@article{oai:ir.soken.ac.jp:00003493,
 author = {蟻川, 謙太郎 and ARIKAWA, Kentaro},
 issue = {3},
 journal = {BioScience, BioScience},
 month = {},
 note = {application/pdf, Butterflies sense light with their genitalia. Four photoreceptor cells in the genitalia mediate this photosensitivity. Such photoreceptors, which exist in body parts other than eyes, are collectively called extraocular photoreceptors. Extraocular photoreceptors have been found in various groups of animals, both vertebrates and invertebrates (Yoshida 1979). One of the most extensively studied cases is the photoreceptor cells in the pineal gland of the vertebrate brain: The pineal photoreceptors receive light to entrain animals' daily activity.

In arthropods, extraocular photoreceptors are roughly divided into two types, according to their general location. The first type is found in the central nervous system. A classic example is the crayfish caudal photoreceptor, a photoreceptive interneuron in the abdominal nervous system, which mediates an escape response upon light stimulation of the abdomen (Wilkens 1988). The second type is found outside the central nervous system as sensory neurons, with the photoreceptive site located on the periphery of the animals. The existence of the peripheral type of photoreceptor had long been indicated in certain scorpions (Zwicky 1968), but the first conclusively documented case was that of the butterfly genital photoreceptors (Arikawa et al. 1980).

In this article, I give an overview of the studies that my colleagues and I have conducted on the genital photoreceptor system of the butterfly. After describing how this unique photoreceptive system was discovered, I then describe the response characteristics and the anatomy of the photoreceptor cells and conclude with a discussion of how butterflies use the genital photoreceptors.},
 pages = {219--225},
 title = {Hindsight of Butterflies  The Papilio butterfly has light sensitivity in the genitalia, which appears to be crucial for reproductive behavior},
 volume = {51},
 year = {2001}
}