Insect photoreceptor: an internal ocellus is present in sphinx moths

Adult sphinx moths lack external ocelli. In Manduca sexta and other anocellate moths structures homologous to ocelli have been observed. Histological examination of such a structure in Manduca sexta has shown structural similarities to ocelli of other insects. Electrophysiological studies revealed a response to light stimuli stimilar to the electroretinogram of external ocelli. The evidence strongly suggests that the structures are internal ocelli.