May 25th, 2006
windblown world - part two
Yesterday, I wrote about how dragonflies battled high winds by sheltering inside of the many small Beech saplings that grow along the trail on the north side of Murphys Point on Big Rideau Lake. In part two of this account, we’ve moved away from the lake and are now in a forest opening — a tiny damp meadow sheltered by low rocky ridges. This little clearing is typical of countless like it that are found when hiking up on the Canadian Shield. The soil is thin and often damp in spring as water is trapped on the surface by the underlying rock. The air is often warm as the surrounding ridges act as a windbreak, but also as a heat-sink, absorbing and holding the heat of the spring sunshine. By midsummer, the granite ridges often feel oppressive to traverse on a hot day, and these small meadows usually dry out — the mosses becoming crisp, and the grasses bleached bone dry.
In just such a meadow, we spent several minutes observing dragonflies. More than a dozen Chalk-fronted Corporal (Libellula julia) bobbed and darted close to the ground as they hunted for mosquitoes and other small insects. I caught a glimpse of a small sliver of metallic green and soon found my first Six-spotted Tiger Beetle (Cicindela sexguttata) of the season, stalking prey from various vantage points. We found several American Emerald (Cordulia shurtleffi) dragonflies basking on the leaf mulch (see photo below - click on images to see larger versions). This species of Emerald is recognized by its flaring black abdomen, and the metallic bronze ring at the narrow point between the thorax and abdomen. Eyes of the mature adult are a vivid green.
With so much flying going on all around us, it’s probably not that surprising that we weren’t paying much attention to events on the ground… that is, until Don noticed two large Wolf Spiders (Lycosidae) carrying gargantuan egg cases (see top photo). By the time I finished up shooting photos of the Emerald dragonfly, he had discovered many more Wolf Spiders — all carrying egg cases — emerging from within a low, very dense Vaccinium bush of some sort. As near as we can figure out, Don must have slightly disturbed the bush with his toe, sending spiders off in all directions over the leaf mulch. There were so many that we couldn’t really keep track of them, but it probably wouldn’t be exaggerating to say that there were about two dozen or more - all of the same species (as yet unidentified) - and all carrying egg cases. I’ve never seen or heard of such a strange aggregation of Wolf Spiders, and in fact, we both found the whole event rather astonishing.
I’ve posted some notes about this incident to the Nearctic Arachnologist’s Forum, so perhaps I’ll get some feedback about this sighting. If so, I’ll post a follow-up. My only explanation for the aggregation is that the weather of the previous couple of days had been cool and rainy. Perhaps the very dense little bush had provided an ideal spot for the spiders to seek shelter. However, that said, I find it very odd that the spiders all appeared to be of the same species, and all of them with egg cases — seeming to indicate that these spiders must have been hanging about a very restricted area near the bush before the rains. That in itself seems rather odd. In the past, I’ve noticed that a few Argiope orb-weaving spiders persist in attaching their egg cases to a particular couple of spruce trees in a long row of near-identical trees that border the meadow that I refer to as Spider Ranch here at our farm. I’ve always wondered if there might be a sort of “return to the place where it was spawned” instinct among some creatures such as these spiders - something akin to the instinct that drives salmon to return to a certain section of river. Do some spiders have a similar instinct to return to a certain site when it comes time to make an egg case or when eggs are about to hatch? It seems almost impossible, and yet, who knows?
Tags: American Emerald, Cordulia shurtleffi, Chalk-fronted Corporal, Libellula julia, Six-spotted Tiger Beetle, Cicindela sexguttata, Wolf Spider, Lycosidae
May 25th, 2006 at 5:45 pm
It would be so interesting to know if this wolf-spider behavior is an anomaly. I have never seen a a group of spiders together with their egg cases. That seems so unusual. I always think of spiders as being rather solitary. Do you know of other spiders that live in any type of community? I am woefully ignorant about insects. Stunning close-ups. Especially that wolf spider. Really beautiful.
May 25th, 2006 at 9:35 pm
RA - So far, I’ve received a couple of replies from the Canadian Arachnologist’s Forum. One person (from Uruguay) said he hadn’t seen anything like that before (he studies wolf spiders). However, I received another reply from someone in Colorado, and he says he’s noticed that certain species seem to gather in large numbers under certain conditions — some species are attracted to water sources, etc… He also mentioned that, at times, when they’ve been doing research, they’ll find a lot of either male of female of certain species, but not both together. He thinks my theory of an aggregation caused by weather conditions might not be too far out. Anyhow, fascinating event, and also quite interesting to hear what some arachnologists have to say about it.
May 26th, 2006 at 1:18 am
Love the picture of the wolf spider. It sounds pretty interesting that so many had congragated in one small location. When I was a teenager living in a basement bedroom, quite often I would have 3 to 5 wolf spiders living within about a square meter in the corner of my room, usualy lower to the floor. Not exactly natural habitat, but as a teenager, my room was pretty wild ;)
Could you post a link to the Arachnologist’s forum? A quick couple of google searches didn’t turn it up easily.
May 26th, 2006 at 1:37 am
Your photos are great…the wolf spider is awesome. I have never heard of wolf spiders gathering in one palce before. I did have a very large one fall from a tree and land in the canoe one time…and my son jumped out. It was really funny.
May 26th, 2006 at 2:14 am
Hi Peter - Here’s the URL of the Nearctic Arachnologist’s Forum.
http://canadianarachnology.dyndns.org/forum/
Jimmy - Thanks! Yes, some people are quite nervous of spiders. But then, many are don’t really like snakes too much either. I always wonder exactly what it is about some creatures that make people dislike them.
May 26th, 2006 at 9:57 am
The photo of the wolf spider is great. The grouping behavior is certainly interesting. Ours aren’t quite as thick as yours but the comparable ones are quite large. Their egg cases are a very pale blue.
I enjoy working in the garden with the wolf spiders around, but I have been bitten by one when I apparently grabbed it along with some weeds. It was basically a hard pinch that didn’t break the skin, but I can now claim to have been bitten, however under duress the provocation was.
The emerald dragonfly eyes are amazing! I’ll have to be looking for some of these now.
Also - nice tiger beetle pic! I see it has the two small dorsal spots in addition to the six peripheral ones.
May 26th, 2006 at 10:46 am
Oh, btw, regarding your meadow. North Georgia also sits on a granite bed and although much of it is covered with sediments washed down from the Appalachians there are places like yours where it pokes through. There’s one such granite outcrop area covering several acres within the Athens city limits. It’s protected and cared for by the neighborhood association around it. In the spring, when it rains there are dozens of tiny streams that run through the outcrop keeping the soil thin. That’s when huge numbers of sandworts and other xerophytes flower, and then in the summer it is as you say parched and dry with only the hardiest of lichens and mosses and a few aster types in deeper soil showing much sign of life. It’s an amazing place.
May 26th, 2006 at 12:15 pm
Wayne - I expect I may have been bitten by wolf spiders when working in the garden — under the same circumstances. However, most of the time, the only thing they want to do is run away as fast as they can.
And yes, aren’t those granite outcrops and ridges quite fascinating. Up here, we get Wild Columbine growing in the tiniest pockets or cracks in the granite and flowering in spring. In summer, the delicate Corydalis bloom where it seems nothing else could survive the heat and dryness.
May 26th, 2006 at 12:56 pm
I really should do a larger post on our own granite outcrop here. There’s larger ones around (Stone Mountain east of Atlanta is one) but this one is exquisite. I’ve taken students out there on field trips every summer and it’s like nothing they’ve seen.
I did do a smaller post awhile back, but can’t offer it to you as a link since I can’t get to my site :-) . If you can see the site a search on “granite” or “outcrop” would get you to that post.
I find it a lot of fun to be watering an area and watch the wolf spiders all run out.
May 26th, 2006 at 1:06 pm
I found this site through the Niches links and am glad I did. The photos blow me away and give some inspiration, along with Wayne’s, to do more photography. All I need to do is win the lottery so I won’t have to work so much.
May 26th, 2006 at 2:19 pm
Wayne - I just found the post from Feb. 16, 2005. Yes, that sounds very similar. As you have mentioned the ecology is very unique due to the heat tolerance of the plants and their ability to persist in a place with so little soil. I often think that people don’t really pay enough attention to those kinds of habitats because the scale of the plants tends to be very small - limestone alvars are a similar case. Not flashy, but very interesting.
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Mark - Glad to see that you found your way over here from Niches. Thanks re; the photos. And yes, definitely get to work on the photography. It’s such a wonderful way to learn about and share knowledge about nature.
July 11th, 2006 at 2:46 am
Bev, being my first post on your site, let me just say how wonderful and educational your blog is, and let’s not forget your outstanding photos too - I’ve bookmarked your sites at my Pbase page on spiders.
Long ago, I posted a thread on www.dpreview.com (being an owner of a Nikon Coolpix 4500) titled “Constipated Spider”. I didn’t know better at that time, but the spider that was running around in my bathroom sink and unable to escape was actually a wolf spider with an egg sac. A gentleman left a comment underneath my picture, and that’s how I knew :> http://www.pbase.com/dlcmh/image/17355923/original
July 11th, 2006 at 11:16 am
David - Glad you found your way to my site and are enjoying reading the posts. That’s a beautiful photo of the spider in the Pbase gallery (along with the other spider shots!). Interesting interpretation of the egg sac on the spider. :-)