Olfactory conditioning of Anopheles dirus (Peyton & Harrison 1979) (Diptera: Culicidae) to a sugar-meal

Within the Culicidae, laboratory evidence has been collected for associative learning between adult Culex and Aedes mosquitoes and odors coupled with oviposition sites, blood meals and sugar sources. Many observations obtained through field studies have documented home ranges and localized host preferences in mosquito populations which have the potential to be explained through an associative learning process. This investigation presents the first evidence that an anopheline mosquito is capable of associative learning using a classical conditioning approach. The Anopheles dirus complex contains some of the most important malaria vectors in Southeast Asia. The importance of associative learning processes in significant vector species and the extent to which these processes affect disease transmission cycles has yet to be examined and research in this area may lead to a better understanding of disease transmission. In this study we conditioned An. cracens males and females, 3-5 days old, to the odor of myrcene using three training trials of odor exposure coupled with a partial 10% sucrose meal. The following day (21-24 hrs later) conditioned mosquitoes were exposed to one of three tests to evaluate their responses to an odor free control, the odor of myrcene or the odor of geraniol, with which they had no previous exposure. Responses were recorded as binary data (positive/negative) and analyzed with binary logistic regression to evaluate differences in response. Males show clear evidence of learning whereas females do not. Differences inherent to the physiology and ecology of the sexes could provide explanations for this apparent learning dichotomy.