Colour Selection and Olfactory Responses of Papilio demoleus during Foraging and Courtship

SIMPLE SUMMARY: In this work, we analysed the visual and olfactory sensory responses of the butterfly Papilio demoleus during foraging and courtship. We found that P. demoleus has a preference for red and orange. There is a significant difference between the visual and olfactory behaviour of both males and females; males rely more on visual cues, and females respond more to olfactory signals during foraging and courtship. Colour is the dominant factor during foraging and courtship; members of P. demoleus find the target by colour. Butterfly movement is an important role during the courtship of P.demoleus, and odour can increase accurate recognition of males and females. Opsin genes of P. demoleus were analysed, and we found that P. demoleus have genes that recognise the long wavelength, blue and ultraviolet regions of the spectrum. These pieces of evidence are beneficial to understand the coevolve of the butterfly and plant. ABSTRACT: Colours and odours are the most important cues for butterflies to localise food and mating partners. We studied the visual and olfactory responses of the widely distributed butterfly Papilio demoleus Linnaeus during foraging and courtship. P. demoleus visited odourless flowers with six colours except green and black, with red as the favourite colour (650–780 nm). Males and females differed in behaviour while visiting flowers. Males were more active than females during foraging. The application of honey water resulted in a significant increase in flower visits by both females and males, and they scarcely visited the apetalous branches with odours. Under natural conditions, four patterns were observed: males chasing males (42.28%), males chasing females (30.56%), females chasing females (13.73%), and females chasing males (13.43%). Males chasing males was the most frequent, probably because males drive away competing con-specific males. When butterflies visited odourless mimics, males chasing females (70.73%) and males chasing males (29.27%) also occurred, indicating that males could accurately distinguish mates using colours only without any chemical cues, and females need chemical cues. The behavioural responses of P. demoleus to floral visits and courtship suggest that colour is the dominant factor during foraging and courtship. We verified the presence of P. demoleus rhodopsin genes, including Rh2, Rh3, Rh4, and Rh5, for long wavelength, blue, and ultraviolet (UV) spectrum recognition, which is consistent with the colour recognition of flowers and wings during visiting flowers and courtship.