Sampling Adults with Carbon Dioxide Traps

As early as 1922 Rudolfs reported that carbon dioxide was an attractant for mosquitoes, and that carbon dioxide produced by breathing was an important factor in attracting mosquitoes to their hosts. It is now generally accepted that carbon dioxide is, in concert with other olfactory cues, an attractant to virtually all haematophagous flies. In most of the West African species studied by Gillies and Wilkes (1969) carbon dioxide was a middle range factor in host orientation, activating and attracting mosquitoes from about 15–30 m, but the actual distance over which it acted depended on the species. Ornithophagic species appeared to be little attracted by carbon dioxide (Gillies and Wilkes 1972). In later trials Gillies and Wilkes (1974), using ramp traps, found that whereas birds attracted Anopheles melas and Culex thalassius from at least 7 m, carbon dioxide (50 ml/min) attracted these ornithophagic species from up to only 4 m. In contrast, in Uganda Henderson et al. (1972) caught large numbers of ornithophagic mosquitoes in CDC light-traps when they were supplemented with dry ice, seemingly indicating that carbon dioxide was an important attractant.