Notes on the host-finding behaviour of Tabanidae (Diptera).

Tabanids that had been electrocuted [cf. RAE/B 60, 1259] while ranging in the absence of baits or when attracted by visual or olfactory stimuli from mobile and stationary objects in woodland dominated by Colophospermum mopane in Rhodesia were examined. It was found that the small catches of ranging flies contained equal numbers of the sexes, whereas the larger catches at baits contained a high proportion of females. With mobile baits (warthog and a model animal), many flies were attracted by visual stimuli, but the presence of host odour did not result in increased catches. With stationary baits, many flies were caught with a visual stimulus alone (a model animal) or with odour alone (ox and three men out of sight), but most were caught when both stimuli were presented together. Under such conditions, odour appears to induce anemotaxis from a distance, whereas visual stimuli assist final orientation. Comparison of the data for Tabanids with one of the authors’ (G.A.V.) findings on Glossina morsitans morsitans Westw. and G. pallidipes Aust. revealed points both of similarity and contrast. With Glossina, as with the Tabanids, there was no indication that odours greatly increased the attractiveness of mobile baits. Unlike Glossina, Tabanids showed no marked avoidance of human odour.