Two-host ixodid tick life cycle

Two-host ixodid ticks have a life cycle that usually spans over two years. Gravid females drop off the second host after feeding to lay eggs (1), usually in the fall. Eggs hatch into six-legged larvae (2) and overwinter in this stage. The following spring, the larvae seek out and attach to the first host (3), usually a rodent or lagomorph. The larvae molt into nymphs on the first host (3a-3b). Engorged nymphs drop off the first host, usually in the late summer or fall (4) and overwinter in the nymphal stage. Nymphs molt into adults the following spring (5) and seek out the second host (6), which is usually a larger herbivore (bovids, cervids, etc). Adults feed on the second host during the summer and mate. In the fall, females drop off the second host to continue the cycle. Females may reattach and feed multiple times. Humans may serve as first or second hosts for ticks with this life cycle. Also, the second host does not necessarily have to be a separate species or even a separate individual as the first host.