HOW COME? Why you may be a mosquito magnet

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Why are some people apparently more prone to mosquito bites than others? My Dad seems to be a favorite meal whenever we go out, but the rest of us are unscathed. -- Joanne Schmidt, of HuntingtonNo matter how many bites we may get at an evening barbecue, we're not really dinner. Mosquitoes get the calories they need to live by sipping sugary plant nectar and fruit juices. But after their high-carb meals, the females in most species buzz out for a bit of protein-rich blood. The after-dinner drink isn't optional, since the amino acids in animal blood are required for egg development.

Some mosquitoes get the blood they need from birds, lizards, and other animals. But many species prefer people.

Human blood is especially rich in threonine, important in the production of mosquito egg proteins. A mosquito looks around to see what's moving, sniffs the air (with her antennae) for our exhaled carbon dioxide, and makes a beeline for warm bodies.

But among your family and friends, who will get bitten? Scientists say that a large part of a mosquito's brain is dedicated to the sense of smell, making her exquisitely sensitive to odor molecules.

Proteins in a mosquito's antennae capture odors emitted from skin, allowing mosquitoes to choose from a menu of scents. In one experiment, volunteers rubbed Petri dishes on their skin. When the dishes were put in an enclosure with the insects, mosquitoes alighted repeatedly on a favored few.

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Scientists have found that malaria-transmitting mosquitoes prefer human targets with abundant skin bacteria, but with fewer varieties. The more diverse the bacteria colony, they say, the more likely that some bacteria are making chemicals that interfere with the scents that attract mosquitoes.

Mosquitoes also seem to land on more men than women, probably because they tend to be larger, generating more heat and carbon dioxide. But pregnant women, who also produce more heat and CO2, are mosquito magnets.

Studies of identical twins show that whether a mosquito likes you is largely genetic: Twins lured about the same number, presumably because they smelled equally attractive. Meanwhile, most human beings release odor markers of their blood type, which mosquitoes detect. One study found that people with Type O blood were more likely to be landed on.

Finally, researchers found that beer-drinking (versus water-sipping) volunteers attracted many more of the thousands of mosquitoes let loose in the experiment.

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