Western blacklegged ticks are closely related to the eastern blacklegged (deer) tick (Ixodes scapularis). They would be hard to tell apart without the aid of a microscope but the eastern version of this tick has never been reported from the west coast unless there was a recent travel history somewhere east. In most Pacific coastal states, the adult stages typically start to become abundant by early December and remain active all winter into early summer when their activity is curtailed by lowering humidity. The nymphs are most abundant in April, May, and June. Immature stages (larvae, nymphs) readily attach to and feed on lizards and small rodents. The high level of immature tick blood-feeding on lizards is likely a main factor limiting the tick infection rate (usually <5% of ticks are infected) with Borrelia burgdorferi, as lizards are not competent reservoir hosts for this bacteria.