What does a fully engorged tick look like? - briefly
A fully engorged tick looks like a swollen, balloon‑shaped arachnid, changing from brown to a gray‑blue hue and expanding several times its original size, with a smooth, glossy body. Its legs often retract, and the abdomen can reach up to 10 mm, resembling a small, translucent sack.
What does a fully engorged tick look like? - in detail
A fully engorged tick presents a markedly swollen, balloon‑like body that can be several times larger than its unfed state. The dorsal shield (scutum) remains a rigid plate on the anterior portion, but the posterior region, the idiosoma, expands dramatically as the insect fills with blood. The abdomen becomes rounded, often reaching a diameter of 5‑10 mm in common species such as the American dog tick (Dermacentor variabilis) and up to 12 mm in the lone star tick (Amblyomma americanum). The overall length may exceed 10 mm, giving the tick a grape‑like appearance.
Key visual features:
- Color: Dark brown to deep black when unfed; after engorgement the cuticle often turns reddish‑brown or grayish, sometimes with a glossy sheen due to the stretched cuticle.
- Surface texture: The cuticle appears stretched and smooth, lacking the fine hairs (setae) that are more visible on a flat, unfed specimen.
- Legs: Still visible, but positioned close to the swollen body; they may appear thin and pale compared to the enlarged abdomen.
- Mouthparts: The chelicerae and hypostome remain at the front, often protruding slightly as the tick remains attached to the host.
- Scutum: In hard‑tick species the scutum does not expand; it stays a small, flat plate covering only the anterior segment, creating a clear contrast between the rigid shield and the soft, bulging posterior.
Physiological changes accompany the visual transformation. The tick’s weight can increase by more than 100‑fold, and the internal organs are displaced outward, causing the abdomen to assume a translucent, gelatinous look. In soft‑tick families (e.g., Ornithodoros), the entire body expands uniformly, resulting in an oval, almost spherical shape without a distinct scutum.
These characteristics allow rapid identification of a tick that has completed a blood meal. Recognizing the enlarged, rounded silhouette, altered coloration, and the disproportion between the small scutum and the massive posterior region confirms that the parasite is fully engorged.