I just returned from a week of vacation on beautiful Stony Lake, north of Peterborough, Ontario. A lot of time was spent sitting on docks (Note: the correct terminology should be Wharf instead of dock i.e. you ‘dock’ at a wharf; however, it is generally more commonplace to use the terminology Dock), at water’s edge. Where there are docks wharfs, there are spiders. The most common species on the docks tends to be the (in)famous “dock spiders”. I am pretty sure that dock spiders are the largest spiders in Canada (if not, please correct me!). I receive many phone calls and e-mails about dock spiders, and I suspect an impressive amount of arachnophobia can be blamed on this hairy wonder of the Arachnid world.
Dock spider (Family Pisauridae), Dolomedes sp.
Dock spiders belong to the family Pisauridae, which are closely related to wolf spiders (family Lycosidae). Both of these families of spiders show interesting behaviours towards their young (‘spiderlings’). Females lay eggs within a silken egg sac, and this sac is carried around by the female until it is time for the young to hatch. Wolf spiders attach their egg sacs to the end of their abdomen, and when the spiderlings hatch they are carried around on the mother’s abdomen before embarking on a solitary life. Pisaurid females, however, hold the egg sacs by their fangs, and it is carried underneath the female’s body – it looks like the females are carrying around a big wad of cotton by their mouths. Pisaurids are commonly known as nursery-web spiders, as females build a silken, tent-like ‘nursery’ for their spiderlings. Upon hatching, the young spiders live in a protected place, typically spun in and among grasses, low-growing vegetation, or between rocks around the margins of water.
A dock spider (Family Pisauridae), Dolomedes sp., in its favourite habitat
Two species, Dolomedes tenebrosus and Dolomedes scriptus are the common ‘dock spiders’. Unfortunately it is difficult to tell these two species apart, without a microscope, forceps, and expertise. Both species are brownish-grey in colour, with black and light brown markings (‘chevrons’) on their abdomen. These spiders, especially the full-grown females, are the largest (native) spider species in Canada, and their body (including legs) can almost fill your palm – the body length (i.e., not including legs) of mature females can easily exceed 2 cm. But do not worry! These spiders do not bite people, and would rather eat land-dwelling and aquatic insects, and they are known to catch small minnows, which is the reason for their other common name, the fishing spider. The spider will wait with its front legs resting in the water, and when small tadpoles or fish come near, the vibrations alert the spider to its lunch. An invertebrate eating a vertebrate is not a common occurrence in the animal kingdom!
Dock spider habitat
Dock spiders, as their name suggests, tend to be associated with the margins of lakes, ponds, swamps and rivers, where they typically sit motionless on tree trunks, rocks, boats, and docks. However, individuals are known to travel some distance from water, and are the reason for many alarmed people describing hairy monsters in their basements. This mainly occurs in the autumn months when the spiders are searching for a warm place to spend the winter (under stones, leaves, or bark, or inside buildings). After spending a winter as an immature spider, dock spiders typically mature and mate in the spring, with females carrying egg sacs for a few weeks, before the young hatch in the nursery. Females can then go on to produce a second, or sometimes a third egg sac before the end of cottage season. One egg sac can produce over 1,000 spiderlings.
Without a doubt, dock spiders are impressive animals and although not small and obscure, they are still worthy of study. They should be considered friends of cottagers, boaters and home-owners. I encourage you to watch them, observe their behaviours, and marvel at their size – it’s especially fun to do this when sitting down at the dock, having a glass of your favourite beverage, watching when the evening comes….
I’ll make a deal with you – you sit on the edge of the dock watching the spiders, while I have a glass of my favourite beverage watching the tv.
Great photos, but one suggestion: When the size of the organism is important, it’s helpful to add something for scale, like a coin.
Thanks for the comments! I totally agree that something for scale in the photos would be most useful- however, these species tend to be rather skittish and I have yet to photograph one with something relevant for scale in the shot- but I will keep trying.
How big would it be, let’s say, relative to the sole of my shoe?
We saw an impressive Dolomedes at Elora Quarry last summer — obviously very well-fed. My husband described it as “an eight-legged crocodile.” They don’t allow adult beverages on the beach there, but I seem to recall that we toasted our spider buddy’s health with both ice water on-site and a glass of wine at home afterwards.
great story! Thanks for sharing. Glad you toasted the spider’s health – hope s(he) is still alive!
Chris, pay attention here. A “dock spider” is more properly termed a “wharf spider”. As my father instilled in us, a dock is where the boat parks, a wharf is the physical stucture which of course is the wharf spider’s preferred habitat. I fear I am fighting a losing battle.
Hilary
Hilary – you are SO correct, and I thought of you and your family when writing this post… unfortunately, “Dock spiders” is the (more-or-less) accepted common name despite Wharf being a more correct term…
OK – so I have now put some terminology about Wharfs instead of Docks into the first paragraph
A freind of mine showed me a picture of 1 of those dock spiders during an exercise at CFB Petawawa (in the Ottawa Valley). The spider was so big that it stretch from the wheel well to the bed cap (cover on the bed of a pickup truck) of a Chevy Silverado. The spider fits the descriptions that I have read so far, including the size. It amazes me that these amazing creatures exist in Ontario yet the schools don’t teach the kids about these things.
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We have a camp in Restoule, Ontario. We have huge “dock spiders”. This past summer we had them dropping down from the ceiling of our gazebow, onto the table. Man they are so big and scarry looking. We also have them in the out house. I just hate going out there and seeing them. They give me the creeps. Until this year I really hadn’t seen them dropping. We know they won’t hurt us but they are soooo big and hairy. We had one on the hearth with a sack of eggs. It was probably about 81/2 cm including it’s legs.
Ohhhhhhh!!!!!!!!!!!!!!! yuck.
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Who wrote this? We have a place on Stony and always encounter the wharf spider
Yes, I have spent a lot of time on Ston(e)y Lake, and see this species there, often!
i comented just now. but i need help with these spiders… there is so so many i live in some fear and lose lots of sleep!
so i have LOTS in my bacement apt.. what do i do? how do i handle them around my child and pet. I have seen them trying to attact my dog!
Well… you need not worry – spider bites are exceedingly rare! I’ve written about the topic here: http://arthropodecology.com/2012/02/15/spiders-do-not-bite/
Chris, I have now found dead ones in my bed after waking up in the morning! Im actully highly considering moving out of my apt. How do you suggest i get rid of them before they get rid of me ?!
Don’t worry, Ashley – they are not after you! There are lots of spiders in our houses, all the time – moving somewhere else will not solve the problem. If they bother you, vacuum them up regularly.
I was bitten by a dock spider and became extremely ill. Others have been bitten as well. Search dock spider bite.
Hello Suzanne- by in large, spiders bites are exceedingly rare. http://arthropodecology.com/2012/02/15/spiders-do-not-bite/
I am well aware of the many, many stories of spider bites out there on the internet. However, I would argue that in the vast majority of cases, actual spider bites (by any spider! including dock spiders) are uncommon. What is common is that people implicate spiders all the time, without real evidence that a spider actually bit them. It’s easy to blame the spider, but in many cases other, more likely causes are to blame.
I can also provide many anecdotes about spiders – in my case, I have handled hundreds (thousands?) of spiders over almost 20 years; I have studied them, collected them, reared them, and have never been bitten. I spend summers at cottages, on wharfs, in and near ponds, and have never been bitten by dock spiders. They run from humans.
I’m currently looking at two of them. One is a it larger than the other and the smaller one is darker…the other more grayish. Interesting looking creatures.
last nite we had company overnight at the cottage in Northern Ontario. My friend was sitting on the sofa when one of the largest wharf spiders I have ever seen crawled up behind her and disappeared. They give me the creeps and I want them out of my cabin!