Initial mate recognition in the British cabbage butterfly, Pieris rapae rapae

Visual features of the wing color, with special reference to the UV (ultrav iolet) color, or the British subspecies of the cabbage butterfly, Pieris ra pae rapae and its mating behavior were investigated. Both sexes of the Brit ish subspecies were found to lack UV color and differed only slightly in co lor in the visible color range, with female wings more yellowish. It follow s that they show only slight sexual dimorphism in wing color. It was shown that the initial mate recognition was mediated visually, based on the wing color. Males discriminated between the sexes visually, but only marginally and were occasionally observed to approach other males mistakenly. The rest ing males approached by female-searching males displayed a flutter response , deterring the approaching males from attempting to copulate with them; i. e. it functioned as "mechanical isolation mechanism" against maladaptive co pulatory attempts between males. The results are discussed in terms of the comparative ethology of the mating behavior with that of the Japanese subsp ecies. It is suggested that the British subspecies is ancestral to the Japa nese subspecies.