On the morning of October 3rd, I was getting ready to leave Lake Tawakoni State Park. An orbweaver, Neoscona crucifera, had attached its web to my popup A-frame camper. I didn’t want to simply drive away and risk taking the spider with me or separating the spider from its web, so I manually detached the web. That way, the spider could recycle the web for use the next night by eating it.
Before taking the web down, I noticed that it was full of midges. I’m guessing that the midges were too small for the spider to notice or perhaps too small to bother eating. (She was a big spider!) But when I returned after walking my dogs, she had rolled up the midges into a giant midgeball. Meanwhile, she was eating the balled-up remains of the rest of the web. By the time I got my camera out, she had begun munching on the midgeball. Check it out:
Because the long-jawed orbweavers in the giant web were primarily active at night, I would often be out walking the trails at night. Orbweavers such as N. crucifera would emerge after nightfall in profusion, making orb webs everywhere, large and small. I would do my best to avoid wrecking the webs as I travelled, but occasionally there’d be a mishap.
Orb webs frequently have three anchor points. The larger N. crucifera would typically have long lines extending from the web to one or two of these points. Over the trails, one anchor point would often be on the ground, sometimes in the middle of the trail. If the light from my flashlight didn’t hit the line just right, I’d fail to notice it. If the spider was unlucky, I’d plow straight through it.
The webs are strong and I’d generally know when I’d broken a web. One time I accidentally broke a line and looked up to see an enormous orb web now waving loosely in the breeze. I figured the poor spider would have to eat the web and rebuild it entirely. But as I watched, the spider immediately went to work. I had broken a ground anchor, and the spider rapidly climbed to an overhead anchor. I wrongly assumed that I had scared the spider and that she was seeking refuge in her retreat. Within seconds of her reaching the highest point on the anchor, I saw the loose web make two strong jerks in the direction of the spider, and suddenly the orb was taught again, even if only half its original size. The spider had shortened the overhead anchor line to tighten up the web!
Another time I was out walking my dogs. I tried to skirt the dogs around a ground anchor of another large web, also N. crucifera, but the leash on one dog quickly clipped the line. This time I knew to sit and watch.
Instead of racing up the web, the spider cautiously worked her way down to the corner where the line had been cut. When she got to the corner, she dropped a ways on the now-loose anchor line. She was a big spider, and her weight helped to keep the web from blowing in the breeze. If the web touches itself as it blows, the sticky spiral lines of the web will cause it to stick to itself like tape, and just as this can wreck a length of tape, it can wreck a web. As she dangled in that corner, her weight helped keep this from happening.
But she wasn’t just sitting there. She was quickly reeling in the broken anchor line. She balled it up and swiftly devoured it. Then she dropped to the ground, landing in virtually the same place where the web had originally anchored. She attached a new anchor line. By the time she returned to the web, the web was once again taught and hardly showed any signs of my dog having wrecked it. Only about a third of it was distorted and partially collapsed. The web remained perfectly usable and would last her the night.
If this isn’t intelligence, I don’t know what is. Maybe spiders are programmed to behave this way in their genes, but I still think it makes them smart.