Fig. 4. Fine-scale odor structure along the antennule during flicking (C), normalized by source concentration (C_source). (A) Odor concentration along the antennules as a function of time in wave-affected flow. (B) Similar information from a successful track in unidirectional flow. These panels show the odor concentration along each antennule during flicking, which is when the animal samples odors. Each vertical bar indicates a flick. In most cases, a flick lasts one frame only, but in six cases, the flick takes two frames to complete. The top portion of each panel shows odor concentration along the left antennule, and the bottom portion shows odor concentration along the right antennule during the same successful track. Only odor structure encountered by the outer portion of the antennule (where the aesthetascs are located) is shown. The odor concentration is color-coded; red indicates background levels, yellow indicates low concentration, and blue indicates high concentration.