Sex in Pieris rapæ L. and the Pteridin Content of their Wings

Abstract

WHEN Pieris rapæ L. was photographed under the illumination of ultra-violet light passing through the filter UV-D1 obtained from the Matsuda Lamp Co., the wings of female butterflies, in accordance with the description of Frank Lutz¹, showed a white image, for they reflected the light, whereas those of male butterflies gave a black shadow because they absorbed the ultra-violet light strongly, as seen in the accompanying photograph (Fig. 1); this is in striking contrast to photographs taken in daylight (Fig. 2). Experiments carried out to elucidate the mechanism of this phenomenon showed that it is due to the difference of pterin content between the male and the female wings.