Knowing what ticks look like — and how small they can be — is the first step in protecting your family. Part of our Ultimate Tick Control Guide for Ontario Homeowners.
The Three Ticks Ontario Homeowners Need to Know
1. Blacklegged Tick (Deer Tick) — Ixodes scapularis
Why it matters: The primary carrier of Lyme disease in Ontario. Population is established and expanding across Southern Ontario.
Identification:
- Nymph: ~1–1.5 mm (poppy seed size). Translucent to light brown. 8 legs. Almost impossible to spot without magnification.
- Adult female: ~3–4 mm unfed. Reddish-orange body with a black scutum (dorsal shield) and dark legs. After feeding: up to 10 mm, dark blue-grey.
- Adult male: ~2–3 mm. Uniformly dark brown. Males feed less and are less commonly found attached to humans.
2. American Dog Tick — Dermacentor variabilis
Why it matters: Does not transmit Lyme disease, but can transmit Rocky Mountain Spotted Fever (rare in Ontario) and cause tick paralysis. Commonly found across GTA.
Identification:
- Larger than blacklegged tick: females ~5 mm unfed, males ~3–4 mm
- Brown with distinctive white/cream mottled markings on the scutum (females) or across entire back (males)
- More likely to be found in open, grassy areas rather than wooded edges
3. Lone Star Tick — Amblyomma americanum
Why it matters: An emerging species in southwestern Ontario associated with warming temperatures. Can cause alpha-gal syndrome (red meat allergy).
Identification:
- Medium-sized, reddish-brown
- Adult females have a distinctive single white or silver spot (the "lone star") in the centre of the back
- Currently rare in the GTA; more common in southwestern Ontario
Size Comparison: Why Nymphs Are So Dangerous
Blacklegged Tick Size Reference
Where Ticks Are Found in Ontario Yards
Knowing where to look is as important as knowing what to look for. Ticks concentrate at specific microhabitats:
- Lawn/forest edge: The single most important zone — ticks quest (wait for hosts) on vegetation at the transition between maintained lawn and any naturalized area
- Leaf litter and mulch beds: Ticks overwinter in leaf litter and emerge from these sites in spring
- Woodpiles: Mice that carry Lyme disease live near woodpiles, and ticks cluster around these areas
- Under decks and porches: Dark, humid zones that ticks use when conditions are dry or hot
- Dense shrubs and ground cover: Ticks rest in humid vegetation between questing periods
Frequently Asked Questions
How small is a deer tick nymph?
A blacklegged tick nymph is approximately 1–1.5 mm — roughly the size of a poppy seed. They are extremely difficult to spot on skin, hair, or clothing, which is why they are responsible for the majority of Lyme disease transmissions in Ontario. Adults are larger (3–5 mm) and somewhat easier to detect.
What does a blacklegged tick look like compared to a dog tick?
The blacklegged tick (deer tick) is smaller and has a distinctive reddish-orange body with black legs and a black scutum (shield) behind the head on females. The American dog tick is larger, with a mottled brown/cream pattern. After feeding, both species become significantly larger and more round — an engorged blacklegged tick can reach the size of a raisin.
Can I tell if a tick is carrying Lyme disease by looking at it?
No. You cannot determine whether a tick is infected with Lyme disease or other pathogens by visual inspection alone. If you're concerned about a tick bite, contact your healthcare provider. Some provinces offer tick testing services; check with your local public health unit.