DAVIS, E.C.*; LOUDON, C.: Distortion of a chemical plume by a pectinate antenna

As animals sense the environment around them, they decipher spatially-complex chemical stimuli, such as sex pheromones. The spatial complexity of a chemical stimulus is modified as the chemicals are transported over distances prior to detection. The ability of insects to detect sources of chemicals over long distances (> 10 m) is well-established. More recently it has been demonstrated that fine-scale (mm’s) spatial heterogeneity of a chemical plume is perceptible to some insects. The detection of a chemical stimulus by chemosensory hairs on an insect antenna is affected by the air flow pattern adjacent to the sensory structures. In particular, pectinate (feathery) antennae typically process only a small fraction of the oncoming chemical-containing air, which leads to flow diverging at the antenna. Using a flow visualization technique, we illustrate how the properties of diverging flow expected for pectinate insect antennae will affect both the sensitivity and the modification of the spatial heterogeneity of the chemical stimulus. Supported by NSF grant IBN-9984475 to CL.