Carbon dioxide-baited traps and bird-associated odors: Orientation behavior and chemical ecology of host-seeking Culex mosquitoes

The orientation behavior of two species of ornithophagous mosquitoes, Culex pipiens quinquefasciatus Say and Culex tarsalis Coquillett, was examined while approaching CO2-baited mosquito traps in a field wind tunnel. The four traps used in this study were the Centers for Disease Control (CDC) style trap, the Mosquito MagnetRTM Freedom (MMF), Mosquito Magnet Liberty (MML), and the Mosquito Magnet-X (MMX). The plume structures of these traps was examined, as well as other differences which might lead to differential capture rates. The MMX trap was the most efficient of the four traps. Mosquitoes oriented straight upwind until they reached within about 30 cm from the traps, at which point their flight paths became increasingly tortuous, indicating a shift in orientation strategy. Approaching mosquitoes were found to fly past the essentially transparent MMX trap, whereas they flew to the main bodies of the other three traps. It was suggested that the use of visual cues takes precedence over upon coming within close range of the traps, and the lack of visual cues allows more mosquitoes to orient to the odor source. Augmenting CDC-style traps so that the odor source was closer to the trap entrance improved trap captures in the field. Mosquitoes were also found to fly upwards in response to changing visual cues. Acidified chicken feces was elicited attraction of C. p. quinquefasciatus females in the absence of CO2. Eight novel host-associated odors were identified from chicken feces and found to elicit antennal responses in electroantennograms of C. p. quinquefasciatus females, all of which were aldehydes. An improved technique for electroantennograms is proposed in which four antennae are tested simultaneously.