Dual functions of insect wings: balancing aerodynamics and olfaction

The ability to track odor plumes to its source (food, mate, etc.) is the key to the survival of many insects. During this odor-guided navigation, flapping wings have been speculated to actively draw odorants to the antennae and enhance olfactory sensitivity. Utilizing an in-house computational fluid dynamics solver, we have quantified the odor plume structures of a fruit fly in forward flight motion and have confirmed that the flapping locomotion induces a strong airflow vortex over its head, thereby enhancing the odor mass flux around its antennae (by ~1.8 times at its peak). Contrary to the common belief that the wing shapes of insects are optimized purely for aerodynamic performance, our results suggest that, because both aerodynamic and olfactory functions are indispensable during odor-guided navigation, the wing shape and size may be a balance between the two functions. Furthermore, we found that the increased odor mass flux is the result of broader spatial sampling range in the vertical direction below the body, but not horizontally. This anisotropic spatial sampling range may also have important implications in understanding the behavior and algorithm of plume tracking in insects.