Friday, February 28, 2014

How Mosquito Magnets Work

There's ­no doubt about it -- mosquitoes are a total pain. They land on you, bite you, suck out some blood and leave behind an itchy welt. In the United States, however, the rise of West Nile Virus has moved mosquitoes from the "simply annoying" list onto the "danger" list, and they are now something to be feared. Disease danger has always been the case in tropical regions, where the main mosquito-borne parasite is malaria.

There are different ways to control mosquitoes. You can stay indoors (but what fun is that?). You can use DEET, but it is a smelly bother to keep applying it. You can try using things like citronella candles or torches to confuse the mosquito's sensors. What if, instead, you wanted to get rid of mosquitoes for good?
The way to eliminate mosquitoes permanently would be to kill all the mosquitoes in an area. That way, there are no more mosquito eggs being laid and thus no new mosquitoes. To kill all of the mosquitoes, you would need to devise the world's best mosquito trap. In this article, we will discuss the elements of the ideal mosquito trap and learn how a commercially available mosquito trap like the Mosquito Magnet® works.

DIY Mosquito Trap
If you ignore the fact that mosquitoes are so annoying and dangerous, they really are amazing creatures. Female mosquitoes must find blood in order to reproduce, so mosquitoes come equipped with finely tuned sensors to help them locate the blood they need. With these sensors, mosquitoes can detect carbon dioxide, warmth, certain plant chemicals and sometimes even sweat chemicals. Using these sensors, a mosquito can hone in on a mammal very easily. To learn more, see How Mosquitoes Work.
One easy way to create a mosquito trap would be to take a cow and place it in your yard. The cow would act as the attractant for the mosquitoes, because the cow would give off the chemical signature that mosquitoes crave. A cow is warm, it releases certain plant chemicals (because it eats grass all day) and it produces carbon dioxide with every breath. If you had a vacuum cleaner that could suck up every mosquito that came near your cow, you would have a mosquito trap.
If you used this trap for several weeks, you would start to make a dent in the population of female mosquitoes. After four to six weeks, you could probably create enough of a dent to start to depress the entire mosquito population in your yard. With the number of female mosquitoes down, there would be a lot fewer eggs being laid. That, in turn, would mean fewer mosquitoes, and eventually the population would collapse.
Most neighborhoods do not allow cows, and standing next to the cow to vacuum up the mosquitoes would be labor-intensive, but this trap would work. To make a practical trap, what we need to do is create an artificial cow and an automatic vacuuming system...

Creating a Mosquito Magnet
To create an artificial cow, you need to have three things:
A way to produce carbon dioxide
A way to create warmth and moisture
A way to produce the plant chemicals that cows produce
If you have these three things, you have everything you need to attract many varieties of mosquitoes. A machine that combines an artificial cow with an automatic vacuuming system would make a very effective mosquito trap.
Several manufacturers have created such a machine, and one of them is called the "Mosquito Magnet." The way these machines work is quite ingenious.
The source of the carbon dioxide in the mosquito trap is propane. Propane is a gas that contains carbon and hydrogen, so when you burn it you get carbon dioxide and water vapor. Traditionally, we burn propane with a flame, for example in a barbecue grill.
Modern mosquito traps put an interesting twist on the burning process. Instead of a flame, they "burn" the propane catalytically, using the same idea as that used in the catalytic converter on your car.
The propane comes in and hits the catalyst -- a set of ceramic beads or a ceramic grid coated with platinum. The catalyst converts the propane directly to heat, carbon dioxide and moisture without actually needing a flame. The advantage of this system is that you can catalyze very small quantities of propane over a long period of time without having to worry about the flame ever going out. In addition, there are no worries about other gases, like carbon monoxide or nitrogen oxides, being produced by the flame. The lack of a flame also cuts down on fire risks.

Completing the Mosquito Trap
Carbon dioxide is not enough. To complete the chemical signature you add a cartridge that contains either octenol (a generic molecule that simulates plant chemica­ls) or Lurex (a proprietary mixture that simulates sweat chemicals). These chemicals act as strong attractants for different types of mosquitoes. Lurex-type chemicals work best on imported tiger mosquitoes, while octenol works best on mosquitoes native to the United States.
By mixing the chemical attractant with the carbon dioxide and moisture and then blowing it out into the surrounding air, the trap creates a plume of gas that mosquitoes find irresistible. They will fly upwind to follow the plume to its source.
When the mosquitoes get to the mosquito trap, they encounter a vacuum created by a fan, just like a vacuum cleaner. The fan sucks in air and the mosquitoes. The mosquitoes are trapped in a net bag, where they dehydrate and die.

Do Mosquito Traps Work?
When they are set up properly, put in the right place and tuned to the appropriate species of mosquito (with the correct attractant ­chemical), mosquito traps can be very effective. According to the Mosquito Magnet Web site, the most successful case is that of a U.S. Coast Guard station in the Bahamas. The station had become unusable because of swarms of mosquitoes. Six Mosquito Magnets® captured 1.5 million mosquitoes in six days. Eventually, the population collapsed. Mosquito Magnet: Testing contains a number of cases like this.
When a mosquito trap does not work, often the problem can be traced to either the choice of attractant or the placement of the unit. The trap must be placed upwind from the area where mosquitoes are breeding and living. And the chemical attractant must match the species of mosquitoes living in the area.
Even when used correctly, a mosquito trap takes time. It has to be in place four to six weeks to have a significant effect on the mosquito population. It takes that long for existing eggs to hatch and get captured. Once they have been trapped, the population starts to decline.
For more information on mosquito traps and related topics, check out the links on the following page.

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