Field sampling of unfed adults of Amblyomma hebraeum Koch.

No methods have previously been available for the field sampling of unfed adults of Amblyomma hebraeum. We released 2000 unfed adults into a 5-m2 area in mopane woodland in southeastern Zimbabwe. The ticks sought shelter beneath the debris on the soil surface but emerged and became active in host seeking when stimulated. Effective stimuli were the odours of cattle and sheep and high concentrations of carbon dioxide from dry ice. The ticks did not respond to low concentrations of carbon dioxide, vibrations generated by stamping the ground with poles, or two volatile components of ox breath known to attract tsetse flies. The presence of humans in the release area also had little or no effect in stimulating the ticks. As adults of A. hebraeum are large and conspicuous they can easily be collected from the soil surface, either manually or using a vacuum device, after stimulation by cattle or the release of high concentrations of carbon dioxide.