Colour constancy of the swallowtail butterfly Papilio xuthus

We have recently shown that the Japanese yellow swallowtail butterfly Papil io xuthus uses colour vision when searching for food, In the field, these b utterflies feed on nectar provided by flowers of various colours not only i n direct sunlight but also in shaded places and on cloudy days, suggesting that they have colour constancy, Here, we tested this hypothesis. We traine d newly emerged Papilio xuthus to feed on sucrose solution on a paper patch of a certain colour under white illumination, The butterflies were then te sted under both white and coloured illumination, Under white illumination, yellow- and red-trained butterflies selected the correctly coloured patch f rom a four-colour pattern and from a colour Mondrian collage. Under four di fferent colours of illumination, we obtained results that were fundamentall y similar to those under white illumination. Moreover, we performed critica l tests using sets of two similar colours, which were also correctly discri minated by trained butterflies under coloured illumination, Taken together, we conclude that the butterfly Papilio xuthus exhibits some degree of colo ur constancy when searching for food.