2018-07-25 / Front Page

‘Mosquito Bait’

I like to go for leisurely walks with my wife. It is romantic and we get to exercise and enjoy nature together. I like it when we are able to use this time to talk. She says communication in a marriage is important. I agree.

During spring and summer – when mosquitoes are out — I especially enjoy her company. Why? The answer is quite simple ... BAIT.

The way I see it, a mosquito bites only one person. And I don’t want it to be me. So, to protect myself, I looked into what attracts mosquitoes. This is what I have come up with.

Movement is attractive to mosquitoes. I suspect that they associate movement with a live animal — and mosquitoes definitely are attracted to live bodies, because that is where the blood is.

Carbon dioxide (CO2) is also an attraction. Mosquitoes key in on it and move toward it. CO2 is produced when people perspire, and presumably, the more CO2 that is released, the greater the attraction. People tend to perspire and thus produce more CO2 when talking – less when listening.


Recently satiated mosquito. (Courtesy Photo by John Obermeyer) Recently satiated mosquito. (Courtesy Photo by John Obermeyer) I try my best to really listen while my wife talks because this brings us closer together.

But other things attract mosquitoes. Color, for example. It has been proven that dark colors are more attractive to mosquitoes than are lighter colors. I found some recent, cutting-edge mosquito attraction research to be very instructive. In the study, a large, airtight, Plexiglas container was constructed; plate size colored circles of paper or cloth were positioned inside. Video cameras documented the feeding behavior. When the chamber was filled with hundreds of hungry mosquitoes, they just flew around randomly until a puff of CO2 was introduced. Then, it was like magic – all of the mosquitoes instantly descended upon the dark colored circles and attempted to bite. The dark colors were almost like a magnet. It was very impressive.


Recently deceased mosquito. (Courtesy Photo by John Obermeyer) Recently deceased mosquito. (Courtesy Photo by John Obermeyer) The researchers concluded that dark colors, in the presence of CO2, triggered an immediate feeding response by mosquitoes. They sought out the dark objects and attempted to bite. The take-home message for me was that if two people are moving together, CO2 is in the air, and if one person is wearing dark colors and the other light, the dark-clothed person loses.

Incidentally, I am always sure to mention to my wife how good she looks in her darker workout clothes. She smiles and then sometimes holds my hand. Me? I always wear white. No matter what — always a white T-shirt.

I am often asked if it is true that mosquitoes are selective in who they bite, and if so, how do they discriminate. It is a fact that mosquitoes are preferentially attracted to certain people. Some of you probably know what I am talking about. You may even be one of those people who naturally attract mosquitoes.

The complete answer as to whether mosquitoes discriminate or not, however, is not simple. It includes a few things we know and many things that we wish we knew.

It is always best to start with what we know. There are about 75 different species of mosquitoes in the U.S. Each has its own biology, life history and behavior, so making generalizations covering all mosquitoes is risky. Given this caveat, we do know some general facts. First, bites from mosquitoes are the end result of the female mosquito searching for a blood meal to help her develop eggs. Her search for a potential blood meal begins long before landing on your skin. We have already established that mosquitoes cue into movement and traces of exhaled carbon dioxide. As a hungry mosquito flies toward ever higher CO2 concentration gradients, which means it is getting closer to the actual source, it also begins searching for heat in the same way. I imagine that the closer it gets to a warm, breathing body, the more excited it becomes. If it happens to locate a whole party going on, I can imagine the that the mosquito is nearly giddy with excitement. It then begins selecting a potential victim. But how does it choose?

It does seem that this is more than just a random choice, and research has confirmed that. Everyone has a different skin chemistry, and we know that mosquitoes have a preference. Human skin is replete with a very elaborate array of smells detectable to mosquitoes. Lactic acid, estrogen and steroids, among many other substances, occur naturally on a person’s skin in body secretions, oils, and sweat. These odors are part of our physiology. Some are determined genetically. Some vary from person to person and from day to day. Lactic acid on the skin, for example, increases when a body is perspiring. Some studies show that certain mosquitoes key in on lactic acid. Bacteria on a person’s skin are also responsible for a lot of smells. (I know this from living with teenagers.) I think the answer is yes, mosquitoes are attracted more strongly to certain people, but what is unclear is which substances on a person’s skin are preferred, and at what concentration levels.

When my wife complains that she seems to be bothered by mosquitoes more than I am, I tell her that she must be sweeter. I think that makes her feel better.

Some people have gone a step further by suggesting that altering how they smell might confuse a mosquito. To that end they have tried applying perfumes, lotions, or changed their diet by consuming things such as garlic or lemons, vitamin B–12 tablets, bananas or even beer. Unfortunately, none of these, even in large quantities, have been proven to be effective – although I have some friends who continue to volunteer for the beer study, convinced that the sample size or the number of replications must not be large enough.

So, is there anything a person can do to help prevent mosquito bites? Yes, there are some effective tips. First, simply avoid being out in the places (near shaded vegetation) and times (dawn and dusk) that mosquitoes are most active. This can be predicted but most often learned by experience. Furthermore, when you must be out during those times, wearing light-colored, long-sleeved clothing and apply proven insect repellents. Doing these things, rather than worrying about why mosquitoes don’t bite your friends more, might result in less itching all around.

Most effective mosquito repellents contain DEET as their active ingredient, and are available as sprays, lotions, liquids or even in materials such as cloth or plastic wristbands. Concentrations of DEET vary by product but generally speaking the higher the concentration the more long lasting the effect — at least up to 50%. Beyond that concentration, no improved protection will be realized.

As for my strategy, I try to avoid excessive work and any exertion that might result in increased movement and respiration. I also like to hang out near mosquito bait. Remember the advice about not worrying about outrunning a bear, just worry about outrunning anyone else fleeing the bear? The same general strategy can be used for mosquitoes. I make myself less attractive than the next guy. That way, if there are only a few mosquitoes around, I should be OK.

Now, getting back to my taking walks with my wife and using her as bait ... just so that you do not think that I am entirely heartless, know that I did tell my wife about the mosquito behavior things that I learned. I confessed all of this to her. She knows my strategy. In fact, I even had her approve this column. She still likes me. We still go for walks.

I’ll confess, however, that I have NOT shared this information with my son-in-law. Not yet. In fact, I recently purchased a T-shirt for him. It was a Christmas gift. I told him it is for outdoor exercising.

It is black, with white lettering that says something like “best son–in–law in the world.” I plan to invite him to come along on walks with my wife and me when he visits. I’ll ask questions to ensure that he does most of the talking. The walks will be less romantic with him there, but that’s OK. He’s bait.

I will smile.

I think my wife will smile.

Life is good!

(by Tim Gibb, Professor of Entomology Purdue University)

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