Insect wings do not contain intrinsic musculature to change shape, but rather bend and twist passively during flight. Some insect wings feature flexible joints along their veins that contain patches of resilin, a rubber-like protein. Bumblebee wings exhibit a central resilin joint (1m-cu) that has previously been shown to improve vertical force production during hovering flight. In this study, we artificially stiffened bumblebee (Bombus impatiens) wings in vivo by applying a micro-splint to the 1m-cu joint, and measured the consequences for body stability during forward flight in both laminar and turbulent airflow. In laminar flow, bees with stiffened wings exhibited significantly higher mean rotation rates and standard deviation of orientation about the roll axis. Decreasing the wing's flexibility significantly increased its projected surface area relative to the oncoming airflow, likely increasing the drag force it experienced during particular phases of the wing stroke. We hypothesize that higher drag forces on stiffened wings decrease body stability when the left and right wings encounter different flow conditions. Wing splinting also led to a small increase in body rotation rates in turbulent airflow, but this change was not statistically significant, possibly because bees with stiffened wings changed their flight behavior in turbulent flow. Overall, we found that wing flexibility improves flight stability in bumblebees, adding to the growing appreciation that wing flexibility is not merely an inevitable liability in flapping flight, but can enhance flight performance.
The authors declare no competing or financial interests.
E.A.M. carried out data collection and analyses, and drafted the manuscript. A.M.M. and S.A.C. performed data analyses. All authors participated in the design of the study and drafting of the manuscript, and gave final approval for publication.
This work was supported by National Science Foundation grants IOS-1253677 and CCF- 0926158 to S.A.C., and by Harvard College Research Program and Museum of Comparative Zoology Grants in Aid of Undergraduate Research to E.A.M.
- Received October 10, 2015.
- Accepted August 17, 2016.
- © 2016. Published by The Company of Biologists Ltd