This paper deals with the structure and function of the intracerebral ocelli in the caudal area of the brain of the Japanese firefly. A pair of epilaterally placed specialized pigmented organs was found at the caudal ends of the brains of the fireflies Luciola cruciata and L. lateralis. On the basis of light and transmission electron micrographs of both male and female individuals these organs seemed photoreceptive in nature. Intracellular and extracellular recordings were obtained from the intracerebral ocelli of the fireflies with microelectrodes. The physiological evidence revealed that the cells found in the brain were, indeed, photoreceptors.