Multiple extraocular photoreceptive areas on genitalia of butterfly Papilio xuthus

Abstract

Extraocular photoreception has been reported in several orders of insects, and direct photoreception by the central nervous system (CNS) has been shown to be related to the circadian clock in many cases¹. For example, CNS photoreceptors have been found in the brain and the last abdominal ganglion of the cockroach, Periplaneta americana, and in the brain of the silkworm, Hyalophora cecropia². In other cases dermal light sensitivity has been deduced from behavioural responses. For instance, the larvae of Tenebrio molitor avoid light even after decapitation³. The antennae of Aphis fabae seem to be the site of light sensitivity responsible for the animal's photokinetic activity⁴. Dermal light sensitivity is demonstrable in all the tergites of the larvae of Acilius japonicus and Dytiscus marginalis, particularly well developed in the region of terminal abdominal spiracles⁵. We report here, however, the electrophysiological response and morphological characteristics of presumptive photoreceptive sites on the genitalia of the Chinese yellow swallowtail butterfly, Papilio xuthus L.