Quantitative Field Studies on a Carbon Dioxide Chemotropism of Mosquitoes

W. C. ReevesThe George Williams Hooper Foundation for Medical Research, School of Public Health, University of California, San Francisco

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Carbon dioxide, released at rates of approximately 25 ml., 250 ml. and 2,500 ml. per minute, was successfully employed as a host-simulating mosquito attractant. These rates were selected because they represent approximately the average amounts of carbon dioxide given off by chicken, man, and horse or cow, respectively.

Large numbers of female mosquitoes of several species were attracted into traps baited with these concentrations of carbon dioxide. The various species of mosquitoes responded differently. Aedes nigromaculis was attracted in the greatest numbers to the higher concentrations. More Culex quinquefasciatus were attracted to the least amount. Culex tarsalis was greatly attracted to all three concentrations, but the largest numbers were attracted to the traps where the rate of release was highest. These observations are correlated with available knowledge of the host preference habits of these species and they suggest a direct interrelationship of host-seeking and carbon dioxide chemotropism.

These observations are of potential value in epidemiological studies of mosquito-borne diseases and offer a new investigative tool in such research.