The significance of moment-of-inertia variation in flight manoeuvres of butterflies.

The objective of this study is to understand the role that changes in body moment of inertia might play during flight manoeuvres of insects. High-speed, high-resolution videogrammetry is used to quantify the trajectory and body conformation of Painted Lady butterflies during flight manoeuvres; the 3D kinematics of the centre of masses of the various body parts of the insect is determined experimentally. Measurements of the mass properties of the insect are used to parameterize a simple flight dynamics model of the butterfly. Even though the mass of the flapping wings is small compared to the total mass of the insect, these experiments and subsequent analysis indicate that changes in moment of inertia during flight are large enough to influence the manoeuvres of these insects.