The term "no-see-ums" usually refers to several species of biting midges in the Ceratopogonidae family. Most species are under 1/8-inch long and can be difficult to see with the naked eye. Like mosquitoes, only the females of most species bite, and they use the blood to develop their eggs.
"No-see-ums" can be found throughout North America. They are small enough to get through traditional window screens. The best way to combat these pests is to use fine mesh screens around tents and windows. Insecticides have a limited effect on most species. Their preferred hosts are mostly mammals, but birds, reptiles and amphibians can also be victims.