Ticks are not insects, being more closely related to spiders (Arachnids). They have eight legs and an unsegmented body. Eyes are small, even absent. Unlike most biting insects, blood is the regular diet of ticks of both genders, all ages and developmental stages.

The tick anesthesizes surrounding tissue, drives in a barbed tube, and cements its body to the host's skin. The ability to greatly expand the body (sometimes over 200 times) as blood is consumed is restricted to females.

Ticks go through four stages: egg, larval, nymphal and adult. After hatching, each later stage requires just one (sometimes extended) blood meal.

The cycle takes up to three years, and months may pass between meals. Newly hatched nymphs find hosts by climbing vegetation to wait with legs extended until they are brushed off by passing vertebrates. Some species go through their entire cycle on one animal. Others fall off and choose another host after each stage.