Dock spiders (fishing spiders) are Canada's largest native spiders. While harmless, their massive size makes them a terrifying sight on docks, boathouses, and decks. Learn how to manage shoreline populations effectively.
Dock spiders (belonging to the genus Dolomedes) are fishing spiders adapted to semi-aquatic habitats. With leg spans reaching up to 9cm (3.5 inches), they are frequently mistaken for venomous exotic species, but they are native to Ontario's lakes, rivers, and cottage country. They don't spin prey-catching webs; instead, they sit near the water's edge and detect vibrations on the water surface to hunt insects, minnows, and tadpoles.
Their large size and dark grey-brown bandings make them highly visible, causing immediate panic despite being non-venomous to humans.
Docks, boathouses, underside of decks, and boat hulls provide the damp, dark shelter they need during the day.
They are nocturnal hunters that run across water surfaces. They only bite humans if trapped, sat on, or squeezed.
Total eradication of dock spiders is impossible because waterfront ecosystems are their natural habitat. However, you can significantly reduce their presence around your living areas by removing their shelter and food sources.
Waterfront pest control requires specialized care to protect delicate lake ecosystems. Spider Squad provides targeted, legal, and environmentally responsible treatments.
We apply microencapsulated barrier treatments to boathouse walls, cottage foundations, under-deck framing, and storage sheds. We strictly adhere to Health Canada guidelines, ensuring zero direct application to the water while protecting your structures.
Our technicians use extendable poles to sweep away existing spiders, webs, and egg sacs from boat hoists, dock frames, and eaves. Eliminating the egg sacs prevents hundreds of new spiderlings from hatching next to your lounge chairs.
Are Ontario dock spiders poisonous?
No. Dock spiders possess venom used to paralyze small prey, but it is not dangerous to humans. A bite might cause mild swelling and redness similar to a bee sting, but they only bite if directly handled or squeezed.
How big do dock spiders get?
A mature female dock spider can have a body length of 2.5cm and a total leg span of up to 9cm (3.5 inches), making them Canada's largest native spider species.
Can you spray for spiders near water?
Yes, but it must be done legally and carefully. Pest control products cannot be sprayed directly into the water. Licensed Spider Squad technicians apply treatments specifically to dry structural surfaces (decks, boathouse walls, foundations) in accordance with Ontario pesticide regulations.
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