Ticks, like spiders, are a type of arachnid. These eight-legged creatures hide in leaf litter or low vegetation in forests. They sit with their front legs outstretched, waiting for an animal to brush by. When that happens, the parasite burrows its mouth into the animal’s flesh and begins drinking its blood—ticks’ only source of food. Ticks need just one of these blood meals between each life stage—egg, larva, nymph, and adult (see The Life Cycle of a Tick).
When a tick bites, it may pick up diseases from the host it’s living on. As a larva, for example, a tick might feed on a mouse carrying a disease. When it’s finished feeding, the larva drops to the ground and begins the nymph stage of its development. The nymph goes looking for its next meal. When it bites this time, it transmits the disease it picked up from the mouse to its new host.