Tick basics awaiting entomology signoff
Blacklegged tick / deer tick
Ixodes scapularis
Look for a smaller tick with a plain dark shield and a reddish-brown adult female body, not a white patterned shield.
I
approx. 3-5 mm unfed
Size by life stage
- Adult female
- approx. 3-5 mm unfed source caveated editorial
- Adult male
- approx. 2-3 mm unfed source caveated editorial
- Nymph
- approx. 1-2 mm ("poppy-seed sized") source caveated editorial
- Larva
- approx. 0.5-1 mm; larvae have 6 legs source caveated editorial
How to tell it apart
- Scutum: Plain dark brown to black scutum; no ornate white markings.
- Color (unfed): Adult female often reddish-orange to brown behind the dark scutum; legs appear dark.
- Color (engorged): Body can swell and shift gray, tan, or blue-gray; engorgement makes species ID less reliable.
Where it lives
Region: Established across much of the eastern and upper-midwestern U.S.; range varies by local surveillance source.
Habitat preference: Humid wooded areas, leaf litter, brushy edges, and ecotones with deer/rodent hosts.
Hosts: humans, dogs, deer, rodents, birds, wildlife
Where this species shows up in our state guides
Primary species in: California, Connecticut, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Tennessee, Vermont, Virginia, Washington, Wisconsin
Secondary or emerging in: Arkansas, Florida, Georgia, North Carolina, Texas
Disease associations
- can transmit Lyme disease
- associated with anaplasmosis
- associated with babesiosis
- associated with Powassan virus disease in some regions
Look-alikes
- western blacklegged tick
- american dog tick
- lone star tick
- small scabs or freckles in poor photos
Sources
- CDC Where Ticks Live
- CDC Tick Life Cycles
- PA DEP Blacklegged Tick
- PA Tick Research Lab Tick Identification