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Cows might seem harmless, but their breath can actually be deadly—for mosquitoes, that is. In some Florida locales swarming with mosquitoes, officials are using a concoction of carbon dioxide and the chemical octenol, which resembles bovine exhalations, to attract and trap the insects in a death chamber.

In some areas, they use the traps instead of spraying insecticides over breeding grounds, like marshes or wetlands; in others, experts employ them to gauge populations and whether spraying is needed.

“The traps don’t harm the environment—that’s one of the appealing factors,” says . Mosquitoes are opportunistic, he explains, and dine on a number of hosts besides cows, including reptiles, horses, and people, so it can be difficult to trick them, but the traps work against many of the 2,900 known mosquito species.

This story originally ran in the July-August 2009 issue as "Fatal Attraction."