Host preferences and discrimination by the mosquitoes Aedes aegypti and Culex tarsali (Diptera: Culicidae).

Abstract

An experimental cage with a revolving turntable is described which permits host preference studies to be conducted in the laboratory and which yields results agreeing with field studies. The size and composition of the test population can be controlled, and conditions standardized, providing advantages over field studies. Using this experimental cage and sticky type traps, it was shown that Aedes aegypti (L.) preferred mice to chicks regardless of the weight ratio, while Culex tarsalis Coquillett only preferred the chicks when their weight was 2× that of the mice, otherwise showing no preference. C. tarsalis was attracted to frogs, toads, and lizards, but preferred mice or chicks. A. aegypti was not attracted to cold-blooded animals. A freeze trapping technique for the collection of animal odors which enables nonchemical separation of odor from carbon dioxide is described. Using this technique, it was found that chick and mouse odor is attractive to both species of mosquitoes, but that live mice are preferred to mouse odor. Human odor from the forearm is as attractive to A. aegypti as baby chick odor. No attractive odor from frogs or lizards was found. The mosquitoes were unable to distinguish mouse odor from chick odor when present in equal amounts. With all other factors being equal, the mosquitoes preferred whichever odor was the most abundant. The addition of CO2 to mouse odor increased its attractiveness to A. aegypti . No preference was shown by A. aegypti for either mouse odor plus mouse amounts of CO2 or chick odor phis chick amounts of CO2. The carbon dioxide with the chick odor was released at a rate 2.5× faster than that with the mouse odor. For A. aegypti CO2 is attractive, but once a low threshold level of CO2 is reached the addition of more does not cause increased attraction.