Tick

Ticks are arachnids in the order Ixodida, related to spiders and mites, and are external parasites that feed on the blood of vertebrate hosts. The American dog tick, a widely encountered hard tick species, exemplifies the general body plan and biology shared across many common tick species: a flattened, oval, unsegmented body armored with a tough dorsal plate (scutum).

Ticks lack wings and cannot jump or fly; instead, they use a behavior called "questing," climbing to the tips of grass or low vegetation and extending their front legs to grasp onto a passing host. Their biology is entirely centered around periodic blood meals, which fuel each life stage's molt to the next.

As obligate blood-feeding parasites, ticks are a notable component of many terrestrial ecosystems, interacting with a wide range of mammal, bird, and reptile hosts throughout their multi-stage life cycle.

• Flattened, oval, unsegmented body, brownish to reddish-brown, with a hard dorsal shield (scutum) that may bear pale markings in some species.
• Eight legs in adults and nymphs (only six in the larval stage), lacking antennae or wings.
• Body dramatically expands and turns gray or bluish in color once engorged with a blood meal, sometimes many times its unfed size.
• Mouthparts are visible at the front of the body when viewed from above, adapted for piercing skin and attaching for extended feeding.
• Lookalikes: deer tick/black-legged tick (notably smaller and darker, with a uniformly dark, unmarked scutum) and other hard tick species; overall size, shield markings, and host association help narrow identification.

Ticks are found in a wide range of temperate and warmer climates worldwide, favoring tall grass, brushy vegetation, woodland edges, and trails frequented by potential hosts such as deer, rodents, and other mammals. Many species are most active from spring through fall, with activity peaks varying by region and species.

They typically remain low in vegetation, climbing blades of grass or shrubs to a height suited for contacting passing hosts, and seek humid microhabitats such as leaf litter to avoid drying out between active questing periods.

Ticks are obligate blood feeders, relying on this diet at each active life stage to fuel growth and molting or, in adults, reproduction. They locate hosts primarily through questing behavior, sensing carbon dioxide, heat, and vibrations from a perched position on vegetation rather than actively pursuing prey.

Once attached, a tick can remain feeding on a host for an extended period, several days in many species, before detaching. They are generally slow-moving and do not jump or fly, relying entirely on host contact for movement between locations, and they play a role in many ecosystems as parasites of a broad range of vertebrate hosts.

Female ticks lay large batches of eggs, often numbering in the thousands, in a sheltered location such as leaf litter. Eggs hatch into six-legged larvae, which seek a first blood meal, then molt into eight-legged nymphs that seek a second host and blood meal before molting into adults.

Adults seek a final host for a blood meal and mating before females lay eggs, completing the cycle. Depending on species and climate, the full life cycle from egg to adult can take from several months up to a few years, with development often occurring across multiple host encounters and seasons, and some species overwintering in an unfed stage between hosts.