Canada's largest spider is a fearsome predator that grows to 9 cm and lives in Ontario
If you’re planning on taking a trip up north to Ontario’s cottage country this summer, there’s a good chance you’ll encounter a dock spider at some point or another, especially if you’re staying at a lakefront property or embarking on a boat day.
Dolomedes is a genus of large arachnids commonly known as fishing spiders, raft spiders, dock spiders, or wharf spiders. Nearly all Dolomedes species are semi-aquatic, including dock spiders, which are capable of walking on water thanks to their widely spaced legs and H2O-repelling hairs.
Female dock spiders can grow to be as large as an adult’s hand (up to 9 centimetres) and are about twice the size of a male spider.
As its name suggests, the species is most commonly found on docks, boats, boat houses, and even rocks during mating season. The terrifying-looking spiders can also be found near rivers, streams, ponds, marshes, and reservoirs.
Dock spiders are also sometimes referred to as fishing spiders due to their hunting behaviours. Unlike other species, dock spiders do not spin webs to catch prey. Instead, they dangle over water and rest their front legs on the water’s surface to feel for vibrations.
Photo: OliverGraphics.ca/Shutterstock.
Once they detect moving prey, which may include water insects, tadpoles, tiny fish, and minnows, the spiders run across the water’s surface to attack them and inject their venom.
Dock spiders can be distinguished by their two rows of eyes, brownish-grey colouring, eight legs, as well as black and brown markings on their abdomen.
While dock spiders are generally not aggressive toward humans and will run away when approached, they might deliver a bee-sting level bite to you if they feel threatened or startled, although these situations are extremely rare.
Most cases occur when dock spiders are forcibly head, sat on, stepped on, or trapped inside clothing.
Photo: valleyboi63/Shutterstock.
If you spot a dock spider, your best bet is to leave it alone and not attempt to remove it or detach an egg sac by hand, which will only increase your chances of getting bit.
If you’re keen on keeping the ferocious-looking spiders away from your property, make sure to remove piles of rock or wood debris around your home, shed, or boathouse, keep all shoreline plants trimmed to eliminate possible hideouts, and remove or minimize any standing water on your property.
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