The responses of Anopheles gambiae, and other mosquitoes in Burkina Faso, to CO2—the start of a search for synthetic human odour

When two odour-baited entry traps were placed side-by-side, one emitting just CO2 and one emitting the same concentration of CO2 plus human odour, the only mosquito species showing a ‘preference’ was Anopheles gambiae s.l., 66% of which chose the human odour. When the traps were placed about 20 m apart, CO2 alone caught less An. gambiae s.l., An. funestus and Mansonia uniformis (50%, 40% and 66% of the human-odour catches, respectively) but twice as many An. pharoensis. When CO2 doses were varied, all species gave similar dose-response curves hut the behaviour of each was seen to differ when the catches were compared with those on human bait. Anopheles arabiensis chose CO2-baited traps with a higher probability than An. gambiae s.s., supporting the theory that An. arabiensis is less anthropophilic.