Three‐dimensional flight tracking shows how a visual target alters tsetse fly responses to human breath in a wind tunnel

Tsetse flies Glossina spp. (Diptera; Glossinidae) are blood‐feeding vectors of disease that are attracted to vertebrate hosts by odours and visual cues. Studies on how tsetse flies approach visual devices are of fundamental interest because they can help in the development of more efficient control tools. The responses of a forest tsetse fly species Glossina brevipalpis (Newstead) to human breath are tested in a wind tunnel in the presence or absence of a blue sphere as a visual target. The flight responses are video recorded with two motion‐sensitive cameras and characterized in three dimensions. Although flies make meandering upwind flights predominantly in the horizontal plane in the plume of breath alone, upwind flights are highly directed at the visual target presented in the plume of breath. Flies responding to the visual target fly from take‐off within stricter flight limits at lower ground speeds and with a significantly lower variance in flight trajectories in the horizontal plane. Once at the target, flies fly in loops principally in the horizontal plane within 40 cm of the blue sphere before descending in spirals beneath it. Successful field traps designed for G. brevipalpis take into account the strong horizontal component in local search behaviour by this species at objects. The results suggest that trapping devices should also take into account the propensity of G. brevipalpis to descend to the lower parts of visual targets.     

Complex NAPL Site Characterization Using Fluorescence Part 1: Selection of Excitation Wavelength Based on NAPL Composition

Fluorescence has been demonstrated to be a viable method for detecting non-aqueous phase liquid (NAPL) contaminants comprised of polycyclic aromatic hydrocarbons (PAHs). Commercially available cone penetrometer (CPT)induced fluorescence based sensor platforms can be used to detect NAPLs such as petroleum oils and lubricants in-situ. In addition, these approaches can be used to detect dense non-aqueous phase liquid (DNAPL) source zones by detecting commingled oils, fuels, and naturally oc curring organic materials entrained by or in solution with DNAPLs and carried to depths below the water table. The currently available CPT-based fluorescence systems are typically restricted to a single wavelength excitation source, each demonstrating specific advantages and disadvantages with respect to detection capabilities for partic ular fluorophores. Several neat NAPLs and mixtures were analyzedfor specificfluores-cence characteristics to determine the optimal excitation source for site characterization efforts. Commercially available cone penetrometer based fluorescence detection systems were ranked according to the potential for likelihood of detection. Our work demon strates that an optimal range of excitation wavelength can be determined for specific fluorophores within NAPL mixtures, and that available systems can be ranked based on the specific contaminant and site characteristics. We have identified optimal excitation sourcesfor a number of common NAPL mixtures, including petroleum-basedfuels and a lubricant mixed with a chlorinated solvent.