Tay Meadows Tidbit – Marbled Orbweaver

Marbled Orbweaver, Araneus marmoreus

A couple of days ago, as we were relaxing in front of the tv in the evening, Raven suddenly got up and walked to the back of the room, where she started growling. Normally when she does this it’s because she’s heard something outside, or seen a reflection in the window that looked suspicious. But this time she was staring at the wall. After a moment she went up to the wall and snapped at something. That’s when I finally saw the spider. I have no idea how I missed it initially, because it was BIG. Its abdomen was nearly spherical, and about as wide as my thumbnail. I told Raven to sit and wait while I hurried off for my camera. I took a few photos, then caught it in a container to keep overnight – it was below freezing outside by that point, and I wasn’t sure that if I put it outside it wouldn’t just freeze to death shortly after. I let it go the next day, and took the opportunity to take a few more photos in daylight.

Marbled Orbweaver, Araneus marmoreus

The spider is a Marbled Orbweaver, Araneus marmoreus, and is actually a species I encountered at the old house, as well, very close to this time of year. I blogged about it October 20th; it had been crawling across the road when I’d taken Raven out for a walk. I can still recall the spot where I found it. The species is found across Canada and the eastern US, with the majority of records from BugGuide.net submitted in September and October, persisting into November for some of the states southward of me. The species is incredibly variable, with individuals ranging from bright orange (like I found last year) to pale with a huge dark spot (such as this one), bright yellow or white with dark markings to nearly completely dark.

I don’t think that the morphs are specific to particular regions, although all of the pale-with-dark-blotch individuals submitted were from boreal or Shield-edge regions of Canada and Alaska. Interestingly, I made a note in last year’s post that the pale-with-dark-blotch morph was restricted to Eurasia; evidently I was obtaining my information last year from a source other than BugGuide.net. Maybe it meant the form was only found naturally in Eurasia, and individuals in North America have been introduced through international commerce. I think this one arrived at our house on a large potted Norfolk Pine that my mom had left sitting outside all summer.

Today at Kingsford – Marbled Orbweaver

Marbled Orbweaver

I took Raven out for her regular walk this afternoon. I took my camera with me even though it was overcast and threatening to rain, since you never know what you might come across. Thank goodness I did, or I would’ve missed documenting this wild spider. It was walking across the road, and both its size and colour made it exceptionally eye-catching on the bare surface. It was huge. Its abdomen was about the size of my thumbnail. I have no idea why it was crawling across the road, but I couldn’t resist pausing to run off a series of photos.

Marbled Orbweaver

Such a distinctive spider was pretty easy to ID. I already knew it was an orb weaver because of the giant abdomen, and shortened third legs. A search for “orange orb weaver” on BugGuide.net turned up a bunch of photos, including several of my critter. It’s a Marbled Orbweaver, Araneus marmoreus, a fairly common spider of woodland clearings and long-grassed meadows. It’s been recorded in all of the Canadian provinces, with the majority in the more open southern Ontario and prairie provinces. There aren’t many records from the US on that page (it is CanadianArachnology.org, after all), but BugGuide.net shows records for most of the eastern states. Worldwide, it’s a holarctic species, found in Eurasia as well.

Marbled Orbweaver

Its abdomen is intricately patterned, almost looking like bubbles, but the thing that I thought was particularly neat is that the pattern is asymmetrical, especially right at the front. There’s actually two morphs of this species, this one (which can also come in yellowish versions with dark markings), and one whose abdomen is mostly pale with a large dark blotch at the back. The latter form is only found in Eurasia, and rarely overlaps in range with the orange version. How they know they’re the same species is a mystery of science. The large size makes this a female. Females can reach 14mm (body size minus the legs) while males are much smaller, reaching just 9mm. Being a member of the Araneus it ought to show a longitudinal crease down the abdomen (as opposed to Neoscona, which has horizontal creases), but if there were any creases at all, they weren’t visibly obvious to me.