Lyme disease is primarily spread through the bite of a tick. Ticks, which are related to spiders and have eight legs, can be a variety of sizes (as small as 2 millimeters) and are usually black, brown, or red in color (see image). Ticks live in the woods, on leaves and bushes, and on blades of grass. Ticks stay alive by eating blood from their hosts, including humans. As they move from one host to the next, ticks can transmit infections, one of which is Lyme disease.