Blacklegged Tick (Deer Tick): ID, Range and Diseases

Quick answer

The blacklegged tick (Ixodes scapularis), also called the deer tick, is a small, dark-legged tick found across the eastern U.S. Nymphs are about the size of a poppy seed and adult females have a red-orange body around a dark shield. CDC lists it as the tick that spreads Lyme disease in the Northeast, mid-Atlantic and north-central states.

What the guidelines say

CDC says Lyme disease is spread in the eastern U.S. by the blacklegged tick, and that young ticks called nymphs pose a particularly high risk because they are common and hard to see. In most cases a tick must be attached for more than 24 hours to pass on the Lyme bacteria, so finding and removing ticks quickly greatly lowers the chance of infection.

What it looks like

Like all hard ticks, the blacklegged tick has four life stages: egg, larva, nymph and adult. Only the last three bite. Ohio State University Extension and the University of Maine Tick Lab describe them like this:

Larva: under 1 mm, with six legs instead of eight.
Nymph: about 1.5 mm, roughly the size of a poppy seed. The body looks see-through to slightly gray or brown, with a small dark shield behind the head.
Adult female: about 2 to 3 mm unfed (sesame-seed size). A red-orange body surrounds a dark brown shield. After feeding she swells many times over and can look gray, tan or dark brown.
Adult male: slightly smaller, dark brown all over, with a shield that covers the whole back and no red color.

All adults have dark brown to black legs, which is where the name “blacklegged” comes from. There are no white or cream markings on the back.

Deer tick vs dog tick

The tick people most often confuse with the deer tick is the American dog tick. A few clues help:

	Blacklegged (deer) tick	American dog tick
Adult size (unfed)	Under 1/8 inch	About 1/4 inch
Back	Plain dark shield; female body red-orange	Reddish-brown with white or cream markings
Adults most active	Spring and fall (even mild winter days)	About April to August
Spreads Lyme disease?	Yes	No (per CDC)

If you are not sure, save the tick in a sealed bag or take a clear photo. Our tick testing guide explains identification options.

Where it lives in the U.S.

CDC describes the blacklegged tick as widespread across the eastern United States. The University of Maine places its range from Maine to Florida and west around the Great Lakes. Lyme disease risk is highest in the Northeast, mid-Atlantic and upper Midwest.

It favors forests with deep leaf litter, woodland edges, tall grass and shrubs, and shaded parts of lawns. It waits on low plants, from ground level up to about 3 feet, and grabs on as you brush past. It does not jump, fly or drop from trees.

A growing range. A 2018 review in the International Journal of Environmental Research and Public Health describes how this tick spread through much of the eastern U.S. and into southern Canada, linked to regrowing forests, more white-tailed deer and milder winters. Ohio is one example: its first established population was found in 2010, and by 2024 Ohio State reported it established in 61 counties, based on 2023 state data. See where ticks live for more.

When it is active

At least one life stage can be out in almost any month when it is warm enough. In general:

Nymphs: late spring and summer, peaking around June. This is the stage most linked to Lyme disease.
Adults: fall and spring. CDC notes adults may look for a host any winter day that is above freezing.
Larvae: summer into fall.

Diseases it can spread

CDC links this tick to more infections than most other U.S. ticks:

Lyme disease (Borrelia burgdorferi and, rarely, B. mayonii)
Anaplasmosis
Babesiosis
Hard tick relapsing fever (Borrelia miyamotoi disease)
Ehrlichiosis (Ehrlichia muris eauclairensis)
Powassan virus disease

CDC also notes a few U.S. cases of alpha-gal syndrome after blacklegged tick bites, though the lone star tick is the species most linked to it. Read more on our co-infections hub.

If a blacklegged tick bites you

Remove it as soon as you can with fine-tipped tweezers, pulling straight up. Our tick bite guide covers removal step by step, and the first 72 hours after a tick bite explains when a clinician may consider a preventive antibiotic and what to watch for over the next month.

When to call a doctor

See a healthcare provider if you get an expanding rash, fever, chills, aches or fatigue in the weeks after a tick bite. Tell them about the bite and where it happened. Learn the early signs on our Lyme disease symptoms page.

Prevention

Because nymphs are so small, preventing bites matters more than trying to spot ticks on the trail. Repellent, smart clothing and a full-body tick check after time outdoors all help. Our practical guides walk through each one:

Prevention is step one of our plan to beat Lyme together.

What patients tell us

We are collecting real experiences about finding and identifying deer ticks from people who have lived it, shared with their permission. As stories come in, they will appear here, clearly marked as personal experience rather than medical advice.

Share your experience

At a glance

Scientific name	Ixodes scapularis
Other name	Deer tick
Size	Nymph about 1.5 mm; unfed adult 2 to 3 mm
Key marks	Dark legs; female red-orange body with dark shield
Range	Eastern U.S., highest Lyme risk in Northeast, mid-Atlantic, upper Midwest
Peak bite risk	Spring, summer and fall
Spreads Lyme?	Yes

Compare it with other species in our types of ticks guide, or see the full list of ticks that carry Lyme disease, including its Pacific cousin, the western blacklegged tick.

Frequently asked questions

Is a deer tick the same as a blacklegged tick?

Yes. “Deer tick” is the common name for the blacklegged tick, Ixodes scapularis. Adults prefer to feed on deer, which helps explain the nickname.

How can I tell a deer tick from a dog tick?

Deer ticks are smaller (adults under 1/8 inch), have dark legs and a plain dark shield, and adult females have a red-orange body. American dog ticks are about 1/4 inch with white or cream markings on the back.

Do all deer ticks carry Lyme disease?

No. Only some ticks are infected, and rates vary by place and life stage. A tick usually needs to be attached more than 24 hours to pass on the Lyme bacteria, according to CDC.

Are deer ticks active in winter?

Adults can be. CDC notes adult blacklegged ticks may look for a host whenever winter temperatures are above freezing, so checks still matter on mild winter days.

Blacklegged Tick (Deer Tick): How to Spot It and What It Spreads