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Ever Wonder About Spider Webs?

On lazy hazy summer days, I keep walking into spider webs while walking my dog. I try to convert annoyances into sources of wonder, so I checked out the web to learn about webs.

Identification

At first, I had a trouble figuring out what these friendly neighbourhood spiders were, because the front legs seemed short. Then I realized they were just holding them in close. After browsing enough pictures of "spiders in bc", I decided, perhaps not too rigorously, that it was probably Araneus diadematus, also known as the Cross Orbweaver, the Diadem spider, or the European garden spider. The “cross" refers to the pattern of white dots on its abdomen, although this pattern is not always obvious. Diadem, is a kind of crown, as you might know from Harry Potter, and probably refers to this same pattern. As the “European" reference indicates, this is yet another organism introduced from someplace else. It now occurs in many places throughout the US and southern Canada, though not much in the great plains. They need habitats with enough attachment sites for webs. 

Life History

These spiderlings emerge from an egg sac in the spring and may take one summer or two to mature. They start out on a communal web and then make their own little ones. The conspicuous webs I’ve been walking into were probably made by females. The males stop making webs when they mature and then spend most of their time looking for a female to mate with. Females get to be up to 20 mm, while males only reach 13 mm. You’d think the males wouldn’t be so keen, given that they could get eaten by the larger female, but that’s nature for you.

Web Mastery

Charlotte of Charlotte's Web was based on a different species of the same genus Araneus. So let’s imagine a cousin of hers—Emily, say, is making a web. It will take about an hour, and Emily will repeat this particular process pretty much every day. Members of A. diadematus have even been in space to test their web making abilities, though the results were difficult to unravel and unfortunately the spidernauts did not survive the voyage.

Emily begins by eating her old web, though if the frame is still in good shape she may leave it. She usually starts a new one at night, although I have seen some working on them in the morning. Emily uses three pairs of spinnerets on the underside of her abdomen to secrete different kinds of silk, from rigid to stretchy. She starts off by making a bridge line with rigid silk from some point of attachment on a tree, bush, or lamppost, which can end up 2 metres long. She crawls over to the next attachment and builds up the frame of the web with guy lines. She adds about 30 to 35 spokes to the web. Next comes a non sticky spiral she adds from the outside in. After that, she makes an inner spiral with stretchy silk and sticky drops, all the better for catching insects with. She usually sits head down at the hub of the web, waiting for dinner to arrive. This seems rather vulnerable to me. When I blew on some spiders, some would shake up and down. This is supposed to make them look bigger as a defense mechanism, though I'm not sure how effective it is. Some hide in a retreat with a signal thread that tells them if something gets caught. When Emily does catch a tasty morsel, she'll wrap it in silk before eating it and might even save it for later. 

Now get out there and do some real web surfing in our Search: Sara Stern Gallery. We'll introduce you to Ruby, the red-kneed tarantula! Read more about the wonders of spiders, in Web of Intrigue (and Science), our article on spider webs and electrical charges.