Should you trap or zap? (Mosquito traps * Test).(Buyers Guide)

A repellent may work on the person wearing it, but what if you want to ban mosquitoes from a whole area, so, say, they won't crash your backyard barbecue? Bug zappers, the ultraviolet-light devices that slay insects with a reassuring "zot!" are one option. In our tests, however, a zapper killed barely more mosquitoes than lodged on a nearby piece of sticky paper.

A newer choice: traps that lure and capture mosquitoes by mimicking mammals. The three widely sold traps we tested were not a cure-all. Although they were far more effective than the zapper at removing mosquitoes we released into a lab room, they didn't eliminate all of them. A species that carries West Nile virus was only moderately attracted.

In the end, we had to agree with Ray Parsons, director of mosquito control for Harris County, Texas, site of a large West Nile virus outbreak. "They do pull in lots of mosquitoes," Parsons told us, "but people shouldn't expect them to reduce the potential of disease transmission completely."

How they work. Traps mimic factors that make people irresistible to mosquitoes: exhalations, odors, body heat, or sound. Once they've lured the bugs--from a claimed area of 3/4 acre or 1 acre, depending on the model--they use either suction or sticky paper to capture them. The traps we tested must be plugged into an electrical outlet, and manufacturers advise using them around the clock during mosquito season, rain or shine.

The American Biophysics Mosquito Magnet Liberty, $500, and the Lentek Mosquito Trap MK01, $325, generate carbon dioxide and warmth by burning propane from a standard 20-pound tank that must be purchased separately. The Magnet Liberty also includes a cartridge of octenol, a chemical attractant said to smell--to a hungry mosquito, at least--like cow's breath. Both traps have fans that suck approaching mosquitoes into a mesh bag or cup, where they stay because they can't fly "upwind." (They then dehydrate and die.) The Magnet Liberty's fine-mesh bag should also capture no-see-urns and other tiny biting insects; the larger holes in the Trap MK01's cup or bag (both are included) may let some slip through. The Applica SonicWeb ICH500, $300, has a small loudspeaker that generates the sound of a heartbeat. A plastic frame surrounding the speaker includes an electric heating element, a hook for hanging an octenol lure, and a cylinder that holds a sticky paper sleeve that captures mosquitoes only if they land on it.

How we tested. We released a couple thousand mosquitoes into a 25-by-30-foot sealed room with a trap at one end. About half were Culex quinquefasciatus, a species that has helped spread West Nile virus into the southern U.S. (Culex pipiens, a close relative with almost identical habits, is mainly to blame for the outbreak in the North.) The rest were Aedes aegypti, a common southern species that's especially tenacious in its pursuit of people.

We ran each trap for 20 hours, half of that time in the dark, then recorded the number and species of mosquitoes caught in each device.