Dr. Brian Scholtens, a professor of biology at the College of Charleston, calls them “flying teeth,” and for good reason.

“Only the females bite,” he said. “They need the protein from your blood to feed and raise the next generation of no-see-ums. They literally have mandibles that take a chunk out of your skin and suck your blood.”

http://www.postandcourier.com/news/2010/apr/22/our-endless-battle-with-no-see-ums/