Visual cues and body volatile β-ocimene are used by the blue tiger butterfly Tirumala limniace to identify conspecifics during courtship

Abstract  Butterflies use visual and olfactory cues to identify conspecifics during courtship. Tirumala limniace , Idea leuconoe , and Danaus chrysippus are three species of butterflies with a sympatric distribution, and T. limniace butterflies are rarely seen to chase I. leuconoe or D. chrysippus during courtship in artificial cultivation gardens, indicating that they have a mechanism for recognizing conspecifics; however, there are no reports on what kind of signals they use to recognize conspecifics. In this study, we investigated the cues used by T. limniace to identify conspecifics and the relative roles of visual and olfactory cues. We found that in the absence of olfactory cues (visual cues only), male and female butterflies were able to identify the same species based on wing color and pattern. By collecting and identifying body volatiles emitted from T. limniace males and females, we found that the highest amounts were β -ocimene and β -pinene, which were sourced from the insects’ bodies (as opposed to sex pheromones). Furthermore, electroantennogram binding behavioral experiments showed that β -ocimene was involved in the process of species recognition and that the relative roles of olfactory cues were greater than those of visual cues at close range. Therefore, T. limniace males and females could utilize both visual and olfactory cues to identify conspecifics during courtship but preferred olfactory cues. The present study highlighted the important role of adult body odor rather than sex pheromones in butterfly species recognition. Significance statement Butterflies use visual (wing color and pattern) and olfactory (sex pheromones) cues to identify conspecifics during courtship. Butterflies also release volatiles emitted from their bodies during courtship. However, there is no clear evidence that body volatiles (as opposed to sex pheromones) emitted from butterflies are involved in species recognition. We studied the functions of body volatiles emitted from Tirumala limniace adults and the relative roles of visual and olfactory cues in species recognition during courtship. We found that male and female adults could identify conspecifics using only visual cues. Meanwhile, we also found that the highest amounts of β -ocimene, which came from the bodies of T. limniace males and females, were also involved in the process of species recognition. The olfactory cues that butterflies use to identify conspecifics are usually sex pheromones, while the present study highlighted the important role of adult body odor rather than sex pheromones in butterfly species recognition.