The Unique Flight Strategies Adopted by Butterflies When Landing on Vertical Surfaces ^†

Landing on vertical surfaces poses a greater challenge for insects compared to horizontal ones, yet it remarkably expands their spatial range. Butterflies, adept at perching vertically, offer a compelling bio-inspired model. However, the mechanisms behind their landing behavior and the associated perceptual processes on vertical surfaces remain elusive. Similar to takeoff, understanding the distinctive strategies employed by butterflies during vertical landings is imperative. This encompasses the dynamics of self-stability, the role of visual perception in posture control, and the influence of asymmetric wing flapping on posture changes.

This research employs a high-speed camera system to comprehensively track the descent process of butterflies onto vertical surfaces. This study successfully captures a sequence of coordinated behaviors involved in wall landings. Kinematic analysis reveals the ability of butterflies to maintain body stability despite significant pitch rate variations. This suggests that, beyond flight mechanics, butterflies exhibit robust control over body posture influenced by other factors. Drawing on insect optic flow perception during landing, this study proposes three primary visual cues influencing butterfly landing behavior. Correlation analysis establishes connections between butterfly rotational maneuvers and visual cues. Finally, by delineating the asymmetrical differences in wing Euler angle changes, the corresponding relationships with posture angle variations are identified.