Black-legged deer tick Ixodes (dammini) scapularis.

Ixodes scapularis has been reported from at least 125 different species of hosts.
The adults appear to prefer medium to larger sized mammals, the white-tailed deer (Odocoileus virginianus) is the most commonly infested mammalian species.

Like all ticks in the genus Ixodes, I. scapularis is a three host tick. Each feeding stage (larva, nymph and adult) requires one vertebrate blood meal for its development. The life cycle of I. scapularis may range from two to four years and appears to be regulated by host abundance and physiological mechanisms of the tick. The nymphal stage is most responsible for disease transmission to humans.

Four diseases are spread by the bite of I. scapularis, the deer tick: Lyme disease, caused by Borrelia burgdorferii (a type of bacterium); human babesiosis, caused by a protozoan, Babesia microti; human granulocytic ehrlichiosis (HGE) (a bacterial infection); and tick-borne encephalitis

PDF (132 kb): The veterinary Clinics of North America, p. 65-73.