Ixodes scapularis Say, 1821

Black-legged tick

The sesame-seed-sized tick behind Lyme disease, check yourself after the woods, not your basement.

Order: Ixodida
Family: Ixodidae
Group: Ticks & mites
Ontario status: Established and expanding, Lyme risk areas across southern and eastern Ontario

Why it matters

It vectors Borrelia burgdorferi (Lyme disease), Anaplasma (anaplasmosis), Babesia (babesiosis), and Powassan virus. Lyme is the main concern in Ontario and it is preventable: the tick must feed for a day or more before the bacteria move. Check yourself, check kids, check dogs.

Origin

Native to eastern North America; its Ontario range is expanding northward as winters warm.

Behavior

Does not jump or fly, it climbs vegetation and waits with outstretched legs (questing), grabbing whatever brushes past. Feeds for days, then drops off. Most active in spring and fall.

Living conditions

Woodland edges, tall grass, leaf litter, and trails, not inside homes and not on mowed lawns. You meet it on hikes, at the cottage, or where the yard meets the woods.

Signs of presence

Ticks on clothing or pets after time in woods or tall grass
A tiny dark poppy-seed-sized speck attached to skin (nymph)
A larger tick with a reddish body attached behind ears, in armpits, or at the waistline
A spreading circular rash days after a bite, see a doctor and mention the tick

Weaknesses

Must feed for 24-36 hours to transmit Lyme, prompt removal breaks the chain
Desiccates quickly in dry, sunny, mowed areas; cannot survive on lawns
Vulnerable at every stage to desiccation and to being brushed off before attaching
Requires leaf litter and humidity, clearing leaf litter from yard edges removes its habitat

Myths and facts

Myth Ticks fall out of trees onto people.
Reality They quest from low vegetation, knee height at most. The danger zone is brushing through tall grass and leaf litter, not standing under trees.
Myth A tick bite means you will get Lyme disease.
Reality Transmission of Lyme bacteria typically requires 24-36 hours of attachment. A tick found and removed the same day is very unlikely to have transmitted it, but save the tick for identification.

Research notes

Morphology

Unfed nymph 1-2 mm (poppy seed); unfed adult female ~3 mm with distinctive orange-red abdomen behind a dark scutum; males smaller, dark. Eight legs as nymph/adult; mouthparts long and visible from above (Ixodes hallmark). Engorged females swell to ~10 mm.

Diagnostics

Inornate (unpatterned) dark scutum; long mouthparts; nymphs poppy-seed sized with 8 legs. Confirm with tick keys or public-health lab submission, Ontario public health accepts tick submissions for identification.

Easily confused with

American dog tick (Dermacentor variabilis) Dog ticks are larger with ornate white markings on the scutum; deer ticks are inornate and smaller.
Lone star tick (Amblyomma americanum) Lone star ticks have a single white spot (females); not established in Ontario.

Life cycle

Adult: Adults quest in fall and early spring; females lay 1,000-3,000 eggs in leaf litter and die
Egg: Eggs laid in spring in moist leaf litter; hatch in weeks
Egg to adult: Typically 2 years in Ontario; 3 years in colder zones
Generations per year: One generation spans 2-3 years
Nymph or larva: Larva feeds once (summer), molts to nymph; nymph feeds once (spring-summer, the peak Lyme-transmission stage), molts to adult

Development

Egg to six-legged larva to eight-legged nymph to adult; one blood meal per active stage (three-host cycle). Molting requires the blood meal.

Reproduction

Females take one large blood meal, drop off, and lay a single massive egg batch (thousands) in leaf litter. Males may mate on or off the host.

Distribution

Global: Eastern North America
Native range: Eastern North America
Ontario: Established in expanding zones across southern, eastern, and parts of northern Ontario; range tracked by public-health surveillance and moving northward with climate

Ecology

Three-host questing tick. Larvae and nymphs feed on rodents and birds (the reservoir hosts for Borrelia); adults feed on deer (reproductive hosts, not reservoirs). Habitat: deciduous woodland edges, tall grass, leaf litter, not lawns or homes.

Resistance

Some acaricide tolerance reported in U.S. populations; Ontario status under surveillance. Not a crisis, but monitor.

IPM implications

Monitoring: drag-sampling and public tick submissions map risk; personal tick checks are the primary intervention. Landscape IPM is habitat-based, leaf-litter removal, wood-chip barriers, deer exclusion, not broadcast chemistry. Area acaricide application is a licensed-operator activity with strict limits near water and pollinators. Client education (proper tick removal, 24-36h attachment threshold for Lyme transmission) is the highest-value service.

Chemical ecology

Saliva is a pharmacological cocktail, anticoagulants, immunosuppressants, and cement proteins that anchor the mouthparts. Salivary proteins are vaccine targets. Pheromones coordinate aggregation on hosts (assembly pheromones on vegetation).

Genetics and DNA

Genome published (Ixodes scapularis), vector biology model for Lyme disease.

Taxonomy

Order Ixodida, family Ixodidae (hard ticks). Authority Say, 1821. Formerly Ixodes dammini, synonymized with scapularis; the Lyme vector of eastern North America.

Open questions

How fast range expansion will proceed under warming; evolving pathogen prevalence in new Ontario populations.

References

Sonenshine, D.E. & Roe, R.M. (2014). Biology of Ticks, 2nd ed., Oxford University Press.
Krantz, G.W. & Walter, D.E. (2009). A Manual of Acarology, 3rd ed., Texas Tech University Press.
CDC, Tick information (cdc.gov/ticks).