Biomechanics of Flight in Neotropical Butterflies: Morphometrics and Kinematics

Wing and body kinematics of free cruising flight are described for 37 species of Panamanian butterflies ranging over two orders of magnitude in body mass. Butterflies exhibit considerable diversity in body and wing shape, but morphological design is, in general, isometric. Wing loading and mean body diameter show positive allometry. The cruising flight of butterflies is characterized by low wingbeat frequencies (here averaging 11 Hz), stroke amplitudes averaging 103°, and forward speeds in excess of lms". Body angles during flight are close to horizontal, and stroke plane angles are correspondingly high. Advance ratios are typically greater than 0.9, indicating that the forward and flapping velocity vectors are of comparable magnitude. Flight speed scales with morphological parameters in general accordance with predictions based on isometric design. Interspecifically, no consistent correlation exists between wing kinematics and absolute flight speed. However, maximum positional angle and stroke amplitude tend to increase while body angle decreases with increased relative flight speed.