Abstract
Light irradiation stimulates blue coloration in the band region of the adult wing of a butterfly, Graphium sarpedon whereas the region remains yellow in darkness. This blue color is due to the presence of a blue bilin pigment (sarpedobilin). In the present study, we show that the amount of blue bilin in the wing band region increases with increasing intensity or duration of light exposure. Further, blue bilin accumulation occurs when local irradiation of light falls on the wing, but not on the adult body. This remained true even when only the wing separated from an adult body or only the limited region of the wing band pattern was exposed to light. Blue light is more effective than green or red light. Microscopic observations show that the blue coloration is derived from part of the wing membrane, but not from wing scales. These results strongly suggest that light acts directly on the wing tissue without the intervention of a neuroendocrine system, and increases the amount of blue bilin in the wing membrane.
