Effects of flight speed on olfactory sensitivity in upwind surging flights of a hawkmoth

In nature, flying insects rely on odor-guided navigation to perform a variety of tasks, including finding mates, locating food, and detecting predators. Their flapping wings can potentially draw more odor plumes towards their antennae, thereby enhancing their olfactory sensitivity. However, insects’ flapping wing kinematics drastically change as flight speed increases. It is unclear how varying an insect’s flight speed impacts its odorant perception. In this study, we reconstructed wing kinematics of a hawkmoth at both 2 m/s and 4 m/s using high-speed video recordings. Then, CFD simulations were adopted as a non-intrusive approach to investigate the unsteady flow field by solving the Navier-Stokes equations and the odorant transport process by solving the advection-diffusion equations. Results show that hawkmoths use their wings to increase the odor intensity around their antennae. At both flight speeds, odor intensity is enhanced and synchronized with the flapping motion. Compared with the 4 m/s case, the peak odor intensity is approximately 39% higher during the 2 m/s flight. We suspect that lower flying speed can enhance the olfactory sensitivity of hawkmoth in odor-tracking flights.