Ticks of the U.S.

Size:

Small, a sesame seed (nymph: a poppy seed)

Look for:

Reddish-orange body, solid dark shield, black legs, no pattern

Carries:

Lyme, babesiosis, anaplasmosis, Powassan

Size:

Larger, an apple seed

Look for:

Brown with an ornate off-white mottled shield

Carries:

Rocky Mountain spotted fever, tularemia (rare)

Size:

Medium, rounded

Look for:

Reddish-brown; female has a single white dot on the back

Carries:

Ehrlichiosis, STARI, alpha-gal syndrome

Found nationwide, the one tick that infests homes and kennels indoors

Size:

Medium, narrow body that tapers toward the head

Look for:

Uniform reddish-brown, no ornate markings

Carries:

Rocky Mountain spotted fever, canine diseases

A southern tick spreading north into the mid-Atlantic

Size:

Large, bigger than a lone star

Look for:

Silvery ornate markings on the shield, no single dot

Carries:

Rickettsia parkeri spotted fever

A newer arrival, established in the mid-Atlantic and spreading north

Size:

Small and plain, often found in large numbers

Look for:

Reddish-brown with no markings

Carries:

Mainly a livestock threat; human disease risk under study

The main human-biting tick of the interior West, a spring tick at 4,000 to 10,500 ft

Size:

Larger, an apple seed

Look for:

Brown with an ornate off-white and gray marbled shield

Carries:

Rocky Mountain spotted fever, Colorado tick fever, tularemia

California's most common human-biting tick, in chaparral and brush

Size:

Larger, an apple seed

Look for:

Brown with a marbled silvery-gray ornate shield

Carries:

Pacific Coast tick fever, tularemia