Larvae and nymph stages also are active spring through fall, but often at different times than the adults. Because of their small size, larval and nymphal ticks often are difficult to detect even when attached. Although some ticks are fairly selective about hosts, many will attach to almost any animal they encounter including mammals, birds, and reptiles. The Western Black-Legged Tick also is known as the Pacific Tick. It is common in western Oregon, and is found in California and southern Washington.
Adults generally feed on large mammals, including humans.
Both adults and immatures may transmit the disease. The tick usually must be attached for 24 to 48 hours before it can pass the bacterium to humans. Both species are closely related to I. pacificus. Fourteen species of ticks belonging to the genus Ixodes are known to reside in Oregon. Only the species, I. pacificus, is commonly found on large mammals, including humans.