Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
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Species Ixodes pacificus - Western Black-legged Tick

Ixodes pacificus female? - Ixodes pacificus - female Unknown Tick - Ixodes pacificus Cat tick - Ixodes pacificus - female Cat tick - Ixodes pacificus - female Cat tick - Ixodes pacificus - female Cat tick - Ixodes pacificus - female Ixodes pacificus Ixodes pacificus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Subclass Acari (Mites and Ticks)
Superorder Parasitiformes
Order Ixodida (Ticks)
Family Ixodidae (Hard Ticks)
Genus Ixodes
Species pacificus (Western Black-legged Tick)
adult body length about 3 mm
Adult and Nymph: legs, head, and thoracic plate black; female abdomen dark reddish; male abdomen blackish; 8 legs; nymph about half as large as adult

Larva: 6 legs, lighter color, and about one-quarter as large as adult
western United States and British Columbia (range does not overlap with Ixodes scapularis, the Deer Tick - see distribution map)
forests, north coastal scrub, high brush, and open grasslands; nymphs are commonly found on moss-covered tree trunks
may be present any time of year
adults feed on blood of large mammals such as deer, dogs, coyotes, horses, and humans
subadult stages feed on blood of lizards and small rodents
The Western Black-legged Tick is a vector of the Lyme Disease Borrelia burgdorferi spirochete, Babesia microti, and the equine granulocytic Ehrlichiosis equi rickettsia
Internet References
various life stage images and other info (Rhode Island Dept. of Health)
adult female image (U. of California at Berkeley)
adult images and comparison with other tick species (Canadian Lyme Disease Foundation, British Columbia)
comparison with other ticks in California (U. of California at Davis)
nymphal habitat; PDF doc (Ted Slowik and Robert Lane, Journal of Vector Ecology)
as a vector of Ehrlichia equi in horses (PubMed, National Institutes of Health)
as a vector of Borrelia burgdorferi (PubMed, National Institutes of Health)
as a vector of organisms that cause Babesiosis, Lyme Disease, and Ehrlichiosis (Rhode Island Dept. of Health)
distribution maps of several tick species (Centers for Disease Control)
distribution in Canada (Public Health Agency of Canada)