What size is a tick when it is engorged with blood? - briefly
An engorged female tick typically expands to about 5–10 mm in length, while larger species such as the American dog tick can reach up to 2 cm when fully saturated with blood.
What size is a tick when it is engorged with blood? - in detail
A fully fed tick can increase its body size dramatically compared with its unfed state. The magnitude of expansion depends on species, developmental stage, and the host’s blood volume.
Adult females of the deer tick (Ixodes scapularis) typically measure 2–3 mm in length when unfed. After a complete blood meal they stretch to 10–12 mm long and 5–6 mm wide, with a weight of 150–200 mg—approximately a 100‑fold increase. The lone‑star tick (Amblyomma americanum) grows from 3–4 mm to 12–14 mm in length and 5–7 mm in width, weighing up to 250 mg. The American dog tick (Dermacentor variabilis) expands from 3–4 mm to 8–10 mm long, 4–5 mm wide, and can reach 300 mg.
Nymphs and larvae also engorge, though to a lesser extent. A nymph of Ixodes ricinus rises from 1 mm to 4–5 mm in length, while a larva of the same species expands from 0.5 mm to about 2 mm. Weight gains for these stages range from 30‑to‑80 mg.
Key factors influencing final dimensions:
- Host size and blood pressure: Larger hosts supply more blood, allowing greater expansion.
- Attachment duration: Longer feeding periods (typically 3–7 days for adults) result in larger engorgement.
- Species‑specific anatomy: Some ticks possess a more elastic cuticle, permitting greater elongation.
Measurements are usually taken with a stereomicroscope equipped with an ocular micrometer, reporting length and width in millimetres and weight in milligrams. In imperial units, fully engorged adult females range from 0.4 to 0.6 inches long and weigh 0.005 to 0.010 ounces.