(Lansing State Journal, June 11, 1997)
Actually, only the female mosquitoes bite people. They are searching for isoleucine. Isoleucine is one of the basic building blocks of life called an amino acid. Amino acids are what make up proteins, and female mosquitoes need these proteins to make eggs. If they find isoleucine then they may lay as many as 100 eggs. But if they do not find isoleucine then they may only lay at most ten eggs.
So how do the mosquitoes find isoleucine? Isoleucine is part of our blood. The female mosquito punctures our skin with a part of her mouth known as her feeding stylets. Then she searches for blood vessels within our skin. A female mosquito usually finds a blood vessel in less than a minute. Next she sucks our blood through one mouthpiece. She can swallow up to four times her weight in blood, and when she is full she looks like a tiny red light bulb. She can do this because while she is sucking our blood, she is also injecting us with her saliva. There are special chemicals in her saliva which keep our blood from clotting.
Actually, human blood is not the best source for isoleucine. Blood from buffaloes and rats contains more isoleucine, but since people outnumber rats and buffaloes in many places the mosquitoes bite us instead.