These are ectoparasites. The general life cycle of Dermacentor spp. involves adult males and females, eggs, larvae and nymphs. Larvae must take a blood meal before molting to become a nymph; the nymph must take a blood meal before molting to the adult stage, and adult females must take a blood meal before they can produce eggs.
Some species are one-host ticks, others are three-host ticks, depending upon whether they remain on the host and molt after each blood meal, or drop off and molt on the ground, then re-attach to a new host. Ticks in other genera may also be two-host ticks, with larvae and nymphs on one host, and adults on a second host.
In all species the female drops off the host to deposit eggs on the ground. The larvae which hatch from the eggs often ascend vegetation and are stimulated to attach to passing hosts by the presence of carbon dioxide. Life cycles are typically completed in one year.