Utilization of petal angle and floral shadows in the foraging behavior of the swallowtail butterfly Papilio xuthus (Lepidoptera: Papilionidae)

Butterflies locate flowers while flying and find nectar after landing, which is time and energy‐intensive. Butterflies rely on visual cues such as flower color, which they can learn through experience to optimize foraging efficiency. While many studies have focused on color in butterfly foraging behavior, flowers also have other potential visual signals that may facilitate localization, such as the petal angle and shadows cast inside the flower by petal inclination. However, these traits have not been widely considered as floral signals utilized by insects. This study investigated whether Papilio xuthus uses petal angle and floral shadows to improve foraging efficiency. First, we conducted choice tests using non‐angled flowers and angled small flowers. Adult P. xuthus visited angled small flowers more frequently than non‐angled flowers, indicating that when flowers of different shapes are in the same place, naïve P. xuthus preferentially visits flowers with angled petals. Second, we compared the success rates of feeding behavior between angled and non‐angled flowers. Female adults exhibited higher success rates of foraging behavior on angled flowers than on non‐angled flowers, implying that petal inclination facilitated nectar acquisition. Finally, we conducted choice tests between brightly colored flowers and flowers that mimicked the presence of shadows. Both males and females tend to visit shadow‐mimicking flowers more frequently than uniformly bright flowers, suggesting that centrally located shadow‐like patterns can influence flower choice. This study underscores the criticality of previously overlooked floral traits (petal angles and shadows) in butterfly foraging and provides new insights into butterfly behavioral ecology.