Which developmental stage of *Ixodes pacificus* is most frequently responsible for biting humans?

Nymph

The nymphal stage of the Western Blacklegged Tick is identified as the stage most frequently responsible for biting humans, leading to the majority of tick-borne illness transmissions to people. This elevated risk is primarily attributed to two factors: size and activity timing. Nymphs are quite small, allowing them to attach to a host discreetly, often going unnoticed while they are actively feeding and engorging. Furthermore, nymphs are active during warmer months when human outdoor activity increases, presenting a significant exposure risk. Because the host is often unaware of the feeding activity until much later, the window for pathogen transmission from an infected nymph is considerably widened, making this stage epidemiologically significant.