Kinetics of elastic recoil in the wings of the cicada, Dundubia rufivena

In this paper, we quantitatively characterise the kinetics of elastic recoil in the wings attached to the cicada Dundubia rufivena.We use high-speed videography to deduce the velocities of recoil motion in both bending (B) and torsion (T), in downstroke and upstroke modes of flapping. Elastic recoil is faster in downstroke (DS) than it is in upstroke (US), reaching average velocities, ̄v, 244 ◦ ⋅ s−1 in DS-B versus 6434 ◦ ⋅ s−1 in US-B, and 5887 ◦ ⋅ s−1 in DS-T versus 4545 ◦ ⋅ s−1 in US-T. Our results also therefore evidence that bending velocities during elastic recoil are higher than the velocities in torsion, and conclude that this is a result of the necessary geometrical distances that need to be covered over a stroke. The wings do not act alone as biological springs, but rather, we find that the stiffnesses of the wings (1.7–3.6 GPa) are higher when attached to the cicada body than they are when detached. This evidences thoracical involvement as part of the biological spring enabling elastic recoil, indicating that elastic recoil of flapping wings should be approached from a systems perspective, rather than solely through a localised understanding of wing mechanics.