June 13th, 2006
inside the nursery
Several months ago, I wrote about watchful spiders that guard their egg cases. On Sunday, while hiking at Murphys Point Provincial Park, I found another nice example of a maternal spider that constructs it nursery shelter in the upper leaves of Common Milkweed plants. As you can see in the above photo, the leaves are gathered together to form a chamber. You can just see the upper side of the spider’s abdomen through the little “window” in the chamber (click on image to see larger view).
Taking care not to damage the chambers, I peered inside a couple and shot a few photos. A dense network of spider silk fastens the leaves together with the spider and its egg case sheltered deeply within the structure. All of the chambers were occupied by the same species, the Nursery Web Spider (Pisaurina mira) — a large, two-toned brown spider which is known for the maternal guarding of its egg case. It will remain inside the chamber with its case until the young spiderlings have hatched out.
Above is a photo of a spider which seemed to have just begun the process of fastening the top leaves of a milkweed together with silk. I’m guessing that she is beginning to prepare a chamber similar to the others which I found. This species of spider is recognized by the dark brown band with wavy pale borders that runs across the top of the abdomen from front to back. As you can see from the photo, it’s quite a handsome and goodly-sized spider with very long legs.
EDIT: I’m moving an excerpt of this comment from a previous post on spiders up to a place where it will be seen by more readers of this blog. I urge anyone with more than as passing interest in spiders to check out The Canadian Arachnologist website, the Nearctic Spider Database, and the Nearctic Arachnologists’ Forum (all of which can be accessed from the main page). Here is a little bit of info about the database written by David Shorthouse who maintains the site:
If I may shamelessly plug the Nearctic Spider Database for folks like yourself with an interest in spiders, bear with me.
This has been a labour of love for the past ~year and content is really starting to develop. One of the goals I had at the very start was to accommodate casual observations that might not have ever reached print. These sorts of general natural history comments in my mind are just as important as published species descriptions. So, on this front, I just configured a “leave a comment” icon and link for each of the ~4,400 Nearctic spider species pages. Eventually, visitor comments will be integrated into the species page proper if these are of sufficient quality and reach a general consensus. I may eventually permit image uploads, but first I’d have to cluster the server and move it out of my basement ;)~ In the meantime, I welcome (as will many others like me) comments in the individual species pages.
Keep up the great work Bev!
David P. Shorthouse
Dep’t of Biological Sciences
University of Alberta
Edmonton, AB
Tags: Nursery Web Spider, Pisaurina mira, Common Milkweed, Murphys Point Provincial Park
June 13th, 2006 at 1:30 pm
I once found a the corpse of a spider guarding a white plastic ball that never hatched.
June 13th, 2006 at 1:44 pm
Monado — That’s a very interesting incident!
June 13th, 2006 at 3:13 pm
Those are quite handsome spiders. I love how they fasten the leaves together to create a safe chamber for their eggs. When the female is in there, protecting the eggs, how does she eat? Does she ever leave the chamber to search for food, or do other hapless insects wander by? Or do they simply not eat during this time? Excellent photographs, Bev.
June 13th, 2006 at 9:10 pm
Great Photographs…I am always learning something from you site….
June 13th, 2006 at 11:18 pm
RA – Thanks! Regarding the spider eating while protecting the egg case… I’m quite sure she doesn’t eat at all. I’ve watched other spiders guard their eggs over a period of time and they never seem to leave them. In one particular instance, I photographed a Goldenrod spider guarding her eggs within a sealed rose leaf. She remained on guard for almost 3 weeks as her body slowly shrank down to nothing. I know she could have hunted during that time, but she didn’t try. In fact, there was something even a little odd that went on while she was on guard and that was that a grasshopper used to sit on the same leaf nearby for hours each day. This went on for at least two weeks – probably even longer. I’m certain it was the same grasshopper as I photographed it often while photographing the spider and it looked the same in the photos. I have no idea why it stayed there, but it must have had some reason.
June 13th, 2006 at 11:19 pm
Jimmy – Thanks! I’m always learning something new too — pretty much every day! (-:
June 14th, 2006 at 12:05 am
Odd, that it would let the grasshopper sit there while it is supposed to be on guard. Maybe it was not perceived as a threat, or they only defend the eggs when they get attacked? I’m curious, about what actualy triggers the defensive response, and how they react when it’s triggered.
June 14th, 2006 at 2:21 am
Peter – I’m not sure why it seemed to ignore the grasshopper. I suppose it might have done something if the grasshopper had actually tried to get at the eggs. I don’t know that the spiders can actually do very much if they think the eggs are under attack. The first few times I photographed the goldenrod spider with its egg case, it would get on top of the leaf and grip onto it with its legs. I suppose that, in the case of this species of spider, it’s not accustomed to being challenged as they really are quite accomplished predators (I photographed a medium sized one with a fairly large dead bee fly this afternoon). What was interesting about the goldenrod spider is that, after I’d visited it to shoot photos a few days in a row, it began to ignore me and just sit on the leaf without moving to the sealed leaf containing the eggs. I guess it realized that I wasn’t going to bother the eggs.
June 14th, 2006 at 9:40 am
You posts are alway learning experiences. Thanks for this posting, the great conversations in the follow up, and the special spider link!