Before feeding it is round or oval, and quite flat. After burying its beak and head beneath the skin, and gorging itself, the bloated body may be five or six times as long. It should be removed, as soon as possible, by a straight slow pull with the fingers, without jerking. Otherwise the head may break off and a needle or knife will be required. There may be from 3 to 8 molts, depending upon the species, before they become adult.
Some kinds complete the life cycle in less than a year, while others require up to four years.
Some have simple eyes. Others have no eyes but possess special sense organs that enable them to detect animals many feet away. A camper, or a man standing in the woods, may attract ticks from a large area and find scores of them crawling up his legs. In addition to tick paralysis, Colorado tick fever and relapsing fever, none of which is fatal, ticks are known to be responsible for two diseases which sometimes cause death to humans. Rocky Mountain spotted fever has been known in the Bitterroot Valley of Montana since 1872 but now is found in most of the 48 states.