February 7th, 2007
close encounters with Dolomedes spiders
(click on image for larger view)
Winter is begin to wear on me a little, and despite recent adventures such as the Mudpuppy Night, I’m beginning to long for my daily invertebrate safaris here at the farm. To remind myself of all the fun I’m missing, I decided to dig up some of photos and write about a few close encounters with Dolomedes spiders – the genus commonly referred to as the fishing spiders.
My earliest recollection of a fishing spider encounter occurred at my family’s cottage when I was about 6 or 7 years old. I was just drifting off to sleep on one of those rickety, old hide-a-beds in the living room, when something plopped itself down onto my eyelid. I lay very still for a few moments, my uncovered eye staring up into the darkness, as I tried to fathom what this thing might be. Then it began to move about my face — a sensation that I would liken to being gently brushed with eyelashes or a feather. I froze for another moment while carefully planning my next move, then whisked “the thing” off with my hand and bolted across the room to the light switch. I was just quick enough to catch a glimpse of an immense, dark, hairy-looking spider skittering into the crack between the mattress and the back of the sofa. I was not amused. However, there was no place else to sleep, so I turned my sleeping bag around, placed my pillow at the foot of the bed, and undoubtedly spent the remainder of the night brushing away imaginary spiders.
Fastforward almost half a century. In that span of years, many fishing spiders have come and gone. These days, the sight of a nice, fat, velvety, Dark Fishing Spider (Dolomedes tenebrosus) such as the one above, is always cause for great delight (click on all photos for larger views). Despite its common name, this species is often found wandering and hunting for prey far from water. In fact, most times, I find them resting atop a fallen log, or a cedar fence rail along the trailside. Sometimes, I’ll find one on the wooden dock at a local creek where I launch my canoe. They’re frequent visitors to cottages, a fact attested to by the number of times someone has emailed me a photo of the “gigantic spider” found under the sink or in the outhouse at a cottage.
So, why do we refer to the Dolomedes as “fishing spiders”? As the name suggests, this genus of spiders is usually found on or near water, “fishing” for aquatic prey, or other creatures attracted to the water’s edge. Typical prey might include water striders, small minnows and even tadpoles. Spiders such as the Striped Fishing Spider (Dolomedes scriptus) may be found clinging to a rock, piece of wood, or vegetation, with several legs resting lightly on the water’s surface as in the above photo. They wait patiently, sensing the approach of prey through the movement of the water. When something comes within striking distance, they make their move, seizing their prey, and even diving below the water’s surface in pursuit.
A frequently seen species is the Six-spotted Fishing Spider (Dolomedes triton) that may be found floating on the surface of ponds and streams. I often find them floating or gliding about on shallow, vernal pools and in ditches along forest trails.
The Striped Fishing Spider (Dolomedes scriptus) (above) is another freqently seen species. We’ve occasionally found them while paddling our canoe along the shorelines of creeks where they were resting on exposed tree roots or rocks. They are quite beautiful, having a white stripe running along the sides of the carapace and abdomen. The above spider was found resting on a log near Charleston Lake, just a few centimeters from a Dolomedes tenebrosus. Perhaps they were checking each other out.
Dolomedes spiders belong the to Family Pisauridae, commonly known as the Nursery Web spiders. They are referred to as such because the females construct a spherical egg sac and carry it in their jaws (chelicerae) until close to the spiderlings’ time of hatching. Then, they place the sac inside of a nursery web of silk strands secured to vegetation, and remain on guard close by. After hatching, the young spiderlings remain in the nursery for a time, occasionally moving away from each other, but quickly reforming into a ball when disturbed. I photographed the above ball of spiderlings on July 6, 2004, while doing a stream survey on the Jock River, west of Ottawa. I’m quite certain they are some species of Dolomedes, although I didn’t see the female.
While I watched over the spiderlings for the space of a few minutes, they would occasionally move apart. However, if a cloud passed over the sun, or my shadow fell over them, the spiderlings would immediately reform into a tight ball. I’m not sure if they move apart and back together in response to the slight changes in temperature when the sun is directly on them or in shadow, or whether they are using shadows as a cue that there may be danger close by, and regrouping as a defensive measure.
(click on image for larger view)
A final story to wrap up this piece on encounters with Dolomedes spiders. The above spider was photographed along the Cataraqui Trail near Opinicon Lake, on August 12, 2004. A friend, Eric Snyder, and I had been wandering along the trail, turning the odd stone or bit of wood to search for interesting invertebrates. One or the other of us spotted this spider under a small piece of cedar (see above and photo at top of this post). I’m quite sure it was a Dolomedes tenebrosus. It had just recently molted and was quite a bright orangeish colour. The exuviae lay crumpled in a depression in the sand beneath one end of the stick. When I attempted move in with the camera to shoot a few macros, the spider retreated to the exuviae. When I withdrew, the spider would abandon the exuviae, but quickly return to it when I moved in once more. I found that quite interesting and just a little reminiscent of the behaviour of the spiderlings in the little spider ball. Perhaps there’s some sense of safety in numbers, even if the “other” spider is just your own exoskeleton.
Tags: Dolomedes spiders, Dolomedes tenebrosus, Dolomedes scriptus, Dolomedes triton, Pisauridae
February 7th, 2007 at 6:46 pm
Very nice pictures. I especially like the striped fishing spider. Although the body doesn’t look much like the background, the legs almost disappear.
February 7th, 2007 at 6:47 pm
Nice piece on Dolomedes! I imagine your bedtime story has installed in many of your readers quite a few nights’ worth of nightmares!
They are spectacular spiders. I don’t think I’ve ever seen one on the water – usually they’re clinging to a vertical wall.
February 7th, 2007 at 6:54 pm
Mark – Thanks! I like the Striped Fishing spider too. It was actually the white parts that gave it away, and then I noticed the Dark Fishing spider nearby. I find that I see them more by shape recognition than by colour. After you’ve found quite a few, you just seem to notice them, even when they’re well camouflaged.
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Wayne – Ha! I debated with myself over posting that little story in case it initiated any new cases of arachnophobia! (-:
Yes, indeed, they are spectacular spiders. I see the Dark Fishing Spiders away from water most times, but the Six-spotted always on water. The Striped usually at or near the water’s edge.
February 7th, 2007 at 8:44 pm
Great post!
“After hatching, the young spiderlings remain in the nursery for a time, occasionally moving away from each other, but quickly reforming into a ball when disturbed. “
Interesting. Some spiderlings we saw last summer did exactly the opposite: scatter when we moved too close.
There’s a photo, of sorts (film camera, hardly any zoom) on my old blog, here.
You’ll have to click on it to get any sort of view; Delphi only allowed those tiny thumbnails.
February 7th, 2007 at 9:18 pm
I was checking out the Living the Scientific Life blog and saw a spider picture. For a moment I thought I had accidentally loaded Burning Silo, and then I saw that it was, indeed, your spidey picture. I knew I recognized it.
Oh, your spider story reminds me of my scorpion stories. There’s the one where a scorpion dropped from a beam in the living room ceiling directly between my bare legs, and the one where I rolled over onto a scorpion in bed. I checked my bed carefully for years after that one.
February 7th, 2007 at 9:50 pm
Susannah – Thanks! That’s interesting about the spiders dispersing when approached. Now I’m wondering if these were just regrouping because they noticed the temperature change when there was a shadow passing over them. Hmmm. Now I’ll have to find more spiderling balls to study and conduct some experiments! Interesting stuff though, isn’t it?
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Mark – Thanks for mentioning that, Mark. I had sent quite a few photos of different creatures to GrrlScientist awhile back and the spider is probably the last of them to appear on her blog. I must round up some more to send along.
I think that if scorpions fell off of ceilings or I found them in my bed, I’d be checking for them pretty often too! (-:
February 7th, 2007 at 10:49 pm
HI! Those are great spider pictures!!! Made them look pretty. I wonder if there are fishing spiders where I am–I’ll have to check it out(we don’t seem to have many spectacular spiders here–although the webs are pretty). Thanks for all the work in putting that together.
February 8th, 2007 at 1:37 am
Celeste – Thanks! I just did a quick check to see if I could find out if Dolomedes spiders are found in the PNW. I didn’t find anything that said that they were for sure, but I’d be kind of surprised if there weren’t at least a couple of species out there. I did see a note from someone posted to a message board saying they had seen Dolomedes triton in eastern Oregon. Thanks for dropping by and leaving a message. I found my way over to your blog and I’ll be back to read more.
February 8th, 2007 at 2:31 am
Wonderful photos and posts about a group of spiders i knew nothing about. Thanks! One minor quibble, though: shouldn’t the singular form be exuvia?
February 8th, 2007 at 2:43 am
Dave – Thanks. For years, I didn’t know much about them other than that they were big. (-:
Exuviae is one of those words that is the same in both singular and plural (or at least, that’s what my dictionary says). I’m not exactly sure why that would be, but that’s how it usually appears in spider and odonate field guides. Maybe someone reading this will know what rule makes it so.
February 8th, 2007 at 6:25 am
Bev, keep posting these incredibly informative bits…even for those of us who are, as of now, totally lost with respect to the true science of your observations, they are wonderfully informative.
February 8th, 2007 at 7:17 am
Great post Bev, thanks.
February 8th, 2007 at 2:31 pm
John – I’ll probably keep on posting them so long as there is someone reading them. (-:
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Duncan – Thanks!
February 8th, 2007 at 3:23 pm
I’m so glad you searched your archives for these spider pics. They are so beautiful, and the accompanying text incredibly informative. Roger and I have had the same response from the Argiope aurentica spiderlings that Susannah has. They disperse when we come upon them in their nursery.
Looking at these pics is almost as good as being outside!
February 9th, 2007 at 11:58 am
Great pictures! I’m wondering if I’ve seen these and thought they were wolf spiders. We recently moved to a home on the edge of a wetland, so I’m hoping that I’ll find some around this summer now that I know what to look for.
February 9th, 2007 at 12:15 pm
robin – At this time of the year, it sure lifts the spirits to look through summer photos. I’ll probably post more like these spider photos very soon. Interesting about the Argiope spiderlings dispersing. Having read what you and Susannah have written, I’m guessing that the spiderlings I watched must have been reacting to shadows and temperature change, and perhaps not perceived the shadows as a threat. Perhaps they would have dispersed if they had thought so. Interesting!
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WW – Thanks! It could be that you’ve seen these spiders and thought they were Wolf Spiders. They are enough alike that they are easily confused. There is a difference in their eye arrangement, but that’s really very difficult to see without some kind of magnifying glass. Also, Fishing spiders tend to rest with their legs really splayed out, but I rarely see a Wolf spider do that — they usually seem ready to move at any second. If you’re close to a wetland, I’d look for Dolomedes triton around vegetation at the shallow edges, and also be checking any fallen trees, rotting wood, etc.. for spiders. I’m guessing that you’ll find some there for sure.
February 11th, 2007 at 12:16 am
A number of online sites do give exuvia, though, including the Free Dictionary.
May 26th, 2007 at 9:26 am
First picture with this text: recently molted Dolomedes spider with exuviae in background (Aug. 12, 2004)
This is absolutely not Dolomedes, not even a Pisauridae, it’s a wolf spider family Lysosidae.
May 26th, 2007 at 2:01 pm
Hi Filip – do you think so? It was absolutely huge for any wolf spider species I’ve seen here in eastern Ontario, and I have seen many wolf spiders over the years. This was probably double the size of any species I can think of. Definitely more in the size of a very large Fishing Spider.