What does a tick look like and what are its dimensions? - briefly
A tick is a small, oval arachnid with a flattened, reddish‑brown body, bearing six legs in the larval stage and eight legs as an adult. Unfed adults measure 3–5 mm in length and can expand to roughly 10 mm after feeding.
What does a tick look like and what are its dimensions? - in detail
Ticks are small arachnids with a compact, oval or slightly elongated body that tapers toward the rear. The dorsal surface, called the scutum, is a hard plate in adult females and a flexible shield in males and immature stages. Legs are eight in number, relatively long compared to body size, and positioned near the front, giving the animal a characteristic “spider‑like” silhouette. Mouthparts consist of a short, beak‑like structure (the capitulum) that projects forward and is used for piercing skin and feeding.
Size varies widely among species and developmental stages:
- Egg: 0.5 mm in length, spherical, smooth surface.
- Larva (seed tick): 0.5–0.8 mm long, 0.2–0.3 mm wide; lacks a scutum, appears translucent.
- Nymph: 1.0–2.5 mm long, 0.5–1.0 mm wide; possesses a partial scutum, often reddish after a blood meal.
- Adult female: 2.0–6.0 mm long (unfed), expanding to 10–12 mm when engorged; width 2.0–3.5 mm (unfed) up to 8–10 mm engorged; scutum covers the entire dorsal surface.
- Adult male: 2.0–4.0 mm long, 2.0–3.0 mm wide; scutum occupies most of the dorsum, does not expand significantly after feeding.
Species differences affect dimensions. For example, the American dog tick (Dermacentor variabilis) typically reaches 3–4 mm unfed, while the lone star tick (Amblyomma americanum) may grow to 5 mm. The tropical brown dog tick (Rhipicephalus sanguineus) often remains under 3 mm when unfed.
Morphologically, ticks possess a pair of sensory organs (Haller’s organs) on the first pair of legs, used to detect host cues such as carbon dioxide, heat, and movement. The ventral side bears a series of plates (ventral plates) that protect internal organs. Coloration ranges from pale beige in larvae to dark brown or reddish hues in engorged adults, reflecting blood intake.
Overall, ticks present a compact, shielded body with eight legs and a specialized mouthpart, and their dimensions span from less than a millimeter in the earliest stage to over a centimeter in a fully engorged adult female, depending on species and feeding status.