The tiny red bugs commonly seen on concrete are known as "clover mites." Barely visible to the naked eye, these oval-shaped arachnids measure just 0.75 to 0.85 millimeters long and have an elongated first pair of legs.
The mites tend to live in large colonies and feed on flowers, grasses, plants and vegetables. While they do not pose a threat to humans, they often become a nuisance to homeowners when they attempt to gain access by hanging around windows and doors, leaving red-colored stains on carpeting and doors when crushed. They may be controlled by applying an insecticide within 15 feet of the structure.