Ticks are relatives of spiders, scorpions and mites. As such, their survival is dependent upon a host (i.e., they're parasites). Specifically, ticks feed on an animal's blood or body fluids. The deer tick (ixodes scapularis in the East and Midwest and ixodes pacificus in the West) goes through many stages during its life cycle and feeds on different species at each point.
Ticks begin as eggs (stage one) that hatch into six-legged larvae (stage one).
Larvae live and feed on animals (mice, deer, squirrels, livestock and any humans who enter the tick habitat) for about a week before detaching, then molting (shedding) anywhere from one week to eight months later.
The larvae then become eight-legged nymphs (stage three). Nymphs feed on animals, engorge for three to 11 days, detach and molt about a month later (depending on the species and environmental conditions).
Once the nymph molts, it becomes an adult tick (male or female). Ticks climb up grass and plants and hold their legs up "sensing" and "looking" for their prey. Ticks are attracted to their hosts by detecting carbon dioxide and heat through special organs located on the first pair of the tick's legs (Haller's organs). When a warm-blooded animal walks past, the tick can crawl onto it and begin feeding. Ticks insert their mouths, attach to their prey and engorge themselves with a blood meal (stage four). During feeding, tick saliva can get into the host's body and bloodstream. Any tick infected with Borrelia burgdorferi can then inadvertently spread this bacterium to the host.
Male and female ticks usually mate while attached to the host. A few weeks later, the engorged female detaches from the host and lays her eggs (1,000-8,000 eggs) on a leaf. A tick usually lives a year before dying.
(L to R) larva, nymph, adult male, adult female, engorged female