http://www.npr.org/sections/health-shots...your-blood
Quote:It's not just idle curiosity that's got scientists hunting down all the bloody details of a mosquito bite. Bites from these bugs are more dangerous to humans than those of any other animal; mosquitoes kill hundreds of thousands of people each year worldwide, and sicken millions more.
Male mosquitoes don't bite people, but when the females drink our blood to grow their eggs, they can leave behind viruses and parasites that cause diseases like West Nile, malaria, dengue and Zika.
Part of what makes mosquitoes so good at getting humans sick, researchers are now learning, is the effectiveness of that bite. The mosquito's mouth, also called a proboscis, isn't just one tiny spear. It's a sophisticated system of six thin, needlelike mouthparts that scientists call stylets, each of which pierces the skin, finds blood vessels and makes it easy for mosquitoes to suck blood.
And these bugs know just where to bite. Mosquitoes have more than 150 receptors — proteins on their antennae and proboscis that help them find victims or figure out if a particular puddle of water has enough nutrients to support mosquito larvae.
Unfortunately, we humans leave an alluring trail. When malaria-causing Anopheles mosquitoes, for example, come out at night to look for blood, they track the carbon dioxide we exhale as we sleep, explains Shirley Luckhart, a University of California, Davis, parasitologist and entomologist. As they get closer to us, they detect body heat and substances called volatile fatty acids that waft up from our skin, she says.
Why are some people more likely to get bitten than others? Nobody knows for sure.
"The volatile fatty acids given off by our skin are quite different [from one person to the next]," Luckhart explains. "They reflect differences between men and women, even what we've eaten. Those cues are different from person to person. There's probably not one or two. It's the blend that's more or less attractive," she says.
When the female mosquito pierces the skin, a flexible liplike sheath scrolls up and stays outside as the insect pushes in the six needlelike parts.
Two of these needles, called maxillae, have tiny teeth that let the mosquito saw through human skin. ...