Blacklegged tick (Ixodes scapularis)

• Adult female: brown to reddish-orange body with a solid, dark brown-to-black shield (scutum) right behind the mouthparts. The shield is plain, with no markings (inornate). It stands out sharply against the bare orange-red rear of the body.
• Adult male: smaller and dark brown all over. The shield covers nearly the whole back, with no reddish color.
• Dark brown-to-black legs, a helpful clue in the field.
• No single white dot, which rules out the female Lone Star tick. No pale, mottled shield pattern, which rules out the American dog tick.
• Nymph: tiny (about a poppy seed), pale tan with a small dark shield. Nymphs cause most disease spread to people.

Established across the eastern half of the United States. It is most common in three areas: the Northeast and mid-Atlantic (from Maine down through Virginia); the upper Midwest and north-central states, notably Minnesota, Wisconsin, and Michigan; and parts of the Southeast. Its range is known to be spreading north and west. On the Pacific Coast, a close relative takes its place: the western blacklegged tick (Ixodes pacificus). This range is different from the Lone Star tick's, which is more southeastern and south-central.

Tick presence is not the same as personal disease risk. Not every bite transmits a pathogen.

• Lyme Disease
• Anaplasmosis
• Babesiosis
• Powassan virus disease
• Ehrlichiosis

The western blacklegged tick (Ixodes pacificus) looks almost the same but lives on the Pacific Coast, so location is the main clue. Other small Ixodes ticks can be hard to tell apart without a magnifier. The blacklegged tick differs from the female Lone Star tick because it has no white dot. It differs from the American dog tick and Rocky Mountain wood tick (Dermacentor) in three ways. It is smaller, it has dark legs, and its shield is plain and dark, not pale and mottled. Unfed nymphs are the easiest stage to miss or get wrong, so save any tick you remove so it can be identified.