Mosquito feeding habits
Female mosquitoes bite because they need protein found in blood to develop their eggs.
They choose their targets through a combination of smell, heat and visual cues, and continue seeking bloodmeals until their abdomens are full. The females can live up to about a month and feed every two or three nights during that time.
The most common mosquito species feed at dawn and dusk, and for a few hours into dark. However, there are some species that are particularly aggressive and will feed both day and night.
Mosquitoes locate bloodmeals first by using sensors on their antennae to detect trace amounts of carbon dioxide released in human breath. That CO2 rises in plumes that mosquitoes can sense from hundreds of feet away.
A mosquito seeking prey follows the plume toward its source. Once it's close enough, it begins to pick up other chemical odors that signal the presence of people. Human skin produces more than 340 of these chemical signatures, including octenol, a substance also found in the exhalation of cows.
Certain people will smell better to the mosquito than others, and scientists are not exactly sure why. Larger people and pregnant women tend to attract mosquitoes, possibly because they release more CO2. Cholesterol and folic acid also act as attractants, as do perfumes, colognes, and lotions.
The mosquito also depends on its large compound eyes, designed for spotting motion, to help guide it in. Two simple eyes, called ocelli, are photosensitive, so the mosquito keys on lights and bright colors as well.
Finally, thermal sensors on the insect's antennae and around its mouth detect heat emanating from warm-blooded bodies, allowing it to land on exposed skin and find capillaries closest to the surface.
Then, the mosquito pierces the skin with a serrated proboscis containing two tubes. Through one, it injects saliva that numbs the area and keeps the blood from clotting. Through the other, it begins to suck blood into its abdomen.
The mosquito will drink until it is full, withdraw the proboscis and fly away. Often, the person bitten doesn't even realize it until a minor allergic reaction causes the site to swell and itch.