October is clearly orb weaver month, and not just here on the farm. Suddenly out of nowhere it looks as if Nature herself has decided it’s time to decorate for Halloween. There are spiders, and their webs, all over the trees, and shrubs, and every morning the woodlands seem to be draped with new webs. We won’t need any fake spider webs for decorations this year!
This week the Cross Orb Weaver (Araneus diadematus) seems to be the most prevalent species here, both in the garden, and around the house.
I’ve found many individuals of this species, in various stages of maturity, lurking in the shrubbery, or hiding underneath the patio umbrella in recent weeks.
Most mornings on the way to the garden I find myself inadvertently walking through at least one web that I didn’t see. It may sound strange, but I always feel a little bad damaging one of these webs.
I’m in awe of spiders as architects, and can’t honestly imagine the effort it must take to carefully construct a new web each morning in the hopes of catching a meal.
Araneus diadematus is not a native North American spider species. That said, it is clearly well adapted to living here, so much so that it is considered to be an invasive spider species in the Bay Area. The Cross Orb Weaver is originally from Northern Europe, and became established along the Pacific Coast in the 1970s. Due to its origin, another common name for this species is the European Garden Spider.
This morning, outside the kitchen, under the patio umbrella, is this sizable, very mature, female.
I’ve been watching her for a few days now.
Each morning she crafts a web that’s almost 2 feet across, close to 5 feet if you count the bridging and tether lines that suspend the web.
She then waits for a passing meal.
I’m actually thrilled she’s there, as this morning I watched her catch breakfast, and it was a yellow-jacket wasp!
We clearly have a formidable wasp nest somewhere near the house, but I have yet to locate the entrance.
I was stung, unprovoked, on Friday morning, through two layers of clothes, which resulted in a lot of swearing, and an increased level of wariness on my part. Despite having a number of yellow jacket traps around the property, there are dozens of them buzzing around near the back door, so any help we can get to keep their populations down is appreciated!
It seems that these spiders are quite fastidious, and after watching them for the last few days, each time prey is captured, it is quickly removed from the center of the web. Perhaps this is to make the web less obvious to other insects flying by?
Just as I was getting ready to leave, I noticed an immature female on the other side of the patio umbrella. No sooner had I spied her, than another yellow jacket met its doom!
Even if you’re scared of spiders you can see that they are hard-working, beneficial creatures in the garden, preying on pests, so please leave them be, and don’t squish them.
Moving beyond the patio, I recently bumped into a male and female pair in the herb garden, consisting of an immature female, and a mature male. Side by side it’s obvious that the males and females of this species are a different shape. Mature females are more rounded in appearance, and grow to 20 mm in length, almost twice the size of the smaller males.
The female had successfully captured a honey bee, and cocooned it in silk. Lurking just below her in the oregano was a male.
The markings weren’t as prominent on this female, and she was more equal in size to the male. If this was a mature female, she’d dwarf him in size.
Late summer to early autumn is breeding season for these spiders. I wondered if the male was perhaps a potential mate, so I waited to see what transpired.
Courtship for male orbweaving spiders is a dangerous game. One misstep, and the male will meet the same fate as the bee.
The male would approach cautiously, and when just barely within reach, he’d touch her. She’d immediately raise her legs and dart toward him, which sent him scurrying in retreat.
After a while it became apparent that perhaps this male was less interested in her, and more interested in her prize.
Eventually the female retreated underneath an oregano branch, leaving her prey unguarded. The male then slowly approached the bee.
However, as soon as he was within reach, he knocked it loose, and the bee fell down into the dirt below. I could almost hear the female cursing at this male for being such a klutz!
With the bee gone, after a few minutes the male continued his approach toward the female.
There was a lot of leg-waving, cautious approaches, and hurried retreats, but mostly the female seemed to ignore the male’s advances.
It was already early evening, and the light was fading, so I chose to wait and check in on them again in the morning.
The next morning though, both spiders were gone. Perhaps the female constructed her web elsewhere in the garden that morning, or perhaps they both became prey for a hungry bird. Regardless, that was the last I saw of this pair. This immature female likely wouldn’t reproduce this season, and as a juvenile, she may overwinter in the garden, to breed next season.
Between now and November the mature females that survive, and mate, will begin to construct their egg sacs. They will then stay with their eggs to guard them, but will cease foraging, until eventually they die in the late autumn to early winter.
Earlier this spring I’d found some recently hatched orb weaver spiderlings, and at the time I had presumed they were most likely Araneus diadematus species. As the females that produce the egg sacs don’t survive winter though, I wasn’t able to find any of this species in the spring. This autumn though, it’s obvious we have a healthy population of them on the farm. Now that I’ve noticed so many females here this fall, I suspect the spiderlings were indeed Cross Orb Weavers, and maybe we’ll find more spiderlings hatching here next spring.
There’s no question we’ll have more yellow jackets next season!
 KQED Quest: Spider Invaders by by Jennifer Skene Oct. 2010