Dragonfly (Sympetrum flaveolum) flight: Kinematic measurement and modelling

• The kinematics of the wing is studied thoroughly using high-speed videography.
• The costa is shown to be two parts hinged with physical constraint of forty degrees.
• Two flapping patterns are revealed: simple figure-eight and a double figure-eight.
• Kinematic modelling is established.
• Previous misunderstandings regarding the wing rotation during pronation are clarified.

The kinematics of the flapping hindwing of the dragonfly Sympetrum flaveolum is investigated. Several tracking points along the leading edge and trailing edge of the hindwing are recorded and studied using high-speed videography. By applying more tracking points along the leading edge around the nodus, it is shown that the leading edge is not one rigid piece, but two pieces hinged at the nodus with physical constraint of forty degrees. Such arrangement also eases the difficulties in rotating the wing during pronation by bending the leading edge forward and flattening the wing. From the kinematic experiments, two flapping patterns of the dragonfly wing are revealed as a simple figure-eight and a double figure-eight flapping pattern. Kinematic modelling of the two flapping patterns is then established by transforming the flapping motions into angular rotations about the pivoting wing root in a local body-fixed spherical coordinate system.