International Ethological Conference, 25th (1997), Vienna
Laboratory of Ethology, Department of Veterinary Medicine, Tokyo University of Agriculture and Technology
ABSTRACT. The intensity of light of shorter wavelengths including near ultraviolet light (nUV) is susceptible to changes in local or weather conditions such as shadow or clouds. Measurements showed that the relative intensity of nUV light to that of visible light is markedly higher in the shadow than in the sunlight. It follows that nUV colour patterns on the wing of females of the cabbage white butterfly (Pieris rapae crucivora, Lepidoptera: Pieridae), which are essential components of the mate recognition mechanism of conspecific males, may change depending on these environmental conditions. The "Bee Camera" devised by NHK which displays nUV light as red, green or blue colour showed that female colours appeared differently according to different light conditions. On sunny days females appeared in markedly stronger nUV colour when they were in the shadow than they did when exposed to sunlight. When cloudy they appeared in much less intense nUV colour looked more similar to males. We found that males preferred females located in the shadow to those in sunlight. This suggests that the typical female colour to which male vision is tuned is that displayed in the shadow. Males changed their search behaviour for females in an adaptive manner in response to the female wing colour change.