Chemo-orientation in Flying Insects

Our perceptions of the maneuvers and sensory inputs that animals employ to locate a stimulus have undergone continued refinement and reformulation following the efforts of Loeb (1918) and Kuhn (1919) to classify orientation mechanisms. The adduction that the principal mechanism of ‘long-distance’ flying orientation to an airborne chemical stimulus in the wind is an optomotorguided, chemically-induced, upwind orientation (or anemotaxis) has gained wide acceptance as a considerable body of experimental evidence in support of this mechanism has accumulated, principally with moth attraction to upwind pheromone sources. Besides optomotor anemotaxis, a number of alternative tactics have been proposed; these strategies have posited the existence of either spatial or temporal distributions of chemical stimulus that, if recognized, could serve as cues to guide the responder toward the chemical source or, if not to supply cues as to its direction, at least provide information as to its proximity. But our current understanding of the ‘instantaneous’ structure of a chemical stimulus emanating from a point source in continual or intermittent wind is imperfectly developed (see Elkinton and Carde, Chapter 3) and this limits our ability to hypothesize intelligently on alternatives to the upwind anemotaxis paradigm.