Tick:

common name for an arachnid that is closely related to the mite. Ticks are parasitic on many animals, including sheep, cattle, deer, dogs, birds, reptiles, and humans. Approximately 850 species occur in the world; most are known as “hard ticks”, the remaining 175 are called “soft ticks”. Hard ticks are often found in woods or among thick vegetation, while soft ticks are typical of buildings and nests. Ticks have a tough, rounded body and eight legs (the larvae have only six). The mouthparts include a toothed anchoring organ, or hypostome, and a pair of large, sharp chelicerae (jaws). On the skin of a host animal, the tick makes a cut to insert the hypostome and sucks the blood for a period of days. The tick also mates while on the host. The female lays her waxy eggs after she leaves the host and the hatched larvae must find their own new hosts on which to feed. The young larvae are tiny (less than 1 mm long) but enlarge greatly when feeding; adult females may increase their weight up to 150 times when fully fed. They moult in order to allow body growth. The world’s largest engorged tick measured 28 mm (1 in). The life cycle of a tick may last three years. Several diseases, such as Lyme Disease and Rickettsia, are transmitted to humans by ticks as they feed.
Scientific classification: Ticks constitute the suborder Ixodida within the class Arachnida (subclass Acarina).