Optix is transiently expressed in a small population of optic lobe neurons. (a) Expression of Optix in Heliconius optic lobes at the pre-ommochrome stage. Similar results were obtained for H. doris and H. sapho. (b) Lack of Optix expression in optic lobes and retina at the adult stage. Immunodetection of the photoreceptors UVRh1/2 is shown here in ommatidia as a positive control. This negative result was replicated in H. melpomene, H. cydno, and H. doris. La, lamina; Lo, lobula ; Me, medulla; Re, retina. OL, optic lobe. Scale bars: 100 μm.