Canadian Venomous Spider Identification Guide
Learn how to identify the Northern Black Widow, recognize standard harmless Ontario spiders, evaluate the health risks of a bite, and access emergency exterminator services.
The **Northern Black Widow** (*Latrodectus variolus*) is native to parts of Southern Ontario, particularly along the Lake Erie shoreline, sandy beach environments, and rocky wooded crevices. While encounters are rare, they do occur, especially in outdoor woodpiles, crawlspaces, dark sheds, and unused basement corners.
Black widows are highly venomous. Identifying them accurately and separating them from harmless house spiders is crucial for your safety and peace of mind.
| Feature | Northern Black Widow | Common House Spider | False Black Widow (Steatoda) |
|---|---|---|---|
| Color & Finish | Glossy, coal-black; smooth cuticle | Dull brown, grey, or tan; patterned | Slightly glossy dark purplish-brown |
| Markings | Split red hourglass on underside; red spots on back | Vague chevrons or speckles on abdomen | Crescent-shaped pale stripe on front |
| Web Type | Irregular, tangled, extremely strong sticky silk | Messy, loose, flimsy cobwebs in corners | Similar to widow but less dense/strong |
| Bite Danger | ⚠️ Medical Emergency (Neurotoxic venom) | ✅ Harmless (Minor local itch/redness) | Moderate (Slight local pain, swelling) |
A black widow bite is a serious medical event. The venom is neurotoxic and can cause severe muscle cramps, abdominal pain, nausea, sweating, and difficulty breathing (a condition known as latrodectism). While bites are rarely fatal when treated, immediate medical attention is always required.
Black widows are non-aggressive and typically bite only when squeezed or pressed against skin (such as when putting on gardening gloves or reaching into a dark woodpile). If you locate a glossy black spider with red markings or a dense, sticky web in your home, do not attempt to kill it yourself.
🚨 Warning: Do not attempt to catch or handle suspected black widows. Contact Spider Squad at 905-935-7498 for immediate professional extraction. Read more on our Ontario Black Widow Guide Page or read general bite symptoms on our Spider Bites Guide.
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