Mosquito bites aren't just an annoyance, they can be deadly. Mosquitoes transmit serious diseases, from malaria to West Nile virus. If you're planning to spend any time outdoors, you should protect yourself from mosquito bites. Many people hang insect electrocution lights, or bug zappers, in their backyards to kill biting insects. But do bug zappers actually kill mosquitoes? Here's what you need to know about bug zappers and mosquitoes.
What Are Bug Zappers?
Bug zappers attract insects using ultraviolet light. The light fixture is surrounded by a mesh cage, which is energized with a low voltage current. Insects drawn to the UV light attempt to pass through the electrified mesh, and are subsequently electrocuted. Most bug zappers are designed with a collection tray, where the dead insects accumulate.
Why Mosquitoes Bite
Female mosquitoes require the protein from blood to develop their eggs, and in most cases, they need mammalian blood. However, not all mosquitoes bite us. Some mosquito species prefer avian blood, and others specialize in reptile or amphibian blood sources. A few species can develop eggs without blood at all; these mosquitoes use the sugar from plant nectars instead. And of course, male mosquitoes don't require blood meals, since they aren't incubating eggs. Before you condemn the entire mosquito family, remember that mosquitoes serve an ecological purpose. They aren't just out to get you!
How Mosquitoes Find Blood
When evaluating mosquito control products, it's important to understand how mosquitoes locate a source of blood. In other words, think about how the mosquito finds someone to bite. Regardless of whether they're human, canine, equine, or avian, what do all living blood sources emit? Carbon dioxide! Mosquitoes, like most biting insects, can home in on the scent of carbon dioxide in the air. Research suggests a bloodthirsty mosquito can detect carbon dioxide from as far as 35 meters away from its source. At the slightest hint of CO2, the mosquito will being flying in zigzags, using trial and error to pinpoint the person or animal in the area. Carbon dioxide is the most powerful attractant for mosquitoes. Mosquitoes also use other scent clues to find people to bite. Perfume, sweat, and even body odor can attract mosquitoes.
Bug Zappers Don't Attract Mosquitoes, Carbon Dioxide Does
Think about it. Bug zappers attract insects using ultraviolet light. Mosquitoes find their blood meals by following the trail of carbon dioxide. Does that mean bug zappers never kill mosquitoes? No, of course not. Occasionally, a mosquito will get curious about the pretty light and make the fatal mistake of getting too close. But there's no guarantee that mosquito is even a female, and therefore a biting mosquito. Anyone with a basic understanding of mosquitoes will surely conclude that a bug zapper isn't the best choice for mosquito control. But don't take my word for it. Let's see what the research says.
Research Proves Bug Zappers Are Ineffective for Killing Mosquitoes
In 1977, researchers from the University of Guelph conducted a study to determine how effective bug zapper products are at killing mosquitoes and reducing mosquito populations where they are used. They collected dead insects from bug zappers in people's backyards, and found that just 4.1% of the insects killed in the bug zappers were female (and therefore biting) mosquitoes. That means a full 95.9% of the insects killed were not biting mosquitoes. The study also found the yards with bug zappers had higher numbers of female mosquitoes than those without bug zappers.
Notre Dame researchers conducted a similar study in 1982, with similar results. They tallied the kills from bug zappers in backyards in South Bend, Indiana, where mosquito populations were moderate to high. In an average night, a single bug zapper killed 3,212 insects, but only 3.3% of the dead insects were female mosquitoes. So almost 97% of the insects killed in these backyards were not biting mosquitoes. In addition, these researchers found that people in backyards with bug zappers were consistently more attractive to mosquitoes. The UV light seemed to draw more mosquitoes to those backyards, where the mosquitoes would then follow the carbon dioxide trail to their victims. The Notre Dame scientists noted that even when a bug zapper was kept on for 11 days, it failed to reduce the number of biting mosquitoes in the homeowner's backyard.
In 1996, researchers at the University of Delaware tallied an entire summer's worth of dead bugs from bug zappers in their study. Of a total of 13,789 insects killed in the bug zappers, a paltry 0.22% of them were biting mosquitoes or gnats. Just 31 insects out of almost 14,000! This study took the research a step further, and reported the incidence of beneficial insects killed. Almost half of the dead insects (6,670, or 48.4%) were harmless, aquatic insects, important food for fish and other stream inhabitants. A significant number of beneficial predators and parasitic insects were also killed in the bug zappers (1,868, or 13.5%). These insects help control pest insect populations, meaning bug zappers could actually make pest problems worse.
Scientists at the UF/IFAS Florida Medical Entomology Laboratory in Vero Beach, FL, also examined the effectiveness of bug zappers in 1997. A single bug zapper in their study killed 10,000 insects in one night, but just 8 of the dead bugs were mosquitoes.
But My Bug Zapper Kills Mosquitoes!
When I've blogged about the ineffectiveness of bug zappers in the past, readers have commented and emailed me to dispute this assertion. Despite all the research that proves otherwise, people who use bug zappers insist that they see "lots of mosquitoes" dead in their zapper's collection tray. And they hear that satisfying sizzle when bugs get fried – it must be working, right?
I have no doubt that your bug zapper kills a lot of insects, and that many of the insects you find lying dead in the zapper look like mosquitoes. The problem is, they're not mosquitoes. They're midges. The research shows that non-biting midges, which look very much like their mosquito cousins, are highly attracted to lights and will fry themselves in bug zappers in large numbers. Most homeowners can't differentiate midges from mosquitoes when examining the hundreds of dead carcasses piled up in the bug zapper.
Study after study has proven that bug zappers do very little or nothing at all to put a dent in the biting mosquito population. On the other hand, limiting mosquito breeding habitat and using appropriate mosquito deterrents like DEET does protect you from mosquito bites, and from the diseases mosquitoes carry.
1Surgeoner, G. A., and B. V. Helson. 1977. A field evaluation of electrocutors for mosquito control in southern Ontario. Proc. Entomol. Soc. Ontario 108:53-58.
2Nasci, RS, CW. Harris and CK Porter. 1983. Failure of an insect electrocuting device to reduce mosquito biting. Mosquito News. 43:180-184.
3Frick, TB and DW Tallamy. 1996. Density and diversity of nontarget insects killed by suburban electric insect traps. Ent. News. 107:77-82.
4 University Of Florida, Institute Of Food & Agricultural Sciences, 1997. "Snap! Crackle! Pop! Electric Bug Zappers Are Useless For Controlling Mosquitoes, Says UF/IFAS Pest Expert" Accessed September 4, 2012.