Do tsetse flies ‘see’ zebras? A field study of the visual response of tsetse to striped targets
1992
GIBSON, GABRIELLA
A field study in Zimbabwe of Glossina pallidipes Austen and G. morsitans morsitans Westwood supported Waage's (1981) hypothesis that the striped pattern of zebras may protect them from being bitten by blood‐sucking flies. In addition, the results suggest that the orientation of the stripes may be crucially important for the unattractiveness of zebras. The relative attractiveness of five different stationary targets (black, white, grey, vertically‐striped and horizontally‐striped; stripe width = 5 cm) were each tested on their own and in pairs of all combinations, with artificial host odour (CO2 plus acetone) always present. Electric nets were used to catch flies as they attempted to land on or circle the targets. The results were similar for the two species of tsetse. When tested on their own, grey and vertically‐striped targets caught similar numbers of flies and both caught significantly fewer than black or white targets (c. 36% as many). Horizontally‐striped targets caught <10% as many flies as any other single target. Although there was no significant difference between the attractiveness of grey and vertically striped targets when they were presented together, when paired with the other targets, grey was as attractive as black or white, but the vertically‐striped target was significantly less attractive than black or white (P < 0.001). In other words, a difference between grey and vertical stripes was found only in their attractiveness in relation to other targets. The horizontally‐striped target, however, always caught the fewest flies, regardless of whether it was presented alone or alongside another target.
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