Comparative analysis on visual and olfactory signals of Papilio xuthus (Lepidoptera: Papilionidae) during foraging and courtship

This study examined the roles of visual and olfactory responses during foraging and courtship in butterfly Papilio xuthus. P. xuthus showed obvious orientation to color in the range of 350–500 nm. Visits of P. xuthus females and males to blue, purple, and red artificial cloth flowers were ♀ 54.90% and ♂ 39.22%, ♀ 19.61% and ♂ 35.29%, and ♀ 9.80% and ♂ 19.61%, respectively. Application of 10% honey on these artificial flowers resulted in an increase of 3.41 and 3.26 fold in flower visits by the butterfly compared to controls. When 10% honey water was sprayed on flower branches without colorful flowers, branch visiting was very low, only seven times for females and two times for males, indicating that colors might be more critical than odor for foraging even though visual and olfactory perceptions both play important roles during foraging. During courtship, four types of chasing were observed in a natural population of P. Xuthus; the four types are males chasing females (49%), males chasing males (25%), females chasing males (13%), and females chasing females (10%). However, when odorless artificial models of butterflies were used, no significant differences were observed among these types of chasing, indicating that olfactory perception was crucial for the butterfly during courtship. Profiling volatile organic chemicals (VOCs) and individual bioassays revealed that VOCs contents of butterflies were not related to recognizing sex partners; by contrast, some level of α-farnesene, increased the frequency of male chasing female. This could be due to that α-farnesene is easy to be detected by butterflies because of its volatility and higher content in female.