LymeHQ · Field Reference

Tick identification

Which tick bit you determines which diseases are even possible — and the species that carries Lyme is not the one most people picture. Nine species, what distinguishes each, and what each one actually transmits.

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.
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.

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. The nymph that transmits most Lyme is about the size of a poppy seed, not the engorged adult in most photographs. If you are looking for something obvious, you will miss it.

What a tick carries is not just Lyme

Three of the ticks that bite people in the United States, and what each one is commonly associated with.

Tick species and the infections each one is associated withTick species, each with the infections it is commonly associated with. The blacklegged tick: Lyme, babesiosis, anaplasmosis and Powassan. The lone star tick: ehrlichiosis, alpha-gal, STARI and tularemia. The American dog tick: Rocky Mountain spotted fever and tularemia. Tularemia therefore appears twice, because two of these species carry it. A single bite can pass on more than one of these, and each list names common associations rather than every possibility.Blacklegged tickLymeBabesiosisAnaplasmosisPowassanLone star tickEhrlichiosisAlpha-galSTARITularemiaAmerican dog tickRocky Mountainspotted feverTularemiaTularemia appears on two rows:two of these species carry it.

A single bite can pass on more than one of these.

Which is why testing for Lyme alone can miss what is actually making you ill.

A tick does not necessarily carry any of these, and which ticks live where varies by region. These are the commonly named associations rather than a complete list — orientation, not a diagnosis.

Species-to-disease associations: US Centers for Disease Control and Prevention, tickborne diseases of the United States. Common associations, not an exhaustive list; nothing on this drawing is a measured quantity.

The one that bites you is the size of a poppy seed.

The three tick life stages drawn at their true relative sizeThree life stages of the same tick, drawn to one scale so they can be compared. The larva is the smallest, has six legs, and rarely carries an infection. The nymph is roughly the size of a poppy seed and is behind most human cases. The adult is roughly the size of a sesame seed, several times larger again, and correspondingly easier to notice. The stage responsible for most illness is the one hardest to see.DRAWN TO RELATIVE SCALELarvaRarely infectedSix legsNymphMost human casesPoppy-seed sizedAdultEasier to spotSesame-seed sized

Nymphs are out when people are, and small enough to miss entirely.

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 the poppy-seed / sesame-seed size comparisons: US Centers for Disease Control and Prevention, tick life cycle and tick identification. The three silhouettes are drawn to scale against one another; no absolute measurement is shown.

The nine species

Ordered by how often they bite people in North America. 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

    🔴 Critical Risk — Primary Lyme vector

    The most important tick for Lyme disease in the eastern US. Responsible for transmitting more tick-borne pathogens than any other species in North America. The tiny nymph stage — barely visible — causes the majority of human infections.

    Size
    Adult: 2–3mm unfed (sesame seed). Nymph: 1.5mm (poppy seed). Engorged: up to 10mm.
    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.
    Danger Stage
    Nymph (May–July) is most dangerous — nearly invisible, active when humans are outdoors most. Causes ~75–90% of Lyme transmissions.

    Diseases transmitted

    • 🎯 Lyme Disease (Borrelia burgdorferi)
    • 🩸 Babesiosis (B. microti)
    • ⚡ Anaplasmosis (HGA)
    • 🧠 Powassan Virus
    • 🔄 B. miyamotoi (relapsing fever)
    • ◎ Ehrlichia muris eauclairensis

    ✕ Does NOT transmit Rocky Mountain Spotted Fever

    Range & activity

    Geographic Range
    Eastern US (Maine to Florida), Upper Midwest (Wisconsin, Minnesota). Expanding westward. Highest density: Northeast and Mid-Atlantic.
    Peak Activity
    Nymphs: May–July (highest risk). Adults: October–November and March–May. 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.
    Transmission Time
    More than 24 hours for Lyme, in most cases. As little as 15 minutes for Powassan virus. Remove promptly.

  • Lone Star Tick

    Amblyomma americanum · Ixodidae · Hard Tick

    🟡 High Risk — Aggressive hunter

    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. Rapidly expanding its range 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).

    Diseases transmitted

    • ⚡ Ehrlichiosis (E. chaffeensis, E. ewingii)
    • 🥩 Alpha-gal Syndrome (red meat allergy)
    • 🦠 Tularemia
    • ◎ STARI (Southern Tick-Associated Rash Illness)
    • 🩸 Heartland Virus
    • 🔄 Bourbon Virus

    ✕ Does NOT transmit Lyme disease (B. burgdorferi) — but causes STARI, a similar illness

    Range & activity

    Geographic Range
    Traditionally southeastern US but now found as far north as Maine and as far west as central Texas. Expanding rapidly due to climate change.
    Peak Activity
    March through October in most areas. Year-round in far south. Most active when temperatures exceed 70°F.
    Alpha-gal Warning
    Bites from Lone Star ticks can trigger a lifelong allergy to red meat (beef, pork, lamb) that develops weeks after the bite. Symptoms are delayed 2–6 hours after eating mammalian products.
    STARI Note
    STARI causes a bull's-eye rash that looks identical to Lyme's EM rash — but standard Lyme tests are negative. If you have a rash and a negative Lyme test, STARI may be the explanation.

  • American Dog Tick

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

    🟡 High Risk — RMSF primary vector

    The largest common tick in the eastern US. Unmistakable ornate silver/white marble-like markings. The primary vector for Rocky Mountain Spotted Fever — one of the most dangerous tick-borne diseases. Despite the name, transmits to humans frequently.

    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.
    Common Mistake
    American dog ticks are NOT vectors for Lyme disease — this is a common misconception. A positive bite does not mean Lyme risk, but RMSF risk is serious.

    Diseases transmitted

    • 🌡️ Rocky Mountain Spotted Fever (R. rickettsii)
    • 🦠 Tularemia (Francisella tularensis)
    • ◎ Rickettsia parkeri rickettsiosis

    ✕ Does NOT transmit Lyme disease — a common and important misconception

    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 (April–June) are peak. Adults most common April–August.

  • Western Blacklegged Tick

    Ixodes pacificus · Ixodidae · Hard Tick

    🔴 Critical Risk — West Coast Lyme vector

    The West Coast equivalent of the deer tick. Virtually identical in appearance but with a slightly more oval body. The primary Lyme vector for patients in California, Oregon, and Washington. 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
    Found ONLY on the West Coast. If you find what looks like a deer tick in California, Oregon, or Washington, it's Western blacklegged.

    Diseases transmitted

    • 🎯 Lyme Disease (Borrelia burgdorferi)
    • ⚡ Anaplasmosis (A. phagocytophilum)
    • 🩸 Babesiosis (B. duncani — West Coast variant)

    Range & activity

    Geographic Range
    Pacific Coast from Baja California to British Columbia. Found in every West Coast state. Also in some western mountain states.
    Peak Activity
    Adults most active in fall and winter (Oct–April) in CA. Nymphs peak April–July. Year-round risk in mild climates.

  • Brown Dog Tick

    Rhipicephalus sanguineus · Ixodidae · Hard Tick

    🟢 Moderate Risk — Indoor threat

    The only tick that can complete its entire life cycle indoors — making it a year-round threat in kennels and homes with dogs. Elongated, plain reddish-brown with no markings. Primarily feeds on dogs but will bite humans when infestations are heavy.

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

    Diseases transmitted

    • 🌡️ Rocky Mountain Spotted Fever (in warm climates)
    • ◎ Canine ehrlichiosis (to dogs primarily)

    ⚠️ Primarily a threat to dogs — rarely bites humans unless heavy indoor infestation

    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.

  • Rocky Mountain Wood Tick

    Dermacentor andersoni · Ixodidae · Hard Tick

    🟡 High Risk — Western RMSF vector

    The western counterpart to the American dog tick. Very similar ornate appearance. Also transmits Rocky Mountain Spotted Fever and can cause tick paralysis — a rare condition where the tick's saliva causes progressive paralysis that reverses upon tick removal.

    Unique Danger
    Can cause tick paralysis — ascending paralysis from saliva neurotoxins. Symptoms reverse completely upon tick removal. Most dangerous if attached to scalp or behind ears.
    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.

    Diseases transmitted

    • 🌡️ Rocky Mountain Spotted Fever
    • 🦠 Tularemia
    • ⚡ Tick Paralysis (neurotoxin in saliva)
    • ◎ Colorado Tick Fever (virus)

    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
    April through June at higher elevations. Adults active when temperatures warm in spring.

  • Gulf Coast Tick

    Amblyomma maculatum · Ixodidae · Hard Tick

    🟡 High Risk — Rickettsia vector

    Found along the Gulf Coast and southeastern states. Similar appearance to the Lone Star tick but larger and without the prominent white dot. Can transmit a distinct Rickettsia species that causes spotted fever. 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.

    Diseases transmitted

    • 🌡️ Rickettsia parkeri Rickettsiosis
    • ⚡ Hepatozoon americanum (to dogs)

  • Asian Longhorned Tick

    Haemaphysalis longicornis · Ixodidae · Hard Tick · INVASIVE SPECIES

    🔴 Invasive — Expanding threat

    First detected in the US in 2017. Now found in 20+ states and spreading rapidly. Uniquely, females reproduce without mating (parthenogenesis), meaning a single tick can establish a population. Can infest livestock in enormous numbers. Disease risk still being assessed.

    Key Concern
    Can reproduce without mating — a single female can create thousands of offspring. Can overwhelm livestock. In Asia, transmits severe fever with thrombocytopenia syndrome (SFTS) virus — fatal in 5–30% of cases.
    Appearance
    Small, reddish-brown, no distinctive markings. Similar to blacklegged tick but slightly rounder. Hard to distinguish from common species without microscopy.

    Diseases transmitted

    • ⚡ Spotted fever group Rickettsia
    • ◎ Anaplasma phagocytophilum (confirmed in some ticks)
    • 🔄 Potential: SFTS virus (in Asia, not confirmed US)

    ⚠️ US disease risk still under active research by CDC

    Range & activity

    Current Range
    20+ eastern states. First found in New Jersey (2017). Now confirmed in Virginia, West Virginia, Maryland, Pennsylvania, New York, Connecticut, and expanding rapidly south and west.
    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.

  • Soft Tick

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

    🟢 Moderate Risk — Relapsing fever

    A fundamentally different type of tick. No hard shield (scutum) — leathery, wrinkled body. Mouthparts on ventral (bottom) surface, not visible from above. Bites quickly (minutes) 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 in minutes (vs. days for hard ticks). Often bites at night while people sleep. Bite may go unnoticed. Found in caves, cabins, rodent burrows.

    Diseases transmitted

    • 🔄 Tick-Borne Relapsing Fever (Borrelia hermsii, B. turicatae)
    • ◎ Q Fever (Coxiella burnetii) — some species

    ✕ Does NOT transmit Lyme disease or RMSF

    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.
    Relapsing Fever
    Causes recurring fever episodes (relapsing pattern) separated by days of feeling better. Treatable with doxycycline. Report tick exposure when seeking care.

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. Many labs will test it, and that result arrives faster than your own antibodies will. 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, or chest pain after a tick bite needs care now — the species can be settled later.

Want us to remind you to check?

Identified it, saved it, written the date down? What remains is a month of remembering to check your skin. We’ll email you three times — around day 7, day 14 and day 30 after today — because that brackets the window when a rash would actually appear. No account, nothing to install.

Reminders are not switched on in this build yet — the sending half is not configured, so nothing here collects an address until it is.

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