As mentioned in the previous post, many critters have been introduced to this area, and this ubiquitous spider, the cross orbweaver (Araneus diadematus) is one of them. This critter makes all the beautiful and/or annoying webs all over Seattle yards starting mid-summer and continuing through the autumn.
Introduced in the late 1800s, likely in shipping containers, these spiders have spread across the northern US and Canada and altered the ecosystems they inhabit. As mentioned earlier about the non-native species, this is another beauty that is hard to hate when you see how skilled they are at web-building. Many consider these spiders a positive addition to the landscape because they are presumed to reduce insect pests. Not that it matters now, with these spiders spread far and wide, but for those of us who don’t consider any insects pests, their benefits are not as obvious, and their potential harm to native ecosystems looms large.
You can clearly see the cross that has given these spiders their common name in the photo above.
These spiders breed and die as the weather chills, leaving egg sacs behind that hatch into hundreds of tiny yellow and black spiderlings the following spring. I often grab egg sacs and place them in the greenhouse in the fall so I will have all those great little spiderling predators eating pests in early spring.
The breeding behavior is fun to watch if you happen to catch it in process. The males sneak up on the females and ask to be let into the web. Like many spiders, they can easily be mistaken for food by the larger females. There is a fair amount of cautious questioning, plucking web strings, and making intentions known. Then, there is a brief and frantic interaction with tentative touching and tapping, and then a frantic deposit of sperm and escape. I caught a bit of the dance on video one time while I watched it unfold on our patio.
These spiders are not considered dangerous to humans, and I have had hundreds of them on my person over the years after accidentally walking through their webs, and have never, to my knowledge, been bitten. Along with egg sacs, I will sometimes pick up fat females with my bare hands late in the season and move them to the greenhouse.
The most impressive aspect of these spiders is their amazing web engineering. Sometimes the web spans what seems an impossible gap in the garden, six, eight feet, or more. Watching how they repair/improve the web every day is inspirational. Seeing a perfect web dripping with dew is an elegant sight of which I never tire.