What do ticks that cause Lyme disease look like? - briefly
The Lyme‑disease tick (Ixodes scapularis or I. pacificus) is a flat, dark‑brown arachnid about 2–3 mm long, roughly the size of a grain of rice. After feeding it expands and turns a reddish‑brown, balloon‑like appearance.
What do ticks that cause Lyme disease look like? - in detail
The ticks responsible for transmitting the bacterium that causes Lyme disease belong to the genus Ixodes, primarily Ixodes scapularis in eastern North America and Ixodes pacificus on the West Coast. Their appearance changes with life stage and feeding status.
Unfed stages
- Larva: Approximately 0.5 mm in length, translucent or pale beige, lacking a hard dorsal shield (scutum). Six legs are visible.
- Nymph: 1.5–2 mm long, reddish‑brown, with a small, dark scutum covering only the anterior portion of the body. Six legs remain.
- Adult female: 3–5 mm when unfed, dark brown to black, large oval scutum covering the entire dorsal surface, eight legs. Abdomen appears rounded and unengorged.
- Adult male: Similar size to the female but with a slightly smaller scutum that does not extend to the posterior, a more tapered abdomen, and a visible genital opening.
Engorged stages
- Larva: Swells to about 2 mm, becomes opaque and lighter in color.
- Nymph: Expands to 4–5 mm, takes on a bluish or grayish hue, abdomen markedly distended.
- Adult female: Can reach 10 mm or more, abdomen turns a pale, almost translucent gray, surface appears smooth and stretched.
- Adult male: Rarely engorges; remains close to original size and coloration.
Key visual cues
- Presence of a hard, shield‑like scutum on the dorsal side.
- Eight legs in all stages after the larval molt; six legs in the larva.
- Distinctive “hourglass” pattern on the ventral side of adult females.
- Color transition from light, translucent in unfed larvae to darker, more opaque in nymphs and adults.
- Engorged females show a markedly enlarged, balloon‑like abdomen.
These morphological details enable reliable identification of Lyme‑disease vectors in the field and under laboratory examination.