Tick is the common name for the small arachnids in superfamily Ixodoidea that, along with other mites, constitute the Acarina. Ticks are ectoparasites (external parasites), living by hematophagy on the blood of mammals, birds, and occasionally reptiles and amphibians. Ticks are important vectors of a number of diseases, including Lyme disease and Tick-borne meningoencephalitis. According to Pliny the Elder, ticks are "the foulest and nastiest creatures that be."

Young ticks have six legs, and more mature ticks have 8 legs. They are about the size of a sesame seed, and males are black; females are brick-red abdomen with a black shield-like plate close to their head.

Habitats and behaviors

Ticks are blood-feeding parasites that are often found in tall grass and shrubs where they will wait to attach to a passing host. Physical contact is the only method of transportation for ticks. Ticks do not jump or fly, although they may drop from their perch and fall onto a host. Some species actively stalk the host by foot.

Changes in temperature and day length are some of the factors signaling a tick to seek a host. Ticks can detect heat emitted or carbon dioxide respired from a nearby host. They will generally drop off the animal when full, but this may take several days. In some cases, ticks will live for some time on the blood of an animal. Ticks have a harpoon-like structure in their mouth area, known as a hypostome, that allows them to anchor themselves firmly in place while feeding. The hypostome has a series of barbs angled back, which is why they are so difficult to remove once they have penetrated a host. When removing it, it is more likely to rip the tick in half than pull it free.

Ticks can be found in most wooded or forested areas throughout the world. They are especially common in areas where there are deer trails or horse paths.

Some of the more common diseases that can be contracted from a tick bite include (listed alphabetically): Babesiosis, Ehrlichiosis, Lyme disease, Rocky Mountain spotted fever, Southern tick-associated rash illness, Tick-borne relapsing fever, and Tularemia

Case Study of the American Deer Tick

The blacklegged or deer tick (Ixodes scapularis) is dependent on the white-tailed deer for successful reproduction. Larval and nymph stages (immature ticks that cannot reproduce) of the deer tick feed on birds and small mammals. The adult female tick needs a large 3 day blood meal from the deer before she can reproduce and lay her 2000 or more eggs. Deer are the primary host for the adult deer tick and are key to the reproductive success of the tick.Stafford K.C. 2004. Tick management handbook: an integrated guide for homeowners, pest control operators, and public health officials for the prevention of tick-associated disease. The Connecticut Agricultural Experiment Station, New Haven, Connecticut, USAFact: date=June 2008 See the Connecticut Agricultural Experiment Station and Connecticut Department of Public Health joint publication "Tick Management Handbook" for more details of the tick's life cycle and dependence on deer.