Stage 1 · Before & after a bite

Which tick is this, and does it matter?

Know which tick you’re dealing with.

Read First

Identification narrows the possibilities. It does not diagnose you. A tick carrying a pathogen has not necessarily transmitted it, and an unremarkable tick does not rule out a bite you never noticed. Use this to inform the conversation with your provider, not to replace it — and never delay care for a species you cannot name.
The answer

It matters, because CDC lists different illnesses for different species. For the blacklegged (deer) tick, CDC lists anaplasmosis, babesiosis, Lyme disease, hard tick relapsing fever, ehrlichiosis and Powassan virus disease; for the lone star tick, Bourbon virus, ehrlichiosis, Heartland virus and tularemia; for the American dog tick, tularemia and Rocky Mountain spotted fever. Size and markings tell them apart, and the tick you saved is easier to identify than the one you flushed. Identification is an observation about the tick. It says nothing about whether anything was passed on.Source: CDC, Where Ticks Live, read 10 October 2026.

The one graphicThree ticks, and what CDC lists each one as transmitting

What a tick carries is not just Lyme

Three of the ticks that bite people in the United States, and what CDC lists each one as transmitting.

Tick species and the illnesses CDC lists each one as transmittingThree tick species, each with the illnesses CDC lists it as transmitting. The blacklegged tick: anaplasmosis, babesiosis, Lyme disease, hard tick relapsing fever, ehrlichiosis and Powassan virus disease. The lone star tick: Bourbon virus, ehrlichiosis, Heartland virus and tularemia. The American dog tick: tularemia and Rocky Mountain spotted fever. Ehrlichiosis and tularemia are outlined, because CDC lists each of them for two of these species.Blacklegged tickAnaplasmosisBabesiosisLyme diseaseHard tickrelapsing feverEhrlichiosisPowassanvirus diseaseLone star tickBourbon virusEhrlichiosisHeartland virusTularemiaAmerican dog tickTularemiaRocky Mountainspotted feverOutlined: CDC lists it for morethan one of these species.

What CDC lists each species as transmitting — not what any one tick is carrying, and not a diagnosis.

US Centers for Disease Control and Prevention, Where Ticks Live, read 10 October 2026: what CDC lists each species as transmitting. Nothing on this drawing is a measured quantity.

The species cards below quote CDC’s full entry for each of the nine ticks.
The detail

Quick visual key

Start here if you have the tick in front of you. Pick the closest match, then read the full entry — several species are near-identical and separated mainly by where you are.

Size is the detail people get wrong. On the blacklegged tick, CDC says: “Nymphal ticks pose a particularly high risk due to their abundance and small size (about the size of a poppy seed), which makes them difficult to see.”Source: CDC, How Lyme Disease Spreads, read 12 October 2026.

Size, by life stage

Three life stages, drawn to one scale.

The three tick life stages drawn at their true relative sizeThree life stages of the same tick, larva, nymph and adult, drawn to one scale so they can be compared. The larva is the smallest and is drawn with six legs; the nymph and the adult are drawn with eight. A poppy seed is drawn beside the nymph and a sesame seed beside the adult, at the same scale as the ticks.DRAWN TO RELATIVE SCALELarvapoppy seedNymphsesame seedAdult

CDC: “In general, adult ticks are approximately the size of a sesame seed and nymphal ticks are approximately the size of a poppy seed.”

The seeds beside the nymph and the adult are drawn at the same scale as the ticks.

Silhouettes for scale only — not an identification aid. Size varies by species and sex, and a tick that has already fed is larger than any of these.

Life stages and seed sizes: US Centers for Disease Control and Prevention, How Lyme Disease Spreads, read 12 October 2026. The three silhouettes and the two seeds are drawn to one scale; no absolute measurement is shown.

The nine species

The order is not a ranking — which of these matters to you depends mostly on where you are. Each entry covers what distinguishes it, where it lives, when it is active, and what it carries.

  • Blacklegged Tick

    Ixodes scapularis · "Deer Tick" · Ixodidae · Hard Tick

    Called the deer tick across much of the eastern US. Black legs on a reddish-brown body, a teardrop shape and no markings. The nymph stage is barely visible.

    Size
    Adult unfed: about a sesame seed. Nymph: about a poppy seed. Engorged, several times larger again. The life-stage drawing above shows all three to scale.
    Color
    Reddish-brown body with black legs — the "black" in blacklegged. Orange-red scutum (dorsal shield) visible on females.
    Key Feature
    Black legs are the defining identifier. Longer, thin mouthparts. Teardrop-shaped body. No ornate markings.

    What CDC says it can carry

    “Anaplasma phagocytophilum (anaplasmosis), Babesia microti (babesiosis), Borrelia burgdorferi and B. mayonii (which cause Lyme disease), B. miyamotoi (hard tick relapsing fever), Ehrlichia muris eauclairensis (ehrlichiosis), and Powassan virus (Powassan virus disease).”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Geographic Range
    Eastern US (Maine to Florida), Upper Midwest (Wisconsin, Minnesota). Expanding westward. Highest density: Northeast and Mid-Atlantic.
    Peak Activity
    Active any time above freezing.
    Preferred Habitat
    Dense forest, leaf litter, tall grass at forest edges. Requires high humidity. Found in backyards adjacent to wooded areas.
    Found this tick on you? Start the tick-bite walkthrough

  • Lone Star Tick

    Amblyomma americanum · Ixodidae · Hard Tick

    The most visually distinctive tick in North America — the female's single white dot makes it unmistakable. An aggressive tick that actively hunts hosts by sensing CO₂ and movement. All life stages bite humans. Its range has been growing northward.

    Key Feature
    Female has one bright white dot on her back — the "lone star." Males have scattered white markings on body margins. Round, circular body shape.
    Color & Shape
    Reddish-brown to tan. Very round, almost circular body. Long thin mouthparts. Medium-sized — larger than blacklegged, smaller than dog tick.
    Behavior
    Aggressive hunter — actively runs toward hosts rather than waiting (questing). ALL life stages (larva, nymph, adult) bite humans. Can bite in large numbers.
    Size
    Adult female: 3–4mm unfed. Very round — almost looks circular from above. Larva: 0.5mm (nearly invisible).

    What CDC says it can carry

    “Bourbon virus, Ehrlichia chaffeensis and Ehrlichia ewingii (which cause human ehrlichiosis), Heartland virus, and tularemia. A circular rash of unknown cause (STARI) sometimes follows the bite of the lone star tick, and growing evidence suggests that alpha-gal syndrome (red meat allergy) may be triggered by the bite of lone star ticks.”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Geographic Range
    Widely distributed in the Northeast, South and Midwest (CDC). Its range has been growing; why is still being studied — climate, land use and deer numbers are all proposed, and none is settled.
    Peak Activity
    Year-round in far south. Most active when temperatures exceed 70°F.
    Found this tick on you? Start the tick-bite walkthrough

  • American Dog Tick

    Dermacentor variabilis · Ixodidae · Hard Tick · "Wood Tick"

    The largest common tick in the eastern US. Unmistakable ornate silver/white marble-like markings.

    Key Feature
    Ornate silver-white "marble" or "painted" pattern on brown body. One of the most visually striking ticks. Short, blunt mouthparts (unlike blacklegged's longer parts).
    Size
    Largest common tick in eastern US. Adults 5mm unfed, up to 15mm engorged. Much larger than blacklegged tick — easy to spot.
    Where Found
    Grassy areas, roadsides, trails, camping areas. Less dependent on dense forest than blacklegged. Often found near roads and well-used paths.

    What CDC says it can carry

    “Tularemia and Rocky Mountain spotted fever.”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Geographic Range
    East of the Rocky Mountains throughout the eastern US. Also found on Pacific Coast. Most abundant in eastern half of US.
    Peak Activity
    Spring and early summer are peak.
    Found this tick on you? Start the tick-bite walkthrough

  • Western Blacklegged Tick

    Ixodes pacificus · Ixodidae · Hard Tick

    The West Coast equivalent of the deer tick. Virtually identical in appearance but with a slightly more oval body. Found in every Pacific Coast state.

    vs. Deer Tick
    Nearly identical to blacklegged tick. Slightly more oval body shape. Geographic location is the primary differentiator — if you're on the West Coast, it's I. pacificus.
    Key Differentiator
    Geography. CDC places it along the Pacific coast, particularly northern California — a deer-tick look-alike found there is most likely this species.

    What CDC says it can carry

    “Anaplasma phagocytophilum (anaplasmosis), Borrelia burgdorferi (Lyme disease), and B. miyamotoi (hard tick relapsing fever).”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Geographic Range
    Along the Pacific coast of the United States, particularly northern California (CDC).
    Peak Activity
    Adults most active in fall and winter in CA. Year-round in mild climates.
    Found this tick on you? Start the tick-bite walkthrough

  • Brown Dog Tick

    Rhipicephalus sanguineus · Ixodidae · Hard Tick

    The only tick that can complete its entire life cycle indoors, so it can be found year-round in kennels and homes with dogs. Elongated, plain reddish-brown with no markings. Feeds mainly on dogs, and also bites people.

    Unique Feature
    ONLY tick that can breed and survive entirely indoors. Found in dog kennels, between wall cracks, under rugs, and in furniture. Present year-round in homes.
    Appearance
    Uniformly plain reddish-brown — NO markings or patterns. Elongated, narrow body (unlike the round Lone Star). Short, thick hexagonal mouthparts.

    What CDC says it can carry

    “Rocky Mountain spotted fever (in the southwestern U.S. and along the U.S.-Mexico border).”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Geographic Range
    Worldwide — found in every state, particularly in warmer climates. Indoor environments year-round anywhere.
    If Found Indoors
    Finding brown dog ticks inside indicates a serious infestation. Treat the dog AND the home environment — they can hide in cracks, furniture, and baseboards.
    Found this tick on you? Start the tick-bite walkthrough

  • Rocky Mountain Wood Tick

    Dermacentor andersoni · Ixodidae · Hard Tick

    The western counterpart to the American dog tick. Very similar ornate appearance.

    vs American Dog
    Nearly identical to American dog tick. Geographic location is the primary differentiator. Rocky Mountain states = D. andersoni. East of Rockies = D. variabilis.

    What CDC says it can carry

    “Rocky Mountain spotted fever, Colorado tick fever, and tularemia.”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Geographic Range
    Rocky Mountain states — Montana, Idaho, Wyoming, Colorado, Utah, Nevada, and parts of Pacific Northwest. Elevations 4,000–10,000 feet common.
    Peak Activity
    Adults active when temperatures warm in spring.
    Found this tick on you? Start the tick-bite walkthrough

  • Gulf Coast Tick

    Amblyomma maculatum · Ixodidae · Hard Tick

    Found along the Gulf Coast and southeastern states. Similar appearance to the Lone Star tick but larger and without the prominent white dot. Expanding its range inland.

    Key Feature
    Larger than Lone Star. Similar long mouthparts. Pale ornamentation on body but NO single white star dot. Associated with coastal and open grassland habitats.
    Range
    Gulf Coast states (TX, LA, MS, AL, FL) and Atlantic coastal states. Expanding inland along river corridors. Found in open grasslands and coastal scrub.

    What CDC says it can carry

    “Rickettsia parkeri rickettsiosis, a form of spotted fever.”

    Source: CDC, Where Ticks Live, read 10 October 2026.
    Found this tick on you? Start the tick-bite walkthrough

  • Asian Longhorned Tick

    Haemaphysalis longicornis · Ixodidae · Hard Tick · INVASIVE SPECIES

    First detected in the US in 2017. CDC lists it in 20 states as of April 2024, and it is still spreading. Uniquely, females reproduce without mating (parthenogenesis), meaning a single tick can establish a population. Can infest livestock in enormous numbers.

    Key Concern
    Can reproduce without mating — a single female can establish a whole population. Can overwhelm livestock.
    Appearance
    Small, reddish-brown, no distinctive markings. Similar to blacklegged tick but slightly rounder. Hard to distinguish from common species without microscopy.

    What CDC says it can carry

    “In other countries, pathogens spread via bites from these ticks can make people and animals seriously ill.”

    “With ongoing testing of ticks collected in the United States, it is likely that some ticks will be found to contain pathogens that can be harmful to people. However, we do not yet know if and how often these ticks are able to pass these pathogens along to people and make them ill.”

    “Another laboratory study found that this tick has the ability to carry and spread the bacteria that causes Rocky Mountain spotted fever (Rickettsia rickettsii). The bacteria that cause Rocky Mountain spotted fever have not yet been found in these ticks in nature.”

    Source: CDC, Where Ticks Live, read 10 October 2026.

    Range & activity

    Current Range
    As of 12 April 2024, CDC lists Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia and West Virginia. First found in New Jersey (2017).
    Report It
    If you find what you believe is an Asian longhorned tick, report it to your state health department or USDA APHIS. Early reporting helps track the spread.
    Found this tick on you? Start the tick-bite walkthrough

  • Soft Tick

    Ornithodoros spp. (multiple species) · Argasidae · Soft Tick · Very Different

    A fundamentally different type of tick. No hard shield (scutum) — leathery, wrinkled body. Mouthparts on ventral (bottom) surface, not visible from above. Bites quickly and detaches. Often found in rodent nests, animal shelters, and rustic cabins.

    How to Recognize
    Leathery, wrinkled body — looks almost like a dried raisin or pumpkin seed. NO visible head from above — mouthparts hidden underneath. No hard shell. Looks very different from hard ticks.
    Fast Feeder
    Feeds quickly (vs. days for hard ticks). Often bites at night while people sleep. Bite may go unnoticed. Found in caves, cabins, rodent burrows.

    What CDC says it can carry

    “STRF is caused by Borrelia hermsii, B. turicatae, and other Borrelia bacteria, transmitted to humans through the bite of infected soft-bodied ticks of the genus Ornithodoros.”

    Source: CDC, About Soft Tick Relapsing Fever (STRF), read 10 October 2026.

    Range & activity

    Where Found
    Rustic cabins, caves, animal burrows at higher elevations in the western US. O. hermsi in mountain cabins (Pacific states). O. turicatae in the south.
    Found this tick on you? Start the tick-bite walkthrough

You’ve identified it — now what?

Save the tick. A sealed bag with a scrap of damp paper towel is enough. Note the date and where on your body it was attached. How tick testing works
Write down the date. Testing too early returns a negative regardless of whether you were infected, so the date of the bite is what tells your provider whether a result means anything. The seronegative window
Do not wait on identification if you are unwell. Fever with a severe headache, a spreading rash, confusion, weakness that is new or spreading, trouble breathing, or chest pain after a tick bite needs care now — the species can be settled later.
Get Urgent Care Guidance

Identified it, saved it, written the date down? The tick-bite walkthrough takes you through the rest, and its last step adds a reminder to your own calendar.

Start the tick-bite walkthrough
What isn’t known

Lone star range is changing faster than the maps.

What to do · a toolStart the tick-bite workflow — record engorgement and timing as facts →
What to ask a clinician
  • Given this species and county, what would you want to know from me over the next month?
  • If weakness, confusion or trouble breathing starts in the weeks after a bite, who do I call the same day?
Find a Lyme-Literate Provider
Related
Review statePending clinical review

Which species carries which pathogen, and what the page says a bite from each one does and does not mean. A clinically-informed reviewer has not yet signed this off, and it stays marked until one does.

Educational information, not medical advice.