural arches. The horizontal lines indicate the region from which the transverse sections shown in subsequent figures were taken.</p
