Tick is the common name for the small arachnids that, along with mites, constitute the order 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. The major families of tick include the Ixodidae or hard ticks, which have thick outer shells made of chitin, and Argasidae or soft ticks, which have a membraneous outer surface. A third family, Nuttalliellidae, contains one rare African species, Nuttalliella namaqua. Soft ticks typically live in crevices and emerge briefly to feed, while hard ticks will attach themselves to the skin of a host for long periods of time. Tick bites look like mosquito bites, but can also sometimes bruise or resemble a bullseye. From Wikipedia