CO2 mosquito trap
Photo: Frontgate
To intercept mosquitos before they spot human prey, the new CO2 traps should be placed at least 30 feet away from places where people gather.
In times past, homeowners dispatched mosquitoes with a well-aimed swat of the hand, or tried to banish them with a spritz of insect repellent and maybe a citronella candle.

Not anymore. As the risk of mosquito-borne illnesses such as West Nile virus and even malaria has spread to the United States, bug killing has become serious business. These days, there's a new weapon in the arsenal: high-tech traps that lure mosquitoes to their death by mimicking the breath, scent, and body heat of humans.

The chief chemical attractant is carbon dioxide, which we give off by breathing and which traps generate with a CO2 canister or by burning propane. The burning propane also produces heat and water vapor, similar to human sweat. In addition, the traps emit octenol, an aroma that mosquitoes can't resist. When they draw near to investigate the plume of octenol-laced CO2, they're either sucked into a net, become stuck to an adhesive pad, or are zapped by an electric charge. According to manufacturers, some of these devices are so effective that they can clear an area of up to an acre.

Safer Than Pesticides, Better Than Zappers

Compared with fogging a landscape with insecticides, these new traps are benign and nontoxic, harming only mosquitoes and other flying biters, such as blackflies and biting midges. And they're a quantum leap better than electric bug zappers that use light as an attractant, which are ineffective against mosquitoes. Tests in mosquito-infested areas show that a single CO2 trap can nab as many as 1,500 bloodsuckers in one evening. "Those things do attract and kill a lot of mosquitoes — no question about it," says Jerome Goddard, Ph.D., a medical entomologist at the Mississippi Department of Health.

Whether that will keep you from getting bitten depends on how many mosquitoes are hatching in your vicinity. "What nobody knows is whether these traps cause the population to drop," says Goddard. "It could be like dipping a bucket of water out of the ocean." Because mosquito populations vary dramatically from day to day and even house to house, scientists say, it's tough to design a reliable test that shows which of these devices works best.

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