Progressive development of the eye from L1 larvae (A) to 48h APF (F) was visualized through differential interference contrast (DIC) optics (A-F). L1 (A) and L2 (B) larvae possess fairly simple larval eyes (Ley) that are visible at least through 48 h APF; it is unclear if these persist in adults. By stage L3, the adult eye is also visible (C), and it is noticeably larger in L4 animals (D). By the pupal stage (24 h APF in E, 48 h APF in F), additional rows of differentiated photoreceptor cells are visible in the adult eye, which has become a complex primary visual center. Scale bar = 25 microns; Ley: larval eye; Aey: adult eye; MP: mouth parts. Dorsal is oriented upward in all panels.