LoneStarMapTick species • Field guide
Gulf Coast tick (Amblyomma maculatum)
The Gulf Coast tick (Amblyomma maculatum) is a medium-to-large, ornately patterned hard tick historically tied to the Gulf of Mexico and southern Atlantic coasts, whose established range is now spreading well inland and up the East Coast. Adults are dark brown with striking silvery-white markings on the shield (scutum) and long, rectangular mouthparts. In the United States it is the principal vector of Rickettsia parkeri rickettsiosis — a spotted-fever illness that is generally milder than Rocky Mountain spotted fever. It is not a primary vector of Rocky Mountain spotted fever, and it does not spread Lyme disease, ehrlichiosis, anaplasmosis, or the other common US tick-borne diseases. This page is educational and is not medical advice.
Last reviewed: 2026-07-20 · Educational only — not medical advice.
How to identify it
- Adult female: dark reddish-brown body with a reduced, dark shield (scutum) behind the head bearing ornate silvery-white markings — one median plus two lateral interrupted stripes — not a single round dot.
- Adult male: the ornate shield covers the entire back, dark brown laced with a connected network of silvery-white lines.
- Long, rectangular mouthparts (an Amblyomma trait) — much longer than the short, stubby, pyramid-shaped mouthparts of the American dog tick.
- Eyes set along the sides of the shield and festoons (small ridges) along the rear body margin; overall a large tick, noticeably bigger than a blacklegged (deer) tick.
- Immature stages (larvae and nymphs) are small and largely unmarked — the bold silvery ornamentation is an adult feature.
Size: Larvae ('seed ticks') are about 0.5 mm with six legs; unfed nymphs are roughly 1.3 x 0.75 mm; unfed adults are about 6 mm (~1/4 inch) — clearly larger than a deer tick — and an engorged female can swell to roughly 1/2 inch (10+ mm) or more.
Where it lives & when
Historically a coastal tick of the Gulf of Mexico and southern Atlantic shorelines — roughly a 100-150 mile inland band from Texas east across the Gulf states to Florida and up to South Carolina. Established inland populations now reach Oklahoma, Kansas, Arkansas, Missouri, Kentucky, Illinois, and Indiana, and documented northeastward establishment extends up the Atlantic seaboard through Maryland, Delaware, New Jersey, New York (including restored grasslands on Staten Island) and into Connecticut. This is the Gulf Coast tick's own vector range — a coastal-plus-mid-continent distribution distinct from, and not to be equated with, the Lone Star tick's.
Season: Adults — the life stage that bites people — are most active in the warm months, broadly spring through early fall. Timing shifts by region: near year-round activity is reported along the warm Gulf coast, while inland populations (for example in Oklahoma and Kansas) run roughly February-October and northern Florida populations roughly February-September.
- Open grassland and prairie, coastal uplands, and transitional field-to-forest edges
- Overgrown fields, pastures, and reclaimed grassy lots — including urban grasslands in newly colonized northeastern cities
- Drier, sunnier grassy sites; less tied to dense shaded woodland than the Lone Star tick
Diseases the gulf coast tick can carry
No major human disease is firmly established for this species in the U.S. Prevent bites regardless.
Look-alikes
Most easily confused with its close relative the Lone Star tick (also an Amblyomma with long mouthparts) — but a Gulf Coast female shows ornate silvery striping spread across the shield rather than the Lone Star female's single round white 'lone star' dot. It is also mistaken for the American dog tick, which is likewise ornate; separate them by the Gulf Coast tick's long, rectangular mouthparts (the dog tick's are short and pyramid-shaped) and its larger, more extensively patterned shield. Immature larvae and nymphs are hard to tell apart by eye, so when in doubt have the specimen identified.
Compare all tick species →Gulf Coast tick — frequently asked questions
What disease does the Gulf Coast tick spread?+
In the United States it is the main carrier of Rickettsia parkeri rickettsiosis, a spotted-fever illness. It often begins with a dark scab (an eschar) at the bite site a few days to about a week later, followed by fever, headache, muscle aches, and rash. It is generally milder than Rocky Mountain spotted fever and responds to prompt doxycycline. See a clinician for evaluation — this page is educational, not medical advice.
Does the Gulf Coast tick cause Rocky Mountain spotted fever?+
No. Rocky Mountain spotted fever is caused by Rickettsia rickettsii and is spread mainly by the American dog tick, Rocky Mountain wood tick, and brown dog tick. The Gulf Coast tick transmits a different, usually milder spotted fever caused by Rickettsia parkeri.
How do I tell a Gulf Coast tick from a Lone Star tick?+
Both are Amblyomma ticks with long mouthparts, so check the shield: a Gulf Coast female has ornate silvery-white striping across the back, while a Lone Star female has a single round white dot in the center. Gulf Coast ticks also tend to run a little larger.
Where are Gulf Coast ticks found?+
Traditionally along the Gulf of Mexico and southern Atlantic coasts from Texas to South Carolina, but established populations now extend inland to states such as Oklahoma, Kansas, Arkansas, and Missouri and up the East Coast as far as Connecticut.
Sources used
- TickEncounter Resource CenterUniversity of Rhode Island
Tick identification, prevention, and reporting resources.
- Where Ticks LiveCDC
The Lone Star tick is widely distributed in the Northeast, South, and Midwest U.S.
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Gulf Coast tick (Amblyomma maculatum)
Identify the Gulf Coast tick by its ornate silvery-striped shield and long mouthparts, learn its coastal-and-expanding US range and life stages, and see the main illness it spreads to people — Rickettsia parkeri rickettsiosis, a milder spotted fever, not RMSF or Lyme. Educational, not medical advice.