Fig. 2. (A) Landmarks on forewing and hindwing of a dragonfly; (B) definition of the local body-centered coordinate system and yaw, pitch and roll angles. Arrows define the positive rotation directions. The local body-centered coordinate system O'X'Y'Z' is based on four wingbases (B1, B2, B3 and B4), where points B1 and B2 are wingbases of the forewing, and B3 and B4 those of the hindwing. The midpoint K_F of B1 and B2 is the origin of the local body-centered coordinate. The Y'-axis is along the line K_FK_H that joins points K_F and the midpoint of B3 and B4, K_H. The plane X'O'Y' is constructed by points K_F, K_H and B1. The Z'-axis is perpendicular to the X'O'Y' plane and upward.