Wednesday, October 24, 2012

Eco-Diary: Day 18

Here's what the creek looked like on September 17:



But I spent most of today looking at the orb-weaving spider that has made it's web in between the bars of the bridge railing:  


Ever since I wrote an article about spiders for WILD magazine earlier this year, I've thought they were pretty cool. There are 42,000 known species of spider on the planet, but scientists estimate there are at least twice as many more still undiscovered!

At first I thought this was Araneus diadematus, a European garden spider, but now I'm fairly certain it's Larinioides sclopetarius, a bridge spider. I can't find anything to confirm this, but I'm guessing that garden spiders are native to Europe and were brought over by colonists. The bridge spider is a holarctic species (found across the northern reaches of the globe), so one would expect it to be more common. Oh, and it's on a bridge.  

Orb-weaving spiders are a large family, with more than 3000 species worldwide, but only about 60 in Canada. They spin their webs by first constructing the anchor lines (like the spokes of a wheel) out of non-sticky silk that they can walk on. Then they create the spiral out of sticky silk to trap their prey.

You can see the spider actually letting out the silk and spinning its web in the next few photos. I watched it rebuild about two thirds of its web, working in a spiral around and around. It's pretty impressive how quickly it can do this. 





Just as I was leaving, I saw this little red squirrel (Tamiasciurus hudsonicus):

I also decided to start taking photos of the rocks along the southern shore of the creek, as a way of tracking changes in water levels: 

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