Blacklegged Tick

The blacklegged tick, widely known as the deer tick, is a small hard tick found throughout the eastern and upper midwestern United States. It is far smaller than the American dog tick and lacks any ornate markings, appearing as a plain, glossy, teardrop-shaped arachnid with distinctly dark legs contrasting against its reddish-brown to orange body.

As a three-host tick, it relies on different hosts at each life stage, with larvae and nymphs commonly feeding on white-footed mice and other small mammals, and adults often found on deer, though they will also attach to a wide range of birds and mammals. Its small size, particularly at the nymph stage, makes it easy to overlook on skin or clothing.

This species is active across an unusually wide temperature range, with adults sometimes questing on mild winter days when other ticks are dormant, making it one of the more persistently active ticks in its range.

• Small, teardrop-shaped body with a plain reddish-brown to orange abdomen and noticeably dark, almost black legs.
• No ornate pattern on the scutum, unlike the American dog tick; males have a solid dark brown to black shield covering most of the body.
• Adult females measure about 3-4 mm unfed, swelling to roughly 10 mm when engorged; nymphs are poppy-seed sized at under 2 mm.
• Eight legs as nymphs and adults; six legs at the larval stage.
• Lookalikes include other Ixodes species, distinguished mainly by range and subtle mouthpart structure.

Blacklegged ticks favor humid, shaded environments such as deciduous and mixed woodlands, leaf litter, and the brushy transition zones between forest and open field. They are widespread across the eastern United States from the upper Midwest to New England and south along the Atlantic coast. Nymphs are most active in late spring through summer, while adults quest primarily in fall and again in early spring, sometimes even during winter thaws.

This tick is a generalist parasite, feeding on a broad range of hosts including small rodents, birds, deer, and other mammals depending on life stage. Like other hard ticks, it quests by climbing onto low vegetation or leaf litter and extending its legs to grasp a passing host, relying on scent, heat, and carbon dioxide cues rather than vision. Ecologically, it plays a role in regulating small mammal and deer populations indirectly through its position in the food web and is preyed upon by birds and some invertebrates.

After a blood meal, females lay a single large batch of eggs on the ground and then die. Eggs hatch into six-legged larvae that feed once on a small host, typically a mouse, before molting into nymphs. Nymphs feed on a wider range of hosts and molt into adults, which seek a larger host for a final meal and to mate. The complete life cycle generally spans about two years, with the tick overwintering in leaf litter between active feeding periods.