Effect of adding the Mbita odour blend to carbon dioxide produced by fermentation of 250 g (panel A) and 500 g (panel B) molasses on the mean number (±SE) of Anopheles gambiae collected for four nights. A total of 200 female An. gambiae were released per night within a screen-walled greenhouse. Bars with different letters in the same graph differ significantly (P <0.05). Error bars represent the standard error of the mean number of mosquitoes collected.