Nature’s Nasty Little Pest, the Mosquito

I am one of those people that mosquitoes seek out. If one gets in the house, it will inevitably find me sometime before morning. My wife has only occasionally been bitten. So what is it about me that attracts mosquitoes?
Mosquito means “little fly” in Spanish. This little insect has been honing its skills to find me and bite me for at least 30 million years now. We know this because amber, a petrified tree sap dated to 30 or so million years ago, is sometimes found with insects, including mosquitoes, trapped inside.
Incidentally, the plots of the Jurassic Park books and movies of a few years ago that depended on dinosaur DNA from mosquitoes trapped in amber to recreate dinosaurs, ignored the fact that dinosaurs died out 65 million years ago, well before the amber was formed. That’s why they call it fiction.
Of the many species of mosquitoes in the world, all, including both males and females are plant nectar feeders. Unfortunately, in the several species that we encounter, the female must also feed on blood before she lays egg in order for the eggs to develop. Females live for a few weeks and produce more than one crop of eggs. Males live a much shorter time and don’t bite. If you hear the high pitched whine of a mosquito approaching you can be sure that it is a female. The whine of the females enables males to locate them with specialized antennae.
Mosquitoes are not just pests. In many parts of the world they are responsible for millions of deaths from the diseases that they sometimes carry. The diseases include malaria, yellow fever, dengue, several forms of encephalitis, and West Nile virus. Some of these diseases have made their appearance in the US.
The female mosquito seems as well equipped as a military fighter plane in her search for targets. She has sensors for multiple chemicals including carbon dioxide in exhaled breath and various compounds found on the skin. In addition she has sensitive heat sensors to find warm bodies and vision that is sensitive to contrasting colors and motion. All of this means that she is attracted to all people and many other warm-blooded animals.
So why are some people, like me, more attractive than others? Only recently has this tendency been confirmed. Even more recently some answers have been found. Researchers at Rothamsted Research in the U.K. have made sophisticated studies of people prone to bites and those not.
The researchers collected samples given off by groups of subjects that were either prone or not prone to bites. The daunting task of analyzing the hundreds of compounds given off was made possible with the use of a technique called gas chromatography-electroantennography. The chromatograph separated tiny samples of each component and microscopic electrodes attached to the antenna of a mosquito registered the response to each. Using this procedure they were able to isolate a handful of compounds given off by those not prone to bites that deter the mosquito. The same chemicals were not present in those prone to bites. The research is still ongoing, but apparently those not prone to mosquito bites give off some compounds that repel or somehow confuse the insect. Some of these compounds are being looked at as better and safer repellents than the current gold standard of DEET which is the common component in most insect repellants.
The researchers in the U.K. speculated, but did not prove, that some of the repellant compounds found in those not prone to mosquito bites could be related to stress. Perhaps a more stress prone individual is better protected. Could it be that the mosquito takes pity on those who are stressed out and is out to get me because I am too laid back? Surely not.