Three-dimensional wing behaviors of a rhinoceros beetle during takeoff flights

Abstract

We investigated the aerodynamic characteristics of a beetle in a takeoff flight by measuring the temporal and spatial changes in body and wing behaviors. In particular, three-dimensional trajectories and/or deformations of rigid outer wing (elytron) and highly flexible inner wing (hindwing) were measured with three high-speed cameras (at 2000 fps) and reconstructed for the analysis using a modified direct linear transform algorithm. From an inclined rod, the beetle is observed to perform a takeoff flight without the aid of legs, i.e., jumping. Although the elytron is flapped passively induced by the hindwing motion, it is found to have non-negligible flapping amplitude and angle of attack, indicating that the aerodynamic force generation by the elytron itself would be influential. Furthermore, the measured trajectories of an elytron and hindwing imply that the beetle may utilize well-known mechanisms such as a delayed stall, clapand- fling, wing-wing (elytron-hindwing) interaction, and figure-eight motion. Finally, the flexibility of a hindwing affects the heaving motion (out of the stroke plane) most significantly; i.e., the local variation of the deviation angle along the wing span is more pronounced compared to that of flapping angle and angle of attack.