Tick Lifecycles: Four Stages, a Blood Meal at Each, and Where Disease Comes In

Blacklegged ticks at each life stage, on a dime. Image from CDC's page on tick lifecycles

The basics

• Four stages: egg, larva (six legs), nymph (eight legs) and adult.
• Blood at every stage: once hatched, a tick must feed on blood at each stage to survive.
• Disease timing: ticks usually pick up pathogens young — as larvae or nymphs feeding on animals — and pass them on later, as nymphs or adults, to other animals or to people.

Hosts

Ticks feed on mammals, birds, reptiles and amphibians. Most species want a different host at each stage. Those that need that many hosts can take up to 3 years to finish their life cycle, and most die because they never find their next host. A few, like the brown dog tick, prefer to stay on the same host throughout.

Three species compared

Blacklegged tick: a two-year cycle

Eggs are laid in spring and hatch into larvae in summer. The next spring, nymphs feed, then molt into adults in the fall. Adult females look for a blood meal and lay eggs the following spring.

Blacklegged tick (Ixodes scapularis) life cycle. Image from CDC's page on tick lifecycles

Western blacklegged tick: a three-year cycle

Eggs laid in spring hatch into larvae the following spring. Larvae feed in summer and molt into nymphs the next spring; nymphs feed that summer and molt into adults over the winter. Adult females seek a winter or spring blood meal, then lay eggs in spring.

Western blacklegged tick (Ixodes pacificus) life cycle. Image from CDC's page on tick lifecycles

Brown dog tick

Typical life cycle of the brown dog tick (Rhipicephalus sanguineus). Image from CDC's page on tick lifecycles

Sources

Based on "Tick Lifecycles," Centers for Disease Control and Prevention; a work of the United States government in the public domain.