Meeting Abstract
The odor signal detected by a plume tracking animal results from the interaction of: 1) environmental turbulence flowing over the odor source, 2) the size, shape and position of the odor sensors on the tracker’s body, and 3) the form of locomotion used by the tracker. The flapping wings of flying insects generate an additional directional flow, usually from head-to-tail over the animal. Depending on the speed of the wind in which they are flying, this wing-beat induced flow can account for nearly 100% of the flow over the odor-detecting antennae (i.e., hovering or experimentally tethered). To better characterize wing-beat induced flows and how they might influence detection of the odor plume, we used a hot-wire anemometer to measure the wing-beat induced flows near the antennae of tethered flying Manduca sexta moths across a range of wind speeds. Wing beat induced flows can be divided into two components, 1) the mean flow, or average flow speed from front-to-back over the moth, and 2) the periodic flow, or the regular rhythmic increases and decreases in flow caused by the up and down stroke of the wings. As would be expected, the mean induced flow increased each time we increased the wind speed. Thus, the moth was always generating flows that were slightly faster than the wind speed. The periodic flow accounted for 100% of the induced flow in still air. As the ambient wind speed increased, the proportion of the flow over the antennae accounted for by the periodic wing beat induced flow decreased. The range of wind speeds where the influence of the periodic component of the induced flow is strongest coincides with the range of wind speeds most likely to be encountered by these moths during their activity periods in nature. Electrophysiological recordings from the antennae show the effect of wing beat induced flows on the plume structure detected may be fairly subtle.
