Experiments on Drosophila show that an evolutionarily conserved photoreceptor that senses light outside of the retina can regulate responses to direct visual cues.

1. The Evolution and Diversity of Pineal and Parapineal Photopigments -- 2. The Evolution and Function of Melanopsin in Craniates -- 3. The Evolution of Non-visual Photopigments in the Central Nervous ...