Meeting Abstract

P2.75  Monday, Jan. 5  Pterostigma regulates the dynamic properties of dragonfly wings CHI, K. -J.*; CHANG, C. -T.; TSAI, F. -Y.; SHIH, M. -C.; National Chung-Hsing University; National Chung-Hsing University; National Chung-Hsing University; National Chung-Hsing University kjchi@phys.nchu.edu.tw

The pterostigma of insect wings, usually a pigmented spot, locates close to the leading edge far out on the wing. Our measurements show that in dragonfly, pterostigma accounts for merely 0.5% of the wing area, yet weights for more than 2.5% of wing mass without the enframing vein. Such concentration of mass suggests it may affect the dynamic properties of the wing during flapping. Previous study suggests pterostigma an inertial regulator of wing pitch to raise the gliding speed limit, at which self-excited vibrations would otherwise occur without this mass. However, no empirical evidence is provided to date. In this study, we examine the effects of pterostigma on the dynamic characteristics of isolated dragonfly wings under forced vibration. To quantify the deformation of the wing, the relative positions of the base, nodus, and pterostigma of the wing were measured. Our data reveal that the existence of pterostigma does change the wing’s oscillating distortion mode during flapping. After the pterostigma was removed, the oscillating amplitude of wing deformation decreases, yet the resulting fluctuation increases. These results suggest that pterostigma may magnify the deformation of the wing, while stabilize its oscillation mode. Furthermore, we find a phase difference occurred between the stabilized mode and the driven flapping. This phase shift may have mechanical consequences on the flight of dragonflies.