This species takes two years to complete its life cycle and distribution relies heavily on the white-tailed deer, which serve as the reproductive host. The larvae of the deer tick are active July through September, hatch from eggs into leaf litter and remain there until attaching to any available mammal, as well as birds. Larvae have six legs and are about the size of a poppy seed. After feeding, the larvae drop off the host, molt, and emerge as nymphs in the spring. Nymphs are active May through August, have eight legs and are about the size of a pinhead. This life stage of the deer tick will attach to smaller mammals but will also feed on humans, cats and dogs before dropping off, molting, and emerging as adult deer ticks in the fall. Adults are active October through May and prefer larger hosts, including humans and pets. Adult males do not feed and are uniformly brown in color and slightly smaller than adult females. The adult female feeds, drops off into leaf litter to overwinter, then lays a single egg mass before dying. An unfed female deer tick is 3 to 5 millimeters long and red and brown colored with eight legs. An engorged female appears darker and can reach 10 millimeters in length.
This tick species transmits Lyme Disease, Anaplasmosis and Ehrlichiosis.
Of the many different tick species found throughout the world, only a select few bite and transmit disease to humans. These maps provide general insight into the expected distribution these human-biting ticks in the contiguous United States. Populations of ticks may be found outside noted areas. Naturally occurring populations of the ticks described below do not occur in Alaska; however, the brown dog tick is endemic in Hawaii.
Note that adult ticks are the easiest to identify and male and female ticks of the same species may look different. Nymphal and larval ticks are very small and may be difficult to identify.