Optix reveals developmental homologies between wing patterns. (a) Optix expression is tightly associated with various Heliconius red wing patterns. Notice the interspecific difference in pattern boundaries relative to the Cu2 vein (dotted lines). The hybrid cross U70 is described in Figure 3. (b) Optix expression in the polymorphic Heliconius doris butterflies. Insets feature dorsal views of adult patterns. (c) Conserved association of Optix expression with red ‘proximal complex’ patterns (forewing bar and hindwing basal spots) across Heliconiini. Asterisks: color pattern-independent expression of Optix in dorsal patches of presumptive acute scales. Insets feature ventral views of adult patterns.