Building a Better Mosquito Trap

UC Davis scientists who have been sussing out mosquitoes' sniffers have made a discovery that could lead to really killer bug traps. Chemical ecologists Walter Leal and Zain Syed identified a chemical called nonanal in humans—and, crucially, birds—that serves as a signal for the Culex species of mosquito. Nonanal is a metabolic product of fatty acid, and while it's unclear what its function is for us, for hungry mosquitoes it's like a "BITE HERE" sign. The scientists tested hundreds of compounds that birds and humans have and found that sensitive mosquito antennae can detect even minute amounts of nonanal. They used the chemical as a lure and waited to see how bloodsucking, West-Nile-Virus carrying Culex mosquitoes would react. Leal says when they added carbon dioxide to nonanal, the combo attracted more mosquitoes than each of them combined. A heavy duty CO2 trap they put in nearby Yolo County caught around 2,000 of mosquitoes nightly. Leal says synthetic nonanal is dirt cheap to produce and he thinks that traps with it might be available next year. Next, the plan is to test other mosquito species' responses to the combo. Sadly, an effective DEET alternative is still elusive. Blocking nonanal and CO2 means mosquitoes will find a different signal, Leal reports. He also told me that if he had an effective repellent that decreased human attraction to mosquitoes, he'd be first in line. "They give me a tremendous allergic reaction." Photo: UC Davis chemical ecologists Walter Leal (left) and Zain Syed in the lab. Credit: Kathy Keatley Garvey/UC Davis Department of Entomology. en tested for safety on humans, he noted.