Smorgasbord of Orbs

Of the four common types of spider webs, the orb web is the classic spiderweb.

Its engineering beauty and perfection is unrivaled in the animal kingdom. Orb webs are composed of four basic parts: the frame, the radial threads (spokes), the hub, and the sticky spiral. Only the spiral is sticky. Spiders have the ability to use several different types of silk for different purposes. Orb weaving spiders have 3 claws at the end of their legs which help them walk along their webs without getting stuck.

In Western PA, the month of September reveals a variety of orb weaving spiders. Webs can be quite large and tend to stand out, especially when they take up residence near a porch light (pretty smart). Many of the orb weaving spiders we are noticing now are the full grown adults from this past spring. They didn’t just show up, they’ve been around all this time as smaller, less conspicuous versions of themselves.

My story begins with a common, popular species, the Spotted Orb Weaver AKA Arboreal Orb Weaver (Neoscona crucifera). Of all the ID inquiries I’ve received in the past few weeks, this is THE number one visitor. I would say half of the inquirers are pleasantly curious and the other half are terrified.  Neoscona crucifera is mature right now and full grown, so they are large, heavy spiders. Their webs can measure a few feet across and seem to appear out of the shadows since they weave at night and hide during the day. Aside from their largeness, this is a harmless, shy spider. I had my very own N. crucifera a few weeks ago. The web was in the garden stretching from a tomato plant to nearby tree branches. It was huge, around two feet wide and three feet long, vertically. It was also old, not yet rebuilt, with gaping holes, and small aerial debris. The spider was not in the web, but experience led me to follow one of the thicker frame threads to a curled leaf. And there she was resting during the daylight after, judging by the web damage, a productive night of flying bug feasting.

These spiders rebuild their webs each evening because the stickiness wears off. I’ve also observed them balling up the old web silk and eating it. Watching these spiders construct their webs is an amazing sight! It can take an hour to build! I highly recommend taking the time to watch one. It’s like meditation.

 

I have sometimes misidentified this spider with another kind of orb weaver, the Cross Orb (Araneus diadematus). They are of similar shape and size and occur in late summer/fall around Pittsburgh. However, the Cross Orb weaver lacks the bright orange inner leg segments that Neoscona possesses which you can’t see when the spider is huddled up. The Cross Orb Weaver can often have humps on its abdomen that look like shoulders, plus they almost always have the namesake white cross pattern on the abdomen which N. crucifera lacks. Overall, the Cross Orb weaver seems to have more crisp, bright markings while N. crucifera looks fuzzy and dull. Here are more photos of the Cross Orb Weaver on Bugguide.net since the only one I have is blurry.

I ended up capturing the  N. crucifera spider in my backyard and then felt bad that I couldn’t house it properly (the sides of an Utz pretzel container are too smooth for the spider to grasp), so I let her go onto my fire escape hoping she would build a web out there. This spider was quite resistant to gentle prodding during transfer. When she was huddled up, she would remain frozen that way to the point where I nearly had to pry her off of the leaf. Only at that time did she burst into an escape frenzy to get away. She did not try to run up my arm and bite my eye or anything crazy (some folks associate large with aggressive). Once she was in flight mode, she was hard to scoop up! This type of freeze-flight behavior is why this spider had survived the season! Good girl!

I never did see her again after that and quickly regretted letting her go. Since N. crucifera is so common, I began to rethink container design and actively started looking for another specimen. It has been my experience that I hardly ever find a specific spider when I’m looking for one, but here’s what I did find…

Looking for spider webs is best done on a sunny day because you can see the webs easily. I went to Duff Park in Murraysville, PA to find another N. crucifera. Duff Park is a beautiful chunk of woods (148 acres) that runs along Route 22 and Turtle Creek. I did not find N. crucifera. Of course, they are nocturnal, so I knew to investigate curled up leaves and other good hide outs. It was interesting that N. crucifera seems to be more common around homes than out in the woods.

Across the trails and high in the trees, I saw several Spiny Micrathena (Micrathena gracilis) spiders. They are active during the day and have crazy, spiked abdomens that resemble medieval armor. These spiders are definitely forest dwellers. I don’t recall finding any of these guys in yards. Their orb webs are often high and compact with long anchoring threads that are several feet long. They make a tight spiral and usually have a “free zone” or space between the hub and the spiral.

You cannot confuse Micrathena gracilis for any other spider around here. And if you’re a woodsy person, you’ve probably run into their webs a whole bunch of times because they tend to be across open spaces like trails.

As ominous as they look, they are totally harmless. The tips of their cumbersome abdomens are not endowed with venom and they do not readily bite. Off of their webs, they are painfully awkward and can hardly walk upright. There is much stumbling and rolling onto their backs while their short legs try to grab onto something with texture. In the web, they are graceful and smooth like trapeze artists.

The Funk Bikeway runs along the northern border of Duff Park. Out in the open along the trail fence bordering the creek, I found another stunning orb weaver, what I’m 90% sure was the Marbled Orb (Araneus marmoreus). 

She wasn’t as large as N. crucifera and her web was much smaller, no more than a foot in diameter. The Marbled Orb Weaver pattern reminds me of a tribal mask and they are usually brightly colored. I don’t have a lot of first-hand experience with this spider save for finding them on hikes, always in early autumn. They tend to hide in a curled up leaf next to their web with one leg holding a thread like a fisherman.

Keeping large orb weavers is a challenge because of the space they require for their webs in addition to proper humidity levels, so I tend to leave them alone to continue their short life cycles. However, my curiosity takes over especially when friends, colleagues, and family motivate me by sending pictures and questions.

Back to Neoscona crucifera, the most asked about spider at this time. I DID acquire a live female from a friend who knew I was looking. It was, guess…in his garden. The very night I had her, she produced an egg sac in her small, temporary enclosure.

The silk mesh of the egg sac is a few inches across and there could be hundreds of eggs in there. Naturally, the egg sac would be just fine outside through the rest of autumn and winter. Spiderlings are due to appear in spring. The mom spider may hang around the egg sac for a bit, but her job is officially done and she will die by first frost. These babies are on their own. Since the sac wasn’t secured in a good place (the lid of a solo container) it could be susceptible to predation and parasites if I just put it outside. I’m still juggling the experiment…inside or out. I have since separated mom into a modified-for-orbs Utz pretzel container. I cut out windows and covered them with screen and glued burlap strips and twigs to the lid and sides leaving the center of the container completely open. The next morning, I was very pleased to see that the spider had made, a small, but complete orb web and was sitting in the hub.

In conclusion, I hope you enjoy the smorgasbord of orb webs this autumn! There are many weavers I did not mention that are out there for you to discover. I hope you take the time to get to know, and identify some of these beautiful spiders!