Development of fluorescence during maturation of successive larval stages of Philaenus. (A)and (B) In two larvae with body lengths of 4.1 mm and 4.8 mm, there was no fluorescence at the thoraco-coxal joints as there was in adults (diagonal yellow arrows). Some fluorescence is apparent in the soft membrane between the proximal joints of the hind legs and in the mouthparts (horizontal black arrow in A). (C) A larger larva (5.2 mm body length) shows strong fluorescence at the thoraco-coxal joint of the left but little at the right hind leg. (D) In the larval stage (6.7 mm long) preceding the final moult to adulthood, fluorescence is present at both thoraco-coxal joints. In (A), the two hind legs are photographed in one image, in (B)-(D), they are represented in two images. The dotted lines indicate the midline.