Facts about dock spiders

11 June 2014 Around The Property

dock spider (fishing spider) with egg sac

Amazing dock spider or fishing spider facts

Dock spiders are very common around cottages, cabins, and lake houses in Canada and the United States. Many people fear them, but these spiders are actually fascinating creatures.

The scientific name for a dock spider is Dolomedes. It belongs to the Pisauridae family of spiders. In Canada, this spider is usually referred to as a dock spider. In the United States it is often called a fishing spider. Other common names include wharf spider and raft spider.

Infographic: Dock Spider Facts

Infographic: Dock spider (fishing spider) facts

Dock spider habitat and range

Dock spiders are widely distributed throughout cottage country in Canada and the United States. Whether your cabin is in Michigan, Wisconsin, Minnesota, Manitoba, Ontario, Quebec or any other lake-country area the dock spider is a regular and feared companion at the cottage.

Big female fishing spiders tend to be the ones we see most often on the dock. This is their prime territory for hunting aquatic insects, minnows, tadpoles or any other meal that happens to float or swim by the spider’s hiding place.

Big Dock Spider

Smaller dock spiders are often found around the cabin, outdoor shower, sheds, or even in the outhouse and will feed on a variety of insects and bugs.

This one caught a daddy-long-legs on the cottage deck.

dock spider (fishing spider) attacks daddy-long-legs spider

Are the spider bites fatal?

Like most spiders, dock spiders use venom to paralyze their victims. Fortunately, they have little interest in people. Dock spiders are generally not aggressive regarding humans and will usually hide when we approach. A dock spider will only bite a person in the rare situation that the spider feels threatened, for instance if the female spider is protecting its young.

Unless you grab the spider or inadvertently step on it, you will likely never be bitten.

A dock spider has large enough fangs to break the skin, but a bite is not dangerous to humans unless the person has an allergic reaction to the bite.

This large dock spider preferred the comfort of living inside the cabin.

dock spider inside the cabin

How big do dock spiders grow?

Dock spiders are Canada’s largest spiders. A female dock spider can grow to be more than 3.5 inches or roughly nine centimetres.

The one shown above was photographed sitting on a shirt about three feet from the bed in the cottage.

How well do these spiders swim?

A dock spider can actually swim under water and stay submerged for several minutes. It uses air bubbles trapped in the fine hairs on its body under its belly to provide oxygen while it is under water. Essentially, the spider performs a type of scuba dive.

Dock spiders can walk on water

Dock spiders seem to defy gravity and will walk along the surface of the water. They can do this because their feet do not get wet and their weight is distributed in a way that the surface tension of the water is not broken.

Dock spider egg sac size and number of babies

A female dock spider will carry the large egg sac in its mouth using the fangs or with its pedipalps or front legs until the young spiders are ready to hatch. The female spider chooses a safe place for the egg sac and surrounds it with a protective web. The mother spider then stands guard until the baby dock spiders hatch.

Fishing spider (dock spider) carrying huge egg sac.

Each egg sac contains hundreds of baby dock spiders. It is an unnerving sight when we discover them just after they have hatched. This is especially the case when the mother spider has decided to hide the egg sac somewhere in the boat.

Read a horrifying dock spider story about what happened when our editor accidentally stuck his hand into a dock spider’s nursery web.

Written and photographed by Andrew Walker